Radiochemistry - introduction

Prévia do material em texto

t
By D. S. URCH 
Department of Chemistry, Queen Mary College, University of London, Mile End Road, 
London El 4NS 
1 Introduction 
Radiochemistry is an area of chemical activity which most people understand in a 
general way but which few would care to define. Decades ago it was perhaps easier 
and any chemical investigation that involved radioactivity in any way was obviously 
radiochemistry. The techniques of radiochemistry have now, however, diffused into 
chemistry as a whole; tracer methods are commonplace for following reaction 
mechanisms, actinide chemistry is part and parcel of inorganic chemistry, and 
radioactive compounds have found a use, not only in almost all branches of 
chemistry, but in physics, biology, engineering, and medicine as well. Clearly a 
review of radiochemistry for 1977-79 should no longer concern itself with such a 
broad canvas and this Report will deal with those topics in which the radioactive 
nature of a particular atom is of primary importance. Broadly speaking, this means 
that two main areas will be covered: 
(i) Chemical techniques for the production and/or separation of specific isotopes 
and 
(ii) Chemistry associated with nuclear transformations including those brought 
but the following will be excluded, except where points of radiochemical interest 
arise: 
about by radioactive decay, 
(i) General actinide chemistry 
(ii) Radiation chemistry 
(iii) Isotopic separation techniques 
(iv) Nuclear medicine 
(v) Labelled compound formation 
2 Specific Isotopes 
Nitrogen.-Fast neutron irradiation of ammonium compounds or charged particle 
bombardment of oxygen-containing species (water, oxoanions) can initiate the 
(n*,2n)' and ( 1or2H,a)2,3 reactions respectively to give "N. Depending upon the 
conditions and associated radiation dose, the nitrogen activity is found in a variety of 
chemical forms;lb e.g. (n*,2n) in ammonium sulphate gave 50% I3N as dinitrogen 
( a ) A. H. W. Aten and J. C. F. Michielsen, J. Inorg. Nuclear Chem., 1978,40, 1700; ( 6 ) A. H. W. Aten 
and J. C. Kapteyn, Radiochem. Radioanalyt. Letters, 1978,32,83. 
G . S . McNaughton and R. D. More, Intemat. J. Appl . Radiation Isotopes, 1979,30,489. 
K. A . Krohn and N. J. Parks, J. Labelled Compounds Radiopharm., 1979,16,87. 
247 
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248 D. S, Urch 
whereas ['H(2 MeV), a] on lithium carbonate solutions produced' mostly labelled 
NO3- with some NO2- and CN-. I3NH4+ is not usually produced directly in these 
experiments but can be made by reduction3. Gaseous l3NI4N, for medical use, can be 
made by hypobromate ~x ida t ion .~ 
Oxygen.-Water and alcohols labelled with I5O (7; = 120 s) have been produced 
directly from the 14N(d,n)150 reaction by deuteron irradiation of nitrogen, hydrogen, 
or hydrocarbon mixture^.^ Even 140H2 ( 1 4 0 , 71 = 70 s) has been synthesized for 
medical use.6 
Fluorine.--"F has a convenient half-life (1 10 min) for many research applications 
and can be produced by a variety of nuclear reactions. Japanese workers' have 
recently developed a gas-phase photonuclear process based on 20Ne(y,pn)'8F and 
Ne(y,2n)18Ne + "F, and techniques for ''F production from thermal neutron 
reactor irradiation of lithium. carbonate have also been described' [l'F is formed via 
the nuclear reaction of high-energy tritons, 6Li(n,a)3H, with 1 6 0 1 . 
Sodium and Magnesium.-The formation of 24Na and 28Mg from a variety of targets 
using proton bombardment (50-180 MeV) has been ~ t u d i e d , ~ 
Phosphorus.-Although the long-lived 33P can be conveniently prepared by reactor 
neutron irradiation of sulphur enriched with 33S,10 the short-lived 30P (71 = 2.5 min) 
is much more attractive for medical applications. A variety of nuclear reactions 
r31P(n,2n), 32S(n,t), 27Al(d,n), and 31P(p,pn)] for the production of this isotope has 
been studied by Stocklin and his co-workers.l' 
Manganese and Ir~n.-'~Fe is the isotope of iron with the greatest potential for 
medical use (i.e. its annihilation y-rays can be used in tomographic imaging proces- 
ses). It can be prepared by cyclotron proton bombardment of manganese or nickel 
targets." Short-lived 52mMn, which is also a' positron emitter and therefore with 
medical potential, is formed in the decay of 52Fe. 56Mn can be extracted from 
neutron-irradiated iron sulphide with amm011ia.I~ 
Cobalt.-"Co (T;= 18.5 h) can be used to label molecules of biochemical interest 
(e.g. ble~mycin)'~". This isotope can be made either from iron'4a [56Fe(p,2n)] or 
from [55Mn(3He,3n)]. 
20 
' L. Lindner, J. Helmer, and G. A. Brinkman, Internat. J. Appl. Radiation Isotopes, 1974,30,506. 
H. V. Ruiz and A. P. Wolf, 9th International Hot Atom Symposium, Virginia Poly Inst., U.S.A. 
Abstracts, 1977, pp. 13, 69. 
R. J. Nickles, S. J. Gatley, M. T. Madsen, R. D. Hichwa, J. L. Martin, D. J. Simpkin, and J. R. Halama, J. 
Labelled Compounds Radiopharm., 1979,16,90. 
'I M. Yagi and R. Amano, Kakuriken Kenkyu Hokoku, 1979,12,116. 
* H. T. Gasiglia and C. P. Concalves da Silva, Publ. Z.E.A., 1978, p. 501. 
lo G. N. Shapkin and A. I. Egorov, Radiokhimiya, 1977,19, 876. 
l 1 S. M. Sahakundu, S. M. Qaim, and G. Stocklin, Internat. J. Appl. Radiation Isotopes, 1979, 30, 3. 
l2 T. H. Ku, P. Richards, L. G. Stang, and T. Prach, Energy Res. Abs., 1979,4, No. 41 386. 
l3 Z. B. Alfassi, Radiochern. Radioanalyt. Letters, 1978,32, 321. 
H. Lundqvist and P. Malmborg, Internat. J. Appl. Radiation Isotopes, 1979, 30, 33. 
( a ) M. C. Lagunas-Solar and J. A. Jungerman, Internat. J. Appl. Radiation Isotopes, 1979,30,25; ( 6 ) M. 
Watanabe, K. Horiuchi, H. Nakahara, and Y. Murakami, J. Labelled Compounds Radiophann., 1979, 
16,216; ( c ) M. Watanabe, H. Nakahara, and Y. Murakami, Internat. J. Appl . Radiation Isotopes, 1979, 
30,625. 
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Radiochemistry 249 
Copper and Zinc.-Yields of or 62Zn from nickel could be optimized by varying 
the bombardment energy of the a -particles (21 and 35 MeV re~pectively)'~ and 67Cu 
can be produced from 682n by y-irradiation.16 
Gallium.-The irradiation of zinc with a or 3He particles generates isotopes of 
gallium. 67Ga was produced most efficiently by a-19 MeV.17 Techniques for 
extraction of both 67Ga and 68Ga have been described.18 
Arsenic and Selenium.-The short-lived isotope of selenium 73Se19 is formed when 
natural germanium (or 72Ge enriched) is bombarded with a or 3He particles.20 When 
this isotope has decayed away, 72Se can be isolated and used as a source of 72A~.21 
Reactor irradiation of germanium (thermal n flux 1013 n cm-l) on the other hand 
gives rise to 77As.22 
Bromine.-Proton bombardment of sodium bromide generates 77Kr, the decay of 
which forms 77Br.23 The same isotope," which has radiopharmaceutical uses, can be 
produced by the [75As(a,2n)77Br] reaction using copper arsenide as a target.24 87Br 
can be isolated25 from the fission products that result from thermal neutron irradia- 
tion of 2 3 5 ~ . 
Krypton.-Convenient techniques for the generation of ""'Kr from "Rb have been 
developed by Wolf and his co-workers using 820r83Kr(p, 2 or 3n).26 
Yttrium.-"Sr adsorbed on to Amberlite-IR-120 resin can be used as a source of 
M~lybdenum.-~'Mo can be extracted from molybdenum trisulphide after thermal 
neutron irradiation.28 Methods for the extraction of radioactive molybdenum from 
fission products of neutron-irradiated uranium have also been de~cribed.~' Proton 
irradiation of silverchloride gives rise to a wide variety of neutron-deficient nuclei 
from which Mo isotopes can be isolated.30 
Technetium.-Methods for producing ''"'Tc from 99M031 and for estimating the "Tc 
content of ''"'Tc preparations have been described.32 
Y. The daughter isotope can be eluted with edta.27 90 
H. Muramatsu, E. Shirai, H. Nakahara, and Y. Murakami, Radioisotopes, 1978, 27, 636. 
M. Yagi and K. Kondo, Internat. J. Appl. Radiation Isotopes, 1978, 29,757. 
Y. Nagame, M. Unno, H. Nakahara, and Y. Murakami, Radioisotopes, 1978,27, 631. 
R. D. Neirinckz and M. A. Davis, J. Labelled Compounds Radiopharm., 1979,16,109; P. Grychowski, 
S. Kopta, J. Mikulski, E. Ochab, and T. Petryna, Radiochem. Radioanalyt. Letters, 1979,39, 151. 
l9 T. Nozaki, Y. Ito, M. Iwamoto, and K. Ogawa, J. Labelled Compounds Radiopharm., 1979,16,219. 
'O M. Guillaume, M. Lambrecht, and A. P. Wolf, Internat. J. Appl. Radiation Isotopes, 1978,29,41. 
'' S . H. Al-Kouraishi and G. G. J. Boswell, Internat. J. App l , Radiation Isotopes, 1978, 29, 607. 
22 A. A. Zhuravlev, T. Bigeliene, and 0. A. Abrarov, Radiokhimiya, 1978,20, 623. 
23 ( a ) H. Lundqvist, P. Malmborg, B. Langstrom, and S. N. Chiengmai, Internat. J. Appl. Radiation 
Isotopes, 1979,30, 39; ( b ) M. Diksic, J. L. Galinier, H. Marshall, and L. Yaffe, ibid., 1977,28, 885. 
24 R. Weinreich and G. Blessing, J. Labelled Compounds Radiopharm., 1979, 16, 222. 
'' P. K. Ray and E. S . Kenney, J. Radioanalyt. Chem., 1978,42,367. 
26 T. J. Ruth, R. M. Lambrecht, A. P. Wolf, and M. L. Thakur, J. Labelled Compounds Radiopharm., 1979, 
" W. J. Skraba, H. Arino, and H. H. Kramer, Internat. J. Appl. Radiation Isotopes, 1978, 29,91. 
'* M. Kis and E. Edgner, Doga, 1978,2,239. 
29 M. Iqbal and M. Ejaz, J. Radioanalyt. Chem., 1978, 47, 25. 
30 ( a ) B. Bayar, A. F. Novgorodov, I. Vocilka, and N. G. Zaitseva, Radiochem. Radioanalyt. Letters, 1978, 
31 V. L. Levin, L. S. Kozyreva-Aleksandrova, T. N. Sokolova, and V. G. Zalesskii, Radiochem. Radioana- 
32 K. Svoboda, V. Husak, J. Vlcek, and F. Houdek, J. Labelled Compounds Radiopharm., 1979,16,122. 
16,210. 
35, 109; ( 6 ) B. Baier, J. Vocilka, and N. G. Zaitseva, J. Inorg. Nuclear Chem., 1978, 40, 1461. 
lyt. Letters, 1979, 39, 141. 
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250 D. S. Urch 
Ruthenium and Rhodi~m.-~’Ru (7; = 68.13 h) can be prepared by the bombard- 
ment of natural molybdenum with a particles;33 it is also formed, along with 92R~, by 
the proton bombardment of Proton bombardment of palladium is a useful 
source of 1°lrnRh, which is used in tumour location in mice.34 
Tin.-Carrier-free 117rnSn can be prepared from the a -particle bombardment of 
1 1 5 1 ~ . 3 5 
Iodine.-Radiopharmaceutical and biomedical interest in iodine now centres largely 
on 1231 because of its favourable nuclear properties. 1231 is formed when ‘23Xe decays 
and this isotope of xenon can be made by the proton bombardment of natural iodine 
[1271(p,5n)123Xe].23”,36 The 1231 produced from the 123Xe can be stored as either 
sodium iodide or iodine monochloride; alternatively exposure of potassium iodate to 
Xe can produce a potent reagent from which a wide variety of compounds 
labelled with radioactive iodine can be made.37 1231 can also be produced by proton 
(26 MeV) bombardment of tellurium, i.e. [124Te(p, 1241 results when the 
proton energy is reduced to 12 MeV.38 Neutron-rich isotopes of iodine result from 
reactor-induced fission of uranium; irradiation of uranyl acetate solutions usually 
gives about 60% of the iodine activity (134m, 134.. . 1-37) as iodide ions and the 
remainder as iodate.39 
123(or 125) 
Barium.-Fission-produced 137Cs can be used as a source for the short-lived 
(71 = 2.6 min) 137rnBa 
Lanthanides.-Cation exchange at 80 “C by elution with a -hydroxyisobutyric acid 
can be used to separate 179*177Lu, 17’Yb, 173Tm, 172s171Er, l6’Ho, and 161*160.rt) 
produced by uranium fission.41 Proton bombardment of rare-earth oxides by 
contrast gives rise to neutron-deficient isotopes which can be extracted as volatile 
P-diketonate complexes.42 Various techniques for the separation of 144Pr from its 
parent 144Ce have recently been described, e.g. zirconium phosphate ion-exchange 
reversed-phase chromatography on Kieselguhr impregnated with 
Aliquat-336,44 and a column of alumina coated with magnanese di~xide.~’ In 
all cases the cerium was adsorbed and the praseodymium could be eluted as 
required. 
33 D. J. Silvester, F. Helus, and W. Maier-Borst, J. Labelled Compounds Radiopharm., 1979,16, 226. 
34 M. C. Lagunas-Solar, S. R. Wilkins, D. W. Paulson, C. J. MacKenzie, and K. A. Krohn, J. Labelled 
3s B. Z . Iofa, L. N. Makagonova, and Yu. G. Sevast’yanov, Radiokhimiya, 1978,20,156. 
36 M. C. Lagunas-Solar, J. A. Jungerman, N. F. Peek, and W. C. Bennett, J. Labelled Compounds 
’’ H. J. Machulla, A. Shanshal, and G. Stocklin, Radiochim. Acra, 1977, 24.42. 
Compounds Radiophann., 1979,16,229. 
Radiophann., 1979,16,224. 
K. Kondo, E. R. Lambrecht, E. F. Norton, and A. P. Wolf, Internat. J. Appl. Radiation Isotopes, 1977,28, 
765. 
39 H Tekemi, Y. Koso, R. Matsushita, J. Takada, and T. Tamai, Radiochem. Radioanalyt. Letters, 1978, 
36,381. 
40 N. Rarnamoorthy, M. Krishnamoorthy, and R. S. Mani, Radiochem. Radioanalyt. Letters, 1977,31,251. 
V. K. Bhargava, V. K. Rao, S. G. Marathe, S. M. Sahakundu, and R. H. Iyer, J. Radioanalyt. Chem., 
1978,47, 5 . 
42 E. Herrmann, G. J. Beyer, M. John, W. D. Fromm, and V. A. Chalkin, Isotopenpraxis, 1978,14, 280. 
43 D. K. Bhattacharyya and S. Basu, J. Radioanalyt. Chem., 1978.47, 105. 
44 S. N. Bhattacharyya and S. Sarkar, J. Inorg. Nuclear Chem., 1979, 41, 755. 
*’ W. J. Skraba, H. Arino, and H. H. Kramer, Internat. J . Appl. Radiation Isotopes, 1978,29, 578. 
41 
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Radiochemistry 25 1 
Tantalum.-Proton (34 MeV) bombardment of natural tantalum gives the tungsten 
isotope "'W. Once the isotope has been chemically separated, the 17'W decay can 
be used as a source of the short-lived isotope 178Ta (7; = 9.3 ~ n i n ) . ~ ~ 
Gold.-From the alchemic point of view it is unfortunate that transmutation 
reactions to produce gold by neutron bombardment require platinum and not lead as 
a starting material. The gold (199A~) that is produced4' can be extracted in a 
carrier-free state using l-phenyl-3-methyl-4-trifluoroacetylpyrazol-5-one or by 
~hromatography.~~ 
Thallium.-Techniques for the production of carrier-free 201Tl from deuteron 
bombardment of mercury have been de~cribed.~' 
Lead.-Solvent extractionSo and ion-exchange techniques5' have both been advo- 
cated for the separation of '03Pb from the thallium targets in which it was made by 
charged-particle bombardment. 
Bismuth.-Carrier-free 210Bi can be separated from its parent '"Pb by either 
adsorbing the latter as molybdate on a silica gel or by using zirconium 
phosphate as an ion-exchange 
Radium.-Ion-exchange chromatography can be used to separate 228Ra from 
natural thorium (as ~ x a l a t e ) . ~ ~ 
Actinides.-The preparation of pure 230Th has been described.54 This isotope can be 
used as a source for both 231Pa and 232U (of use in radionuclide batteries). The 231Pa 
can be separated from thorium by solvent extractiod5 or ~hemically.~~ Heavy-ion 
bombardment of uranium gives rise to a series of actinide isotopes which can be 
separated by cation- or anion-exchange chromatography or by using a silica gel 
column.57 Californium, 252Cf, can be used as a starting point for the production of 
Fm, via 2 5 3 E ~ and 253mE~ (T;= 3.9 h). The elements can be separated using 
ammonium cy -0xyisobutyrateas a chromatographic el~ant.~'" 256Md can be pre- 
pared from 2 5 3 E ~ by bombardment with 28 MeV cy particle~.~'~ 
254 
3 Chemical Effects of Nuclear Transformations 
It is a pleasure to be able to report the appearance, albeit at vast cost, of the long 
awaited book on the inorganic chemistry of nuclear transformations by Harbottle 
46 B. L. Holman, G. 1. Hams, R. D. Neirinckx, A. G. Jones, and J. Idoine, J. NuclearMed., 1978,19,510. 
47 S . M. Hasany, I. Hanif, and 1. H. Qureshi, Internat. J. Appl . Radiation Isotopes, 1978,29, 145. 
4a M. Y. Mina, Radiochim. Acta, 1977,2447. 
49 L. N. Makagonova, B. Z. Iofa, and Yu. G . Sevast'yanov, Radiokhimiya, 1977,19,860. 
" T. V. Toribara and L. Koval, Internat. J. Appl. Radiation Isotopes, 1978, 29, 196. 
51 N. Ramamoorthy and L. A. Watson, Radiochem. Radioanalyt. Letters, 1979,39, 309. 
" D. K. Bhattacharyya and S. Basu, 1 Radioanalyt. Chem., 1978,44,5. 
53 G. L. de Almeida and A. G . da Silva, J. Radioanalyt. Chem., 1979, 52, 31. 
54 E. Kluge, K. H. Lieser, I. Loc, and S. Quandt, Radiochirn. Acra, 1977,24,21. 
'' A. T. Kandil and A. Ramadan, Radiochim. Acra, 1978,25,107. 
56 D. Brown and B. Whittaker, J. Less-Common Metals, 1978, 61, 161. 
'' M. Schaedel, W. Bruechle, B. Haefner, J. V. Kratz, W. Schorstein, N. Trautmann, and G. Herrmann, 
Radiochim. Acra, 1978,25, 111. 
( a ) N. B. Mikheev, I. A. Rumer, A. N. Kamenskaya, and A. M. Podorozhnyi, Radiokhimiya, 1978,20, 
333; ( b ) N. B. Mikheev, J. Mikulski, T. Petryna, Z. Szeglowski, I. A. Rumer, and L. N. Auerman. 
Rap.-Znst. Fiz. Jad. (Krakow), 1979, p. 1038/c. 
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252 D. S. Urch 
and Madd~ck.~’ As this book amply covers the historic literature this section will 
concentrate on recent developments which, for convenience, will be classified as 
follows: effects due to the passage of the heavy particles produced in nuclear 
reactions; effects that involve chemical reactions activated by nuclear decay; and 
those chemical reactions that are due to the recoil atoms themselves. 
Recoil Particle ‘Radiation’ Chemistry.-Local concentrations of radicals formed 
along the tracks of recoiling 3H, 4He, and 7Li (formed by neutron irradiation of B203 
or LiC104) in methanol were studied by the addition of cadmium ions as electron 
acceptors and were estimated to be of the order of 3 x lo” cmV3 for both reactions.60 
The much heavier fission recoil particles can also induce considerable chemical 
change in the materials through which they pass; e.g. n-butane can be formed from 
ethylene even in the presence of some oxygen.61 And the yield of N2 from the 
decomposition of N 2 0 can in fact be used to measure the fission recoil dose.62 
Nuclear Decay Chemistry.-Exposure to tritium gas is a very simple way of 
producing labelled molecules. When tritium atoms so formed react with amyl 
halides, tritium-labelled pentane is most readily produced from the iodide and least 
readily from the The kinetics of @ -decay-induced exchange between H2, 
’H2, and 3H2 have been studied. The system H2+3H2 2H3H took twice as long to 
reach an equivalent position as did 2H2+3H2 22H3H.64 The reactions were 
followed using a quadrupole mass filter system. A similar technique6’ was used to 
study the fragment ions produced by the @-decay of 3H in compounds such as 3HH0, 
3H20, CH3CH3HOH, and CH23HOH. The first step would appear to be the 
formation of an ion in which 3He’ is chemically bound. Subsequent reactions follow 
from the fission of 0-He’ or C-H’.66 Free C3H3+ ions would appear to be 
produced by the decay of one of the tritium atoms of C3H4. Their reactions with 
substrates such as toluene and t-butylbenzene have been in~estigated.~’ A 
theoretical study of the effect of the transformation 3H + He’ upon a hydrogen bond 
in systems such as 2HH2N...HNH2 and 3HH2CH2N--.HNH2 has been made; the 
ammonia dimer is predicted to survive.68 Theory has also been used to predict the 
consequences of 18F positron decay in methyl fluoride.69 Leurs70 has made a study, 
both theoretical and experimental, on the chemical effects due to the P-decay, 
S -+ 38Cl, in molecules such as H2S and S042-. In the latter case ca. 2--12O/0 of the 
chlorine was found in oxidation states higher than Cl- whereas recoil 38Cl produced 
by [41K(n,a)38C1] in potassium sulphate was found almost always as chloride. This 
38 
59 ‘Chemical Effects of Nuclear Transformations’, ed. G. Harbottle and A. G. Maddock, North-Holland, 
6o R. L. Samoilova, A. M. Raitsimring, and Y. D. Tsvetokov, Khim. uysok, Energii, 1979.13, 301. 
61 G. G. Meisels, J. A. Laverne, W. B. Richardson, and T. C. Hsieh, J. Phys. Chem., 1978, 82, 2231. 
62 G . G. Meisels, J. P. Freeman, J. P. Gregory, W. C. Richardson, and G. J. Stroka, Radiat. Phys. Chem., 
6 3 Y. N. Simirskii and L. P. Firsova, Radiokhimiya, 1978, 20, 305. 
64 J. W. Pyper, E. M. Kelly, R. T. Tsugawa, P. E. Roberts, and P. C. Souers, Energy Res. A h . , 1978,3, No. 
65 Y. K. Okuma and T. Shiokawa, Radiochem. Radioanalyt. Letters, 1978, 35, 11. 
67 P. Giacomello and M. Scheuller, Radiochim. Acra, 1977.24, 11 1. 
68 S. Ikuta, Chem. Phys. Letters, 1978, 56, 490. 
69 S. Ikuta. Chem. Letters. 1978, 7,781. 
7” C. K. Leurs, INIS Atomindex, 1978,9, No. 378 476. 
Amsterdam, 1979. 
1978,11, 153. 
52 187. 
K. Okuno, M. Kato, K. Yoshihara, and T. Shiokawa, Radiochem. Radioanalyt. Letters, 1979,37, 191. 
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Radiochemistry 253 
suggests that @-decay imparts only a small recoil energy to 38S so that not all chemical 
Co and the @-decay bonds are b r ~ k e n . ~ ’ Isomeric transitions 58m Or ‘Om 
Ni -+ 57C0 would also seem to cause little disruption when the parent atoms are 
bound in tetraphenylporphine complexes.72 The effect of 57C0 decay in cobalt and 
iron nitrosyl complexes was studied using Mossbauer The reactions 
of iodine formed by the decay of fission-produced tellurium with methane and 
methyl halides would appear to be complex,74 but the decay of 132Te in compounds 
such as TeC1, and ( ( Y - C ~ ~ H ~ ) ~ T ~ in chloropentane solutions was much easier to 
follow.75 As might be expected chemical bonds in the latter aromatic compound 
proved the more stable. 
A study of @-decay effects in lanthanide complexes would seem to suggest that 
‘retention’ (i.e. the percentage of the daughter activity found for whatever reason in 
the same chemical form as the parent) can be increased by increasing the viscosity of 
the solvent, presumably by reducing the distance the recoil atom travels from tis 
original 
Chemical Reactions of Recoil Atoms (Including Ions and Excited Species).-The 
energy liberated in any nuclear reaction is carried away as radiation and as trans- 
lational excitation of the daughter particles, their ‘recoil energy’. For the most part 
this energy is lost in ionizing collisions (see previous section), but at the end of the 
recoil track sufficient energy remains for the particle to engage in non-disruptive 
collisions, probably enough energy in many cases to pass over activation energy 
barriers with ease. This is ‘hot-atom’ chemistry, but, more generally, the chemistry 
of particles produced in nuclear reactions can be due not only to translational 
excitation but also to electronic excitation and also to ionization. Recent develop- 
ments (1977-79) in this field will be considered in this section element by element. 
Theoretical studies have greatly assisted an understanding of the often complex 
mechanisms and reference to such work will also be made where relevant. 
co + 58g or 6Og 
57 
Hydrogen.-Detailed theoretical studies of the basicreaction 
3H*+2H’H -+ 3H2H+1H or 3H’H+2H 
have been made77 using sophisticated potential surfaces, and taking inelastic 
collisions into account, but the results do not always agree with experiment. With a 
much simpler basic model based on hard-sphere excitation functions Malcolm- 
Lawes continues to produce successful results, e.g. 3H* + H20,78 3H* + 02,79 3H* + 
CH, or SiH4.80 Poor agreement with experiment was found for SiH4 but this may be 
due to decomposition of excited Si3HH3 molecules. Related experimental studies 
using CH3Si2H3 have shown that deuterium atoms attached to silicon are substituted 
71 C. J. Leurs, J. Boersma, and L. Lindner, Radiochim. Acra, 1977, 24, 155. 
’’ N. Ikeda, H. Shoji, Y. Sakai, and S. Nakajima, Kakuriken Kenkyu Hokoku, 1976,9,253. 
73 Yu. D. Perfil’ev, L. A. Kulikov, M. I. Afanasov, A. M. Babeshkin, and P. P. Ginter, Khim. vysok. Enetgii, 
’4 M. Kikuchi and L. B. Church, Radiochim. Acra, 1977, 24,97. 
7 5 E. G. Alekseev and V. Zaitsev, Radiokhimiya, 1978,20, 142. 
76 T. Assano and S. Taniguchi, J. Inorg. Nuclear Chem., 1978,40,957. 
77 J. S. Wright, S. K. Gray, and R. N. Porter, J. Phys. Chem., 1979,83, 1033. 
78 D. J. Malcolme-Lawes, J. Inorg. Nuclear Chem., 1978, 40, 1455. 
79 D. J. Malcolme-Lawes, J.C.S. Faraday II, 1978,74,696. 
D. J. Malcolme-Lawes, Radiochim. Acta, 1977, 24, 34. 
1978,12, 175. 
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254 D. S. Urch 
almost twice as readily as hydrogens at carbon: again decomposition of recently 
labelled molecules is proposed.81 A detailed study of the vibrationally excited state 
of recently labelled cyclobutane has been undertaken by Spicer and his co-workers.82 
Combining theoretical and experimental approaches they have shown that about 
half of the recoil energy of the tritium is deposited in the vibrational modes of 
cyclobutane when a hydrogen atom is replaced by a tritium. This produces 
[3H]cyclobutane molecules with a wide range of excitation, 56% of which de- 
composes with varying degrees of alacrity to ethylene. The rate at which vibrational 
excitation might be transferred to various bath gases was also determined. In further 
gas-phase studies, it has been found that the addition of nickel carbonyl enhances the 
usually very small yield of [3H]ethylene from the reaction of recoil tritium with 
 paraffin^.'^ In the solid phase the following systems have been investigated: 3H* + 
ha loge no benzene^,^^ 3H* + neopentane-isobutane (77 K)," 3H* + and 3H* + 
Li20, LiOH, and Li2C03;87 from the latter two systems most of the tritium was found 
in labelled water. 
Carbon.-The chemistry of nascent carbon atoms has excited chemists for many 
years but discussion of the mechanisms whereby this quadrivalent species reacts with 
simple molecules has produced much controversy. It is, however, just possible that 
the pathway for the formation of ["Clethylene has now been finally established as 
via methyne insertion into the C-H bands of methyl groups.88 Organic chemists 
and biochemists are also interested in recoil carbon but as a reagent for the 
production of labelled molecules; e.g. [llC]amino-acids can be produced in small 
yields using recoil "C produced by either 12C(n,2n) or 12C(y,n).89 
Nitrogen.-Attempts to study the mechanisms whereby recoil 13N enters chemical 
combination have shown that such systems (as for recoil C) are very sensitive to 
radiation dose. Thus 13N produced by proton bombardment of water ['"O(p,a)13N] 
gave variable yields of l3No3- and 13NH3 but with nitrate usually in e x c e ~ s . ~ ' ~ The 
reaction [14N(n,2n)13N] in ammonium sulphate solution, however, gave rise to 
mostly reduced products in solution with considerable gaseous activity. la 
Fluorine.-Root and his collaboratorsg0 have made a detailed study of the reactions 
of recoil "F atoms with CH3CF3, the results of which can be summarized as follows: 
84% H"F, 4.2% lsF/F (a), 0.3% 18F/2F (a), <0.2% 18F/2H (a), 5.8% "F/H (b), 
1.0% "F/CH3 (b), 1.3% "F/CF3 (b), where "F/X indicates that 18F replaces X. In 
cases (a) about 80% of the products decompose after the reaction, for ( b ) only about 
27%. Attempts have also been made to develop a so called 'steady-state' model of 
hot-atom chemistry which has been applied to the "F+H2 (with and without Ar) 
P. Volpe and M. Castiglioni, J.C.S. Faraday I, 1978, 74, 818. 
82 N. S. Nogar and L. D. Spicer, J. Chem. Phys., 1977,66,3624; L. J. Ferro and L. D. Spicer, ibid., 1978,69, 
4335; L. D. Spicer, J.C.S. Faraday II, 1978,74,527; M. B. Callahan and L. D. Spicer, J. Phys. Chem., 
1979,83, 1013. 
83 M. Castiglioni and P. Volpe, Radiochem. Radioanalyt. Letters, 1979, 39, 31. 
84 Y. N. Simirskii and L. P. Firsova, Radiokhimiya, 1978, 20, 300. 
85 Y. Aratono, E. Tachikawa, and T. Miyazaki, Radiat. Phys. Chem., 1979,13, 115. 
86 T. E. Boothe and H. J. Ache, J. Phys. Chem., 1979,83,457. 
87 H. Kudo, K. Tanaka, and H. Amano, J. Inorg. Nuclear Chem., 1978,40,363. 
88 K. K. Taylor, H. J. Ache, and A. P. Wolf, J. Phys. Chem., 1978, 82, 2385. 
89 C. N. M. Bakker and F. M. Kaspersen, Radiochem. Radioanalyt. Letters, 1979,39, 1. 
90 R. G. Manning, S.-H. Mo, and J. W. Root, J. Chem. Phys., 1977, 67, 636. 
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Radiochemistry 255 
system." Other systems in which the chemistry of 18F* has been studied experi- 
mentally are with CCIF, {using ['9F(p,pn)18F]: both CF318F and CC1F,l8F were 
found}'* and, in the liquid phase, with substituted benzenes. The ability of recoil 18F 
to replace both C1 and F has also been shown for other chlorofluoromethanes, for 
CC14, and for SF6.93 
Silicon.-Gaspar has continued his investigation of recoil Si atom chemistry utilizing 
the [31P(n,p)31Si] reaction.95 Although the intermediacy of 31SiH2 in the formation of 
["Sil- 1 -silacyclopent-3-ene from irradiated phosphine-butadiene mixtures is an 
attractive hypothesis, detailed studies have thrown doubt on this mechanism. 
Phosphorus.-Neutron irradiation of phosphoric acid or phosphates leads to the 
formation of labelled polymeric but if recoil phosphorus is formed 
[35Cl(n*,~)32P] in the presence of ethanol reduced species P"' and P' are found.97 
Electrophoresis can be used to determine the valency of radioactive phosphorus 
compounds.98 
Su1hpur.-Recoil sulphur can be generated in potassium chloride by [35Cl(n,p)35S]. 
Upon dissolution the radioactive sulphur is found in a variety of valence states, but 
possibly as much as 60% is present as thi~sulphate.~' If the KC1 lattice is doped with 
silver ions the amount of sulphide is decreased whereas SKv: Sv' is unaffected.lo0 
Chlorine.-Interest in the chemistry of recoil chlorine atoms has developed rapidly 
during the past few years and almost all aspects have been the subject of recent work. 
The simplest isotope to study is 38Cl made by 37Cl(n,y). y-Ray emission may be a 
single or multiple process and the average recoil energy is 294 eV.'" True 'hot-atom' 
reactions in the gas phase, such a prominent feature of tritium chemistry, are much 
less common for recoil chlorine atoms, but are nonetheless interesting for all that. 
The simplest reaction, with dihydrogen, has given rise to curious isotope effects when 
yields of 'H38C1 and 2H38CI are compared as a function of CF2C12 moderator 
pressure.lo2 With freons it was found that recoil chlorine atoms could replace 
chlorine atoms about five times as efficiently as fluorine atoms.lo3 Studies of the 
stereochemistry of the chlorine for chlorine replacement reaction have shown that 
whereas retention of configuration is observed for molecules such as (ClFHC), and 
[CIH(CH3)CI2 in the liquid phaselo4the stereochemical course of the reaction can be 
91 K. D. Knierim and J. W. Root, Radiochim. Acta, 1977,24, 103; E. R. Grant, K. D. Knierim, and J. W. 
92 G . A . Brinkman and J. Visser, Internat. J. App l . Radiation Isotopes, 1979, 30, 517. 
93 A . J. Palmer, J. C. Clark, P. L. Horlock, and P. D. Buckingham, J. Labelled Compounds Radiopharm., 
1979,16, 150. 
94 ( a ) G. A . Brinkman, J . T. Veenboer, J. Visser, and L. Lindner, Radiochim. Acta, 1977,24,161; G. A. 
Brinkman, J. Visser, and L. Lindner, ibid., 1979, 26, 77; ( b ) K. D. Van der Linde, S. Spoelstra-Van 
Balen, F. M. Kaspersen, P. W. F. Louwrier, and L. Lindner, ibid., 1977, 24, 167. 
Root, Chem. Phys. Letters, 1978, 53, 588. 
95 R.-J. Hwang and P. P. Gaspar, J. Amer. Chem. SOC., 1978,100,6626. 
96 T. Nakamura, T. Yano, T. Fukuda, and S. Ohashi, Mem. Fac. Sci. Kyushu Univ. Ser. C, 1979, 11, 189. 
97 G . W. A . Newton, V. J. Robinson, and D. K. Sharma, Radiochim. Acta, 1979,26,29, 33. 
98 0. Z. Jovanovic-Kovacevic, Chromatog. Symp. Ser., 1979,1,233. 
99 E. Shikata and T. Kase, Radioisotopes, 1978, 27,229. 
loo M. Kasrai, B. Nabardi, and R. M. Raie, J.C.S. Faraday I, 1978, 74, 2452. 
lo' L. J. Ferro and L. D. Spicer, J. Chem. Phys., 1978,69, 1320. 
'03 F. S. C. Lee and F. S. Rowland, J. Phys. Chem., 1977,81,684, 1222, 1229, 1235. 
' 04 T. R. Acciani, Y.-Y. Su, H. J. Ache, and E. P. Rack, J. Phys. Chem., 1977,82, 975. 
D. J. Stevens and L. D. Spicer, 1 Phys. Chem., 1978, 82, 627. 
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256 D. S. Urch 
altered by changes in solvent polarity (and structure). In the gas phase no such effects 
can occur, yet inversion has been observed in (CH3)HClCCOCl (1) where the space 
c1 
opposite the C1-C bond is very open.'05 Inversion is reduced when groups more 
bulky than methyl are present. This remarkable observation is the first demon- 
stration of a hot-atom replacement reaction proceeding with inversion at a chiral 
centre. cis-trans Isomerization, induced by the recoil chlorine substitution reaction 
in cis- (CF3)CIC=CCl(CF3),106 is, of course, much more understandable. 
Much higher yields of chlorine-labelled molecules are observed in the liquid than 
in the gas phase, presumably due to solvent cage effects, but there is also strong 
evidence now, in aromatic systems, for the existence of a special mechanism for the 
formation of labelled molecules which probably involves some sort of long-lived 
r-complex. lo7 A wide range of halogenobenzenes has now been investigated,"* 
using 34mCl from [35Cl(n,2n)] as well as 38Cl.'09 The chemistry of thermal chlorine 
atoms with unsaturated hydrocarbons can be conveniently studied using recoil 
chlorine by allowing the 'hot' atoms to be moderated by an excess of inert bath gas.lo3 
In the solid state it is found that the yields of labelled compounds in perchlorates and 
u -chlorobenzoic acid are increased upon annealing.' lo 
First-row Transition Metals.-The Szilard-Chalmers reaction has been studied in 
dichlorotitanocene and its derivatives. The chemistry of recoil chromium in solid 
chromates continues to attract considerable attention. The yields of Cr042-, 
[Cr(H20)6]3' 'Cr"'-dimer', and 'Cr"'-polymer' were found to be independent of the 
isotope of Cr (48,49, or 51) produced in the (y,xn) reaction."* Thermal annealing 
and y-irradiation can often cause variations in the yields of labelled species but these 
effects can be studied in isolation using crystals of potassium iodate'13 or ammonium 
chromate114 doped with 51Crrr1. In the case of tris-(8-hydroxy- 
quinolate)chromium(III) maxima in the annealing curves were ascribed to complex 
decomposition. '15 In ferrocene [54Fe(y,2n)52Fe] gives quite high yields of labelled 
starting material, but these yields are very dependent on the polarity of the 
A. P. Wolf, P. Scheuler, R. P. Pettijohn, Kar Chun-To, and E. P. Rack, J. Phys. Chem., 1979,83,1237. 
D. J. Stevens and L. D. Spicer, J. Amer. Chem. Soc., 1978,100,3295. 
lo' S. S. Kontis, D. J. Malcolme-Lawes, and D. S. Urch, Radiochim. Acta, 1977,24, 87. 
lo* H. H. Coenen, H. J. Machulla, and G. Stocklin, J. Amer. Chem. Soc., 1977,99,2892. 
'09 G. A. Brinkman, J. T. Veenboer, J. Visser, F. M. Kaspersen, and L. Lindner, Radiochim. A d a , 1979,26, 
' lo H. J. Arnikar, S. K. Patnaik, and T. P. S. Pathak, Indian J. Chem., 1979, 17A, 226. 
11' M. Hillman and A. Weiss, J. Inorg. Nuclear Chem., 1977, 39, 1921. 
11' T. Kikuchi, T. Ohmori, and T. Shiokawa, Kakuriken Kenkyu Hokoku, 1977, 10, 281; T. Ohmori, T. 
l'' M. I. Stamouli, Radiochim. Acta, 1979, 26, 37. 
'14 M. I. Stamouli, Radiochim. Acta, 1976, 23, 173. 
85. 
Kikuchi, and T. Shiokawa, Radiochem. Radioanalyt. Letters, 1979,37, 233. 
C. 0. B. M. Pinto, J. D. Fabris, G. Duplatre, and R. M. Machado, Radiochem. Radioanalyt. Letters, 
1979, 38, 269. 
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Radiochemistry 257 
solvent.' l6 Very similar chemical effects were observed in a variety of compounds for 
57 Fe and 6oCo produced by electron-capture decay [57Co(EC,X-rays)57Fe] and 
[59Co(n,y)60Co] respectively, supporting the reasonable assumption that species 
similar in charge and translational energy were produced in both cases.'17 Annealing 
studies of the fate of recoil cobalt [59Co(n,y)60m~gCo,"8'"9 59 co (y,n)' 8m*gC~, ' ' ' 
58Ni(y,p)57Co, 57Ni(p - d e ~ a y ) ~ ~ C o ] , ' ~ ~ nickel, and copper atoms'20 in ethyl- 
enediamine,'18 6-diketo,"' and tetraphenylporphine'20 complexes have been made. 
These investigations often reveal many discrete steps in the annealing process, 
probably reflecting recoil atoms that have been trapped in different lattice sites. 
Stereochemical effects also appear to be important. 
Arsenic and Selenium.-y-Irradiation appears to induce annealing in both neutron- 
irradiated arsenates12' and selenates,122 causing increased 'retention' (i.e. labelling of 
the original compounds). Kinetic studies of annealing on these and doped'23 (A13', 
In3', Ca") systems have also been made. The resonance decay 8'mSe(y)81Se induces 
some reduction of selenate(v1) in 
Bromine.-The study of recoil bromine has a long and tortuous history. The decay 
of the isotopes that can easily be made by neutron irradiation of natural bromine is 
complex and the occurrence of relatively long-lived metastable intermediate nucleii 
has given rise to considerable confusion in the interpretation of results. The position 
has been clarified by studies of the chemistry of bromine species produced by 
isomeric transitions (IT), i.e. 80mBr(y)80Br and 82mBr(y)82Br. The metastable nuclei 
have been incorporated into HBr and Br2 and the reactions of the 800r82Br ions 
studied in both gases such as methane,'25v126 some halogenated me thane^,^^^ and 
halogeno-benzenes.'28 It is found that the reactions of Br"+, from the Auger cascade 
induced decomposition of R80782mBr following y-emission, are due solely to its 
charge when R=H but to both charge and kinetic energy when R = Br (a simple 
conservation of momentum effect). In the former case complex ions such as ChBr ' 
(ref. 125) and C6HsXBr' (X = C1, Br, or I)'28 are postulated. By careful analytical 
technique it is possible to separate the chemical reactions that arise from bromine 
activated by either the (n,y) or the (IT) processes. With ethane12' and with methyl 
br~rnide'~' quite similar yields of labelled products (from CH3Br labelled CH3Br > 
L. Lindner and J. C. Kapteyn, Radiochim. Acta, 1979, 26, 97. 
'17 H. Sano, M. Harada, and K. Endo, Proceedings of the International Conference on Mossbauer 
Spectroscopy, 1977,1, 89, ed. D. Barb and D. Torina, Pub. Documentation OfficeCent. Inst. Phys., 
Bucharest, Romania; Bull Chem. SOC. Japan, 1978,51, 2583. 
'18 J. L. Bonte and D. S. Martin, J. Znorg. Nuclear Chem., 1977,39, 1481. 
T. Akimoto, T. Ohmori, and T. Shiokawa, Radiochem. Radioanalyt. Letters, 1978, 36,21. 
120 N. Ikeda, H. Soji, Y. Sakai, and S. Nakajima, Kakuriken Kenkyu Hokoku, 1976,9,177; N. Ikeda, Y. 
Sakai, and H. Shoji, ibid., 1977, 10, 111. 
12' V. G. Dedgaonkar and M. S. Barve, Radiochim. Acta, 1977,24,117. 
122 G . Duplatre, J. Inorg. Znorg. Nuclear Chem., 1978, 40, 1839. 
123 F. M. F. De Jesus, R. M. Machado, and G. Duplatre, Radiochim. Acta, 1979,26,41. 
124 R. Lopez, S. Bulbulian, and J. P. Adloff, Radiochem. Radioanalyt. Letters, 1979, 38, 143. 
12' E. Yagi and K. Kondo, Kakuriken Kenkyu Hohoku, 1976,9,150; K. Kondo and M. Yagi, Bull. Chem. 
126 K. Kondo and M. Yagi, Bull. Chem. SOC. Japan, 1978,51,1284. 
127 M. Yagi and K. Kondo, Kakuriken Kenkyu Hokoku, 1977,10,120. 
12' K. Kondo and M. Yagi, Kakuriken Kenkyu Hokoku, 1978,11,229. 
129 A. Loventhal, M. E. Berg, and E. P. Rack, Radiochim. Acta, 1977,24,91. 
I3O M. E. Berg, W. M. Graner, R. W. Helton, and E. P. Rack, J. Phys. Chem., 1975,79, 1327. 
SOC. Japan, 1978,51, 372. 
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258 D. S. Urch 
CH2Br2 > CHBr3) are observed in the gas phase but of course in these reactor studies 
the chemical form of the molecule in which the resonance transition took place is not 
known. In both cases yields of labelled organic compounds increase with pressure. 
Comparison of (n, y) and (IT) processes have also been made for bromo-benzene~.'~' 
The effect of the 8omBr(y)80Br process has been studied in potassium b r ~ m a t e ' ~ ~ as 
has recoil 78Br made by the (n,2n) r e a ~ t i 0 n . l ~ ~ Annealing studies on reactor- 
irradiated NaBr04 have also been reported. 134 
Krypton.-Oxygen compounds of krypton (KrO,'-??) (carried in tracer amounts by 
sodium xenate in solution), are produced by proton bombardment of sodium 
perbromate 80*82Br(p,~)74*76*77*79 Kr. Of these isotopes 74Kr and to a lesser extent 
Molybdenum.-High retentions of molybdenum activity (990r "'Mo) have been 
observed for a variety of carboxy-, acetylacetonato-, and carbonyl complexes of 
molybdenum. 136 
Indium.-The chemistry and kinetics of recoil indium atoms made by 
["51n(y,y')115mIn] in indium edta complexes have been 
Iodine.-Iodine has a large number of radioactive isotopes whose recoil chemistry is 
being actively investigated. The most studied is, of course, 1281 because of the ease 
with which it can be made by 1271(n,y). Apart from the remarkable reaction with 
methane (more than 50% of the 1281 is found in methyl iodide and other organic 
yields of labelled compounds from reactions with paraffins in the gas 
phase are usually quite small. These yields, as with ethene,139 do increase with 
pressure and in condensed phases (a theoretical Much of the gas-phase 
chemistry of recoil iodine can be understood if account is taken not only of the atom's 
translational energy but also of ionized and electronically excited (charged and 
neutral) species. With unsaturated compounds (e.g. butenes14') a wide range of 
labelled products is formed with methyl iodide sometimes being observed in very 
high yield (-50% total 1281 activity). However, no consistent mechanism can be 
discerned and it is to be hoped that the pattern of labelled products has not been 
disturbed by radiation effects or radiation-induced exchange. Acetylenes have also 
been investigated experimentally140b and again quite high yields of labelled 
compounds have been found, although without any clear indication of the nature of 
the recoil reactions. The reactions of 1281 with chlorobenzenes in various solvents 
Kr are the ones found in chemical combination (30% and -5'/0).~~' 76 
'" H. J. Arnikar, S. K. Patnaik, andT. P. S. Pathak, Radiochim. Acra, 1976, 23, 167. 
''* G. J. Serrano, INISAtomindex, 1978,9, No. 401 016. 
133 J. Kliman, V. Kliment, and S. Mungyer, Radiochem. Radioanalyt. Letters, 1978, 34, 355. 
134 V. V. Gavrilov and V. K. Isupov, Radiokhimiya, 1978, 20, 312. 
13' V. V. Gavrilov, V. I. Tikhonov, and V. K. Isupov, Radiokhimiya, 1978, 20, 627. 
136 L. A. Fucagauchi de Crowley, R. 0. Lara, S. S. Millan, and A. G. Maddock, Radiochim. Acta, 1979,26, 
13' K. Yoshihara, A. Fujita, and T. Shiokawa, J. Inorg. Nuclear Chem., 1977,39,2111; Kakuriken Kenkyu 
''13 E. P. Rack and A. A. Gordus, J. Chem. Phys., 1961,34, 1855. 
139 M. E. Berg, A. Loventhal, D. J. Adelman, W. M. Graner, and E. P. Rack, J. Phys. Chem., 1977,81,837. 
140 ( a ) S. K. Garmestani and E. P. Rack, J. Phys. Chem., 1979, 83, 2316; S. K. Garrnestani, M. L. 
Firouzbakht, and E. P. Rack, ibid., p. 2827; ( b ) M. E. Berg, K.-C. To, and E. P. Rack, Radiochim. Acra, 
1977, 24, 37. 
39. 
Hokoku, 1976,9,193. 
14' K.-C. To, M. E. Berg, and E. P. Rack, J. Phys. Chem., 1977,81, 1239; 1978,82,761. 
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Radiochemistry 259 
have been A wide variety of neutron-rich iodine isotopes is formed 
during uranium fission, and usually found as about one-third iodate and two-thirds 
iodide in In solid magnesium iodate, however, half of the (n, y)-produced 
1281 is found as iodate, and this proportion can be greatly increased on annea1i11g.l~~ 
Lanthanides.-The chemistry of recoil lanthanide atoms 132La, 132,135Ce, 138Pr, and 
139Nd (made by 660MeV proton bombardment of Nd and Pr targets) has been 
shown to depend upon the recoil energy in tri- or hexa-fluoroacetylacetonate 
Recoil techniques can also be used to make complexes of 
promethium.145 
Thallium.-In the mixed-valence compound T113T111'C16, recoil 2"T1 atoms produced 
by the (n,y) reaction are found preferentially to occupy univalent sites (Tl' : TlII' = 
5 : l ) . This ratio is only altered by thermal annealing and then only at those 
temperatures which independent tracer studies have shown to introduce valence 
randomization. 146 
4 Other Radiochemical Topics 
Labelling.-Whilst tritium atoms can be produced in a reactive state either by the 
nuclear transformations in which they are made [e.g. 6Li(n,a)3H] or by the decay of 
an adjacent atom (e.g. 3H2 + 3H3He' + p ) energy can also be imparted by purely 
conventional means such as decomposition of tritium gas on a heated tungsten 
filament. Translationally excited atoms made in this way can be used very success- 
fully to label a wide variety of compounds (usually frozen at 77 K), e.g. halogeno- 
benzenes,84 a m i n o - a ~ i d s , ~ ~ ~ and pharmaceutical materials.148 Bromine labelling 
(82Br) of similar organic compounds (e.g. tyrosine, 2-deoxyuridine, aromatics) can be 
achieved by adding neutron-irradiated potassium bromate to a solution of the 
compound in dilute sulphuric acid: presumably lattice-trapped bromine species are 
the active reagents.149 Methods for trapping 1231 for the subsequent production of 
radiopharmaceuticals using gold foils have been de~cribed'~' and theoretical yields 
of neutron-deficient iodine isotopes 1271(p,m)Xe ( x = 3,5, or 7) have been cal- 
culated. ls l 
Analysis.-y-Ray spectroscopy continues to be the easiest way of identifying and 
measuring specific isotopes. Recent examples of the technique include the deter- 
mination of relative amounts of various plutonium and estimation of the 
14* M. Sharon, J. Univ. Poona Sci. Technol., 1977,50, 37. 
143 K. K. Shrestha, L. Hellwig, and C. Keller, J. Inorg. Nuclear Chem., 1978,40, 1835. 
14* I. I. Gromova, Kh. M. Islamova, N. A. Lebedev, and N. G. Zaitseva, Proceedings of the Tihany 
14' M. Sakanoue, Y. Shirota, H. Shimozawa, and K. Yoshihara, Radiochim. Acta,1977,24, 77. 
146 S. F. Valverde and G. Duplatre, Radiochim. Acra, 1977,24,121; V. S . Fernandez and G. Duplatre, INIS 
Atomindex, 1979, 10, No. 447 910; S. F. Valverde, ibid., 1978, 9, No. 354 396. 
14' M. A. Orlova and A. N. Nesrneyanov, Radiokhimiya, 1978,20,787; E. Filatov, E. F. Sirnonov, and V. P. 
Mogil'nikov, Khim. oysok. Energii, 1979, 13, 373. 
14' A. V. Krasnyanskii, N. Yu. Krernlyakova, S. M. Svetlikin, Yu. N. Simirskii, L. P. Firsova, V. Ya. 
Vorob'eva, E. E. Mikhlina, and L. N. Yakhonotov, Radiokhimiya, 1978,20, 309. 
149 Z. B. Alfassi, Trans. Ann. Meeting Isr. Nuclear SOC., 1978, 6, 19C; Radiochim. Acta, 1979, 26, 93. 
F. Helus, H. Sinn, W. Maier-Brost, and U. Sahm, Radiochem. Radioanalyt. Letters, 1978,32, 311. 
D. B. Syme, E. Wood, I. M. Blair, S. Kew, M. Perry, and P. Cooper, Internat. J. Appl . Radiation Isotopes, 
1978,29,29. 
Symposium on Radiation Chemistry, 1976 (publ. 1977), 4,963. 
151 
lS2 M. I. Belen'kii, V. V. Berdikov, B. S. Iokhin, and M. A. Savorov, Radiokhimiya, 1979, 21, 127. 
Pu
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260 D. S. Urch 
202Pb content of lead ~ a m p 1 e s . l ~ ~ In many cases preliminary chemical treatment is 
necessary, e.g. for the determination of 35S (a &emitter) in a variety of 
compounds.154 
Chemical Effects in y- and X-Ray Emission.-Nucleii are supposed to be 
impervious to mere chemical perturbations and reports of changes in half-lives and 
such like associated with chemical changes are therefore always the subject of much 
interest and some scepticism. The mechanism whereby such changes could be 
communicated to the nuclei is presumably via changes in s-electron densities since 
these orbitals have non-zero electron probabilities at the nuclei themselves. It has 
recently been reported'55 that changes in valency of both tin and chromium can be 
correlated (and indeed by this means reactions followed) with small changes in 
intensities of characteristic y rays, viz. 
Sn"-Sn'": 0.2*0.05% intensity change in the 393 keV y of l131n daughter of '13Sn 
Cr"'-Cr"': 0.10*0.05°/~ intensity change in the 320 keV y of "V daughter of "Cr 
Changes in energies and relative intensities of the X-rays emitted following electron 
capture are perhaps a little easier to anticipate since chemical effects in X-ray 
emission spectra are well known.156 Such changes, if well characterized, would form 
an ideal method for investigating the exact nature of the final site of a recoil atom in 
the solid state. Apart from Mossbauer spectroscopy, which can only be applied to a 
few atoms, there is no method for studying the chemical environment of a recoil atom 
in a solid lattice directly; such information must be inferred from subsequent 
reactions when the solid is dissolved and from annealing work. Unfortunately recent 
work in this embryonic field has concentrated on Ka/Kf3 intensity for transition 
ratios, which, since they arise from core transitions, would not be expected 
to show great (if any) chemical effects. Finding no Ka/K/3 intensity difference in Mn 
spectra following 55Fe decay in Fe" and Fe"' is not surprising since 
none is observed in the X-ray emission spectra of d" and d 5 systems anyway. It is 
valence band-core transitions which should show useful effects. 
153 T. Y. Toribara and F. R. Gibb, Internat. J. Apgl. Radiation Isotopes, 1978,29, 759. 
154 I. Gacs and S. Dombi, J. Radioanalyt. Chem., 1978,42, 375. 
A. N. Murin, S. 1. Bondarevskii, and V. V. Eremin, Radiokhimiya, 1977,19,879. 
D. S . Urch, in 'Electron Spectroscopy', ed. C. R. Brundle and A. D. Baker, Academic Press, London, 
New York, 1979, Vol. 3, p. 1. 
( a ) E. Lazzarini, F. A. L. Lazzarini, and M. Mandelli-Beltoni, Radiochim. Acta, 1978,25,81; ( b ) G. 
Paic and V. Pecar, Fizika (Zagreb), 1977,9 (Suppl. l), 33. 
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