Specific radiation and recoil energy effects in recoil implantation reaction of51Cr in metal acetylacetonates

In recoil implantation reaction of⁵¹Cr in Cr/acac/₃ a polymer component which was sensitive to radiation dose was found. However, a retention type component⁵¹Cr/acac/₃ was not so sensitive to radiation dose. A remarkable dependence of the yield of⁵¹Cr/acac/₃ on recoil energy was found in the range 10²–10⁶ eV in recoil implantation using a thin film technique. This suggests a special role of implantation reaction in solids.     

Mechanism of recoil implantation reactions of technetium and ruthenium in metal acetylacetonates

Recoil implantation of Tc and Ru in metal acetylacetonates were performed using ruthenium metal as a source and M^III/acac/₃ and M^II/acac/₂ complexes as catchers. The recoil atoms were obtained by¹⁰⁰Ru/, p/^99mTc and⁹⁸Ru/, n/⁹⁷Ru reactions. The yields of Tc/acac/₃ and Ru/acac/₃ were clearly dependent on the force constant of the bond between the central metal atom and oxygen in acetylacetone K/M–O/. A plot of the yield vs. 1/K(M–O) showed a linear relationship. However, the yield of Tc/acac/₂ implanted in M/acac/₂ did not show such a dependence on the force constant. The difference of the mechanism of complex formation between Tc/acac/₃ and Tc/acac/₂ was discussed on the basis of a reaction cage surrounding the recoil atom and of reaction time necessary for competition between the recoil atom and the central metal of the catcher complex.     

Hot atom chemistry in oxyanion targets. Part IV1: Recoil isochronal annealing in permanganates

Investigations on isochronal annealing behaviour of /n, / activated⁵⁶Mn recoils in crystalline potassium and ammonium permanganates have given different results indicating a varying degree of sensitivity of the samples to recoil annealing. The presence of ammonium ion in ammonium permanganate shows the reduction of recoil species during annealing. Vand-Primak model has been utilized to deduce the kinetic behaviour by which the energy of activation is found to be 1.1 and 1.2 eV for KMnO₄ and NH₄MnO₄, respectively. Furthermore, the present work reveals the role of defects in the transient reactions of the lattice stable precursors and hence the mechanism of the recoil reactions.     

A new approach to the study of normalized appearance energy of hot atom reaction product in optical isomers of tris/acetylacetonato/ruthenium/III/

Appearance energy is originally the threshold energy at which récoil products begin to be observed. This was determined by /, '/ reactions. Afterwards, an alternative technique has been developed to determine it by summing up recoil energy spectrum. The latter technique assumed a step function rising at energy E_O in the yield-energy relation. E_O should be defined as normalized appearance energy /NAE/, because it is not threshold energy in its original sense. The NAE for isomerization from to /or reverse/ in Ru/acac/₃ was estimated to be 29 eV, and that for free atom /or ion/ formation was calculated to be 34 eV. The 5 eV difference seems to indicate an energy interval in which isomerization effectively occurs in the recoil reaction.     

Reactions of recoil tritium generated by the3He/n,p/3H reaction with aromatic compounds-intramolecular tritium distribution and radiochemical yield

Reactions of recoil tritium with benzoic acid, acetanilide and -phenethyl alcohol were studied using the³He/n,p/³H reaction. The tritium distribution in the aromatic ring is approximately uniform in all the irradiated compounds and the tritium activity per C–H bond in the methyl and ethylene groups is 7 to 8 relative to that of the corresponding ring as standard /=100/. These findings are substantially the same as those obtained previously by the⁶Li/n,/³H reactions, suggesting the same mechanism of tritiation for both recoil reactions. The tritiated parent compounds were obtained in high radiochemical yields; 45% for benzoic acid, 30% for acetanilide, 12% for -phenethyl alcohol.     

Recoil reactions of38Cl and128I in some heterocyclic systems

Halogen recoil following /n, / reaction has been studied in some heterocyclic systems. The organic yields are 60% for irradiation as solids: exceptions are dioxanide furoate /34%/ and 5-chloro isatoic anhydride /31%/. As solutions in 11 THF + benzene and 11 HTF+DMSO, these yields are lower by 10% and decrase further when only THF is the solvent. Mass-spectroscopy data revealed the possible fragmentation pattern.     

Self-irradiation effects in plutonium compounds and the role of thermal spikes: EPR studies

The self-irradiation effects caused by -radiation in a number of plutonium compounds have been studied using EPR technique. The radical species formed have been identified and the spin concentration measurements have been made. The efficiency parameter , and the radiation-chemical G-value have been determined. The observed and G-values are interpreted on the basis of thermal spike phenomena associated with -paricles and recoil nuclei in the solid phase.     

The recoil reaction of technetium in mer- and fac-tris/benzoylacetonato/ruthenium/III/

The recoil reactions of technetium produced by¹⁰⁰Ru/γ, p/^99mTc reaction were studied in γ-irradiated mer- and fac-Ru/ba/₃ targets. Yields of mer- and fac-Tc/ba/₃ were determined by column chromatographic separation developed in our previous work. In the initial recoil reaction yields mer-form of Tc/ba/₃ was much more abundant than fac-form in the mer-Ru/ba/₃, but the reverse held good in the fac-Ru/ba/₃ showing selectivity in recoil replacement reactions in geometrical isomers. In the annealing reactions, however, such selectivity disappeared and the fac/mer ratio for the annealed portions could be explained by the following mixed mechanisms of ligand incorporation. $$\begin{gathered} Tc/ba/_2^ + + ba^ - \to Tc/ba/_3 \hfill \\ Tc/ba/^{2 + } orTc^{3 + } + xba \to Tc/ba/_3 \hfill \\ /x = 2or3/. \hfill \\ \end{gathered} $$      

An old-new tool for nuclear analysis: Time-of-Flight spectrometry

The Time-of-Flight (ToF) technique can be used for mass identification, for separation of a specified mass or for measuring the energy of a given mass particle. The instrumentation required is simple and low in cost. The method features high yield, transmission efficiency is typically of 5 to 20%. Even with short flight paths (5 to 10 cm), ToF has adequate mass resolution (M/M300 to 500) for identifying isotopic species. This paper examines the scope of ToF in nuclear science with examples in mass spectrometry, in mass separation and in kinetic energy measurements of fixed mass particles. An example of the latter is the energy determination of recoil nuclei. If a recoil is produced inside a solid, the residual recoil energy reveals the depth from which it originates. This approach is used for profiling nitrogen via¹⁴N(n, p)¹⁴C. The ToF measurement of the¹⁴C recoil energies reveals the depth distribution of nitrogen with better than 50 Å resolution.     

Determination of activation energies in the annealing of cobalt recoil atoms in single and double complexes

Activation energies for the recombination of point defects generated by the /n,/ reaction in Ba (CoEDTA)₂·4H₂O, t-(Co(en)₂(NO₂)₂)Cl and (Co(en)₂(NO₂)₂) (CoEDTA)·1H₂O, have been evaluated using isothermal step annealing. The reselts were interpreted in terms of compound structures. It is possible to relate the recoil atom behaviour between single complexes and the double one.     

Recoil implantation reaction in geometrical isomers of tris/benzoylacetonato/chromium/III/

Hot atom chemical reaction by⁵⁰Cr/n, /⁵¹Cr and⁵²Cr/, n/⁵¹Cr reactions, and recoil implantation reaction by⁵¹V/p, n/⁵¹Cr reaction were investigated using geometrical isomers /mer and fac/ of tris/benzoylacetonato/ chromium/III/ /Cr/ba/₃/. The production of counter isomer was observed for both mer- and fac-targets, although the yield of labelled parent isomer was larger. The observed mer/fac yield ratio suggests that the main formation mechanism of⁵¹Cr/ba/₃ is the reaction of ba^– and Cr/ba/ ₂ ⁺ which has the same geometrical configuration of target complex, and the substitution reaction of central metal atom by recoil⁵¹Cr. Furthermore, implantation gave rise to a much higher yield of labelled Cr/ba/₃ compared to the case of in situ nuclear recoils.     

Determination of pre-scission kinetic energy in low energy fission using isotonic charge distribution model

The spectral lines of the 478 keV prompt -ray from^7*Li produced in the¹⁰B(n, )^7*Li reaction were measured for a silicon wafer coated with a thin boron layer using neutron beams. The shapes of the Doppler broadened lines were found to depend greatly on the angle between the measurement axis and the boron layer surface. The angular dependence was interpreted according to whether the energetic^7*Li ions are ejected into air or into the substance in the forward or backward recoil of^7*Li to the -ray detector.     

Determination of carbon in thin layers by means of the12C(d,n)13N nuclear reaction using a 2 MeV Van de Graaf accelerator

A nondestructive method for carbon determination in layers of 3–10 m thickness is considered. The method is based on using the¹²C(d, n)¹³N nuclear reaction with simultaneous account of surface contamination by means of the¹²C(d, p)¹³C competitive reaction. The total cross sections for the¹²C(d, n)¹³N reaction were measured from 0.4 to 1.7 MeV. Proton beam annealing was applied with the purpose of lowering surface carbon content. The detection limit of carbon by this method is 0.5 ppm, relative standard deviation is 0.06. Disturbing effects of carbon diffusion and¹³N recoil backs cattering are also taken into account.     

Characterisation of lead rhodizonate as barium and radium adsorber from fresh water

A series of metal -diketonates were irradiated with bremsstrahlung of maximum energy of 50 MeV and the recoil behavior of⁷Be, formed from¹²C of ligands through¹²C(, n)⁷Be reaction, was investigated.⁷Be nuclides thus formed were detected partially as central metal atoms of the complexes. Complex yields of⁷Be were compared and an anomalously high yield was observed in tris-acetylacetonatocobalt(III) [Co(acac)₃].     

Mechanisms of chemical reaction initiated by recoil implantation

Mechanisms of chemical reactions initiated by recoil implantation were studied in the systems⁵¹Cr+M/acac/₃⁵¹Cr/acac/₃ where M is a trivalent metal. The yield of⁵¹Cr/acac/₃ increased linearly with an increase of inverse of the force constant of metal-oxygen bonding K(M–O). This indicates that there is competition between the implanted⁵¹Cr atom and M. However, exception for this trend was the case of Co/acac/₃ catcher, for which the yield of⁵¹Cr/acac/₃ was much higher than that expected for a competition reaction. Complex features of the replacement reaction caused by implantation are discussed in this system.     

Recoil behaviour of central metal atoms in cobalt and zinc phthalocyanine mixed crystals

The retentions of cobalt, copper and zinc recoils were studied in the mixed crystal system of -cobalt phthalocyanine and -zinc phthalocyanine. It was suggested that a part of the retentions of cobalt and zinc recoils was due to a competitive process. The relationship between the retentions of the zinc recoils and their recoil energy in different matrices was discussed.     

Hydrogen analysis by elastic recoil spectrometry: A new approach for absolute quantitative measurement

We have developed an absolute, quantitative procedure to determine the hydrogen content and to describe its concentration profile in the near-surface region of solids. The experimental technique used is the Elastic Recoil Detection Analysis of protons induced by helium-4 beam bombardment in the energy range 1.8 MeV. The deconvolution of the recoil spectra is obtained by means of a computer program which simulates all the physical processes of⁴He/¹H interaction. The hydrogen content is calculated using a new recoil cross section expression. The analyses are performed in silicon crystals implanted with hydrogen at 10 keV. The implantation dose is evaluated with an accuracy of 10% and the hydrogen depth profile is given with an accuracy of ±10 nm around 200 nm.     

Column chromatography of carrier-free Tc/III,IV/-TTA complexes

The chemical species of carrier-free technetium, which were extractable into a TTA-benzene solution on reduction of⁹⁶TcO ₄ ^– either with NaBH₄ or concentrated HCl, were studied by means of silica gel chromatography. Elution peaks ascribed to the formation of Tc/tta/₄ and Tc/tta/₃ type complexes were observed. The latter complex was also synthesized by recoil effect of Ru/, p/Tc reactions in -irradiated Ru/tta/₃.     

Thermal and radiation annealing in131I−-doped periodate crystals

Isothermal annealing at temperatures between 90 and 250°C and radiation annealing at 40, –76 and –196°C were studied in sodium periodate crystals doped by rapid crystallization and by spray techniques. The results showed the occurrence of transfer annealing because the dopant was converted to the oxidized forms of iodate and periodate depending on the treatment conditions. Similarities with the annealing behaviour of recoil species in neutron irradiated periodate systems are established and the Bellido and Wiles stepwise oxidation model is used to explain the mechanism of the processes.     

Hydrogen profile analysis in a-C:H films by elastic recoil detection (ERD)

Summary The measurement of hydrogen profiles in diamond-like carbon films (a-CH) by elastic recoil detection (ERD) and the decrease of the H content after irradiation with Ni ions are described.

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Wasserstoffprofilanalyse in a-C:H-Filmen durch elastische Rückstoß-Detektion (ERD)

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Guest scientist from IMR of Academia Sinica, Shenyang, People's Republic of China