Measurement and analysis of the excitation function for alpha-induced reactions on Ga and Sb isotopes

Citations Over TimeTop 19% of 1990 papers

Abstract

Excitation functions for the reactions $^{69}\mathrm{Ga}$(\ensuremath{\alpha},xn${)}^{73\mathrm{\ensuremath{-}}x}$As, $^{69}\mathrm{Ga}$(\ensuremath{\alpha},p3n${)}^{69}$Ge, $^{69}\mathrm{Ga}$(\ensuremath{\alpha},2p4n${)}^{67}$Ga, $^{71}\mathrm{Ga}$(\ensuremath{\alpha},xn${)}^{75\mathrm{\ensuremath{-}}x}$As, $^{121}\mathrm{Sb}$(\ensuremath{\alpha},xn${)}^{125\mathrm{\ensuremath{-}}x}$I, $^{121}\mathrm{Sb}$(\ensuremath{\alpha},p3n${)}^{121}$Te, and $^{123}\mathrm{Sb}$(\ensuremath{\alpha},xn${)}^{127\mathrm{\ensuremath{-}}x}$I were obtained from the measurements of the residual activity of stacked foils from threshold to 65 MeV. The excitation functions for the production of $^{74}\mathrm{As}$, $^{72}\mathrm{As}$, $^{71}\mathrm{As}$, $^{69}\mathrm{Ge}$, and $^{67}\mathrm{Ga}$ from \ensuremath{\alpha}-induced reactions on Ga and $^{126}\mathrm{I}$, $^{124}\mathrm{I}$, $^{123}\mathrm{I}$, $^{121}\mathrm{I}$, and $^{121}\mathrm{Te}$ from \ensuremath{\alpha}-induced reactions on Sb are presented.The experimental data are compared with calculations considering equilibrium as well as preequilibrium reaction mechanisms according to the hybrid model of Blann. The high-energy part of the excitation functions are dominated by the preequilibrium reaction mechanism. Calculations were done using the a priori calculational method of Blann. From the reactions $^{71}\mathrm{Ga}$(\ensuremath{\alpha},3n${)}^{72}$As and $^{123}\mathrm{Sb}$(\ensuremath{\alpha},3n${)}^{124}$I, an initial exciton number ${n}_{0}$=4 (${n}_{n}$=2, ${n}_{p}$=2, ${n}_{h}$=0) with the mean-free-path multiplier parameter k set to 2 has been deduced for both the targets. However, there are a few exceptions. The theory overestimates the cross section for the $^{69}\mathrm{Ga}$(\ensuremath{\alpha},2p4n${)}^{67}$Ga reaction whereas it underestimates the cross section for the $^{121}\mathrm{Sb}$(\ensuremath{\alpha},p3n${)}^{121}$Te reaction and the high-energy tail of $^{121}\mathrm{Sb}$(\ensuremath{\alpha},2n${)}^{123}$I excitation function. For the (\ensuremath{\alpha},2p4n) reactions on Ga the discrepancy between theory and experiment may be attributed partly to a breakup of the \ensuremath{\alpha} particle and partly to much more complex reaction mechanisms, whereas for the $^{121}\mathrm{Sb}$(\ensuremath{\alpha},p3n${)}^{121}$Te reaction two different reaction mechanisms may be attributed.The large discrepancy between theory and experiment for the reaction $^{121}\mathrm{Sb}$(\ensuremath{\alpha},2n${)}^{123}$I at the high-energy tail of the excitation function may be attributed to emission of more than one preequilibrium nucleon which the theory cannot account for at present. Barring these reactions we have found that the overall agreement between theory and experiment is reasonably good, taking the limitations of the theory into account.

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