Interactions of He3 Particles with Be9 , C12 , O16 , and F19

Excitation functions for reactions induced by $^{3}\mathrm{He}$ particles in Be, C, O, and F were determined by irradiating thin foils of beryllium, Mylar, Teflon, and nylon with $^{3}\mathrm{He}$ ions of energies from 3 to 10 MeV. The radioactive products were assayed by gamma spectrometry, and their decay curves fitted by least-squares analysis. The maximum cross sections (and corresponding $^{3}\mathrm{He}$ energies) were $^{9}\mathrm{Be}(^{3}\mathrm{He},n)^{11}\mathrm{C}$, 113\ifmmode\pm\else\textpm\fi{}11 mb (4.3 MeV); $^{12}\mathrm{C}(^{3}\mathrm{He},n)^{14}\mathrm{O}$, 16.5\ifmmode\pm\else\textpm\fi{}1.8 mb (6.3 MeV); $^{12}\mathrm{C}(^{3}\mathrm{He},d)^{13}\mathrm{N}$, 98.9\ifmmode\pm\else\textpm\fi{}12.2 mb (9.5 MeV); $^{12}\mathrm{C}(^{3}\mathrm{He},\ensuremath{\alpha})^{11}\mathrm{C}$, 366\ifmmode\pm\else\textpm\fi{}26 mb (8.2 MeV); $^{16}\mathrm{O}(^{3}\mathrm{He},p)^{18}\mathrm{F}$ 436\ifmmode\pm\else\textpm\fi{}44 mb (6.3 MeV); $^{16}\mathrm{O}(^{3}\mathrm{He},\ensuremath{\alpha})^{15}\mathrm{O}$, 169\ifmmode\pm\else\textpm\fi{}17 mb (6.6 MeV); $^{19}\mathrm{F}(^{3}\mathrm{He},\ensuremath{\alpha})^{18}\mathrm{F}$, 22.1\ifmmode\pm\else\textpm\fi{}2.0 mb (7.1 MeV); and $^{19}\mathrm{F}(^{3}\mathrm{He},\ensuremath{\alpha}n)^{17}\mathrm{F}$, 50.4\ifmmode\pm\else\textpm\fi{}5.0 mb (8.2 MeV). Results for some of these reactions, previously obtained by other workers, were in reasonable agreement with our data; in particular, the fine structure of the reaction $^{12}\mathrm{C}(^{3}\mathrm{He},n)^{14}\mathrm{O}$ was confirmed in these experiments. An integral excitation function, calculated from the differential data of Towle and Macefield for the $^{9}\mathrm{Be}(^{3}\mathrm{He},n)^{11}\mathrm{C}$ reaction, agreed with the integral data obtained in this work. The distorted-wave theory of direct reactions was used to compute excitation functions for comparison with integral data for $^{3}\mathrm{He},\ensuremath{\alpha}$ reactions on $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, and $^{19}\mathrm{F}$, and for the ($^{3}\mathrm{He},d$) reaction on $^{12}\mathrm{C}$. The results of the comparison between theory and experiment indicate that a direct mechanism is operative in all the cases studied, except the $^{12}\mathrm{C}(^{3}\mathrm{He},\ensuremath{\alpha})^{11}\mathrm{C}$ reaction, which appears to proceed to a large extent by way of a compound-nucleus reaction. Thus, the integral data indicate that the primary mechanisms operative in the reactions ($^{3}\mathrm{He},\ensuremath{\alpha}$) on $^{16}\mathrm{O}$ and $^{19}\mathrm{F}$, and ($^{3}\mathrm{He},d$) on $^{12}\mathrm{C}$, are respectively direct pickup and stripping.