As79via proton pickup

Abstract

The reaction $^{80}\mathrm{Se}(\mathrm{t}, \ensuremath{\alpha})^{79}\mathrm{As}$ has been investigated with an 18-MeV triton beam. Twenty-six levels of $^{79}\mathrm{As}$ (many of them previously unreported) have been identified up to about 3.5 MeV excitation energy. Angular distributions were measured and compared with distorted-wave Born-approximation calculations, in order to extract $L$ values and spectroscopic factors. Most of the expected strength for pickup from the $2p$ and $1{f}_{\frac{5}{2}}$ orbitals is observed. Behavior of the low-lying negative-parity states for various As isotopes is presented and compared with the predictions of a rotational model with prolate deformation and Coriolis coupling. The observed first and second $\frac{9}{{2}^{+}}$ states in odd-$A$ isotopes give further evidence for the shape transition suggested recently for this mass region.NUCLEAR REACTIONS $^{80}\mathrm{Se}(\mathrm{t}, \ensuremath{\alpha})^{79}\mathrm{As}$, $E=18$ MeV; measured $\ensuremath{\sigma}({E}_{\ensuremath{\alpha}}, \ensuremath{\vartheta})$. $^{79}\mathrm{As}$ deduced levels, $L$, $\ensuremath{\pi}$, ($J$), spectroscopic factors. DWBA analysis, enriched target.