Energy Levels ofAs75

Abstract

The excited levels of ${\mathrm{As}}^{75}$ were investigated by studying the decay schemes of ${\mathrm{Se}}^{75}$ and ${\mathrm{Ge}}^{75}$. Beta- and gamma-ray energies, internal conversion coefficients and relative transition intensities were measured. In addition, coincidence and gamma-gamma directional correlation experiments were performed. ${\mathrm{Se}}^{75}$ electron-captures to a level at 402 kev in ${\mathrm{As}}^{75}$; eleven transitions of indicated energy and multipolarity follow the electron-capture process: 25, $66(M1+E2\mathrm{})\mathrm{}$, 81, $97\left(E2\mathrm{}\right)\mathrm{}$, $121(M1+E2\mathrm{})\mathrm{}$, $136(M1+E2\mathrm{})\mathrm{}$, $199(M1+E2\mathrm{})\mathrm{}$, $265(M1+E2\mathrm{})\mathrm{}$, $280\left(E2\mathrm{}\right)\mathrm{}$, 305, and $402\left(M1\mathrm{}\right)\mathrm{}$ kev. ${\mathrm{Ge}}^{75}$ decays by emission of negative beta groups with endpoint energies of 1.19, 0.98, 0.92, 0.72, and 0.55 Mev. Subsequently, six gamma rays with the following energies are emitted: 66, 199, 265, 427, 477, and 628 kev. A level scheme for ${\mathrm{As}}^{75}$ is proposed and plausible spin and parity assignments are discussed. The evidence indicates that most of the levels of ${\mathrm{As}}^{75}$ have spin ½ or $\frac{3}{2}$ and are not single-particle shell-model states.