Mass and Decay of a Highly Neutron-Rich Isotope of Phosphorus: 48-secP35

Abstract

${}_{}{}^{35}{}_{}{}^{}\mathrm{P}$ has been produced via the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}+{}_{}{}^{19}{}_{}{}^{}\mathrm{F}\to {}_{}{}^{35}{}_{}{}^{}\mathrm{P}+2p$ reaction using 42-46-MeV ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ ions, and by the ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}(t,\alpha ){}_{}{}^{35}{}_{}{}^{}\mathrm{P}$ reaction using 3.4-MeV tritons. Identification is made from the observed $\beta$-delayed $\gamma$ ray of 1572.41 ± 0.25 keV. By means of the ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}(d,p\gamma ){}_{}{}^{35}{}_{}{}^{}\mathrm{S}$ reaction, the $\gamma$ ray from the first excited state of ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$ has been measured as 1572.24 ± 0.15 keV, in disagreement with previous measurements. The average of the half-lives for ${}_{}{}^{35}{}_{}{}^{}\mathrm{P}$ as measured by the first two reactions is 48.1 ± 1.4 sec. Upper limits were obtained for $\beta$-ray transitions to other excited states in ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$. No information was obtained on a possible $\beta$ transition to the ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$ ground state. The $\beta$-ray spectrum measured in coincidence with the 1572-keV $\gamma$ ray has an end point of 2337 ± 75 keV, establishing a mass excess of -24 936 ± 75 keV for ${}_{}{}^{35}{}_{}{}^{}\mathrm{P}$. These results are consistent with the expected mass and spin-parity (${\frac{1}{2}}^{+}$) of the ${}_{}{}^{35}{}_{}{}^{}\mathrm{P}$ ground state. Comparison of these results with shell-model calculations is presented.