The mass of ${}_{}{}^{33}{}_{}{}^{}\mathrm{Si}$ has been determined by forming this 6.3-sec activity in the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}({}_{}{}^{18}{}_{}{}^{}\mathrm{O},2p+n){}_{}{}^{33}{}_{}{}^{}\mathrm{Si}$ reaction with 50-MeV ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ ions and by measuring the spectrum of $\beta$ rays in coincidence with 1848-keV $\gamma$ rays. An end-point energy of ${3980}_{-200\mathrm{}}^{+250\mathrm{}}$ keV is found for the coincident $\beta$ rays which establishes the mass excess of ${}_{}{}^{33}{}_{}{}^{}\mathrm{Si}$ as ${-20509\mathrm{}}_{-200\mathrm{}}^{+250\mathrm{}}$ keV. This result differs from the previously estimated mass by ${560}_{-200\mathrm{}}^{+250\mathrm{}}$ keV. $\mathrm{Log}\mathrm{ft}$ values for the decay of ${}_{}{}^{33}{}_{}{}^{}\mathrm{Si}$ are presented and compared with shell-model calculations. Several heavy-ion compound reactions which might be used to produce other neutron-rich nuclei in the $s-d$ shell are listed.

• Received 24 April 1972

DOI:https://doi.org/10.1103/PhysRevC.6.825