Properties of Excited States ofP31. I. Gamma-Ray Spectra and Decay Schemes

Abstract

Gamma-ray decay schemes of the resonances in the reaction ${\mathrm{Si}}^{30}(p, \gamma ){\mathrm{P}}^{31}$ at $E_p=1177, 1204, 1324, 1392, 1400, 1481, 1489, \mathrm{and} 1509$ keV are proposed from a study of pulse-height spectra and coincidence measurements. With some exceptions, the decay properties of intermediate states of ${\mathrm{P}}^{31}$ are found to be in agreement with previously existing information. The exceptions are (1) The 3.51-MeV level appears to decay to either the 1.27- or to the 2.23-MeV level (or both) in addition to the well-known decay to the ground state. (2) The 4.26-MeV level decays to the ground state and to the first excited state with the relative intensities 84% and 16%, respectively. (3) The 5.01-MeV level decays to the first excited state in addition to the previously reported decay to the ground state. Evidence is presented for the decay properties of the 4.63- and 4.78-MeV levels for which there is no previous information. Evidence is presented for the existence of four bound states between 5- and 7-MeV excitation which have not previously been reported. A relatively strong and well isolated transition to the 3.41-MeV level was found at the 1509-keV resonance. This transition is of considerable interest because it can be used to determine the spin and parity of the 3.41-MeV level for which no assignments exist.