Spin determinations of 31P levels from the 30Si(p, γ) reaction

Abstract

The angular distributions of primary and secondary γ-ray transitions at seven resonances in the 30Si(p, γ) 31P reaction were measured with a 30 cm 3 Ge(Li) detector. The strengths of the resonances between 800 and 1000 keV and the strength of the E p = 2187 keV resonance were determined. The mean lifetime τ m (or upper limits) for the 31P 5.53, 5.56 and 5.67 MeV levels was obtained from γ-ray Doppler shift measurements as <37, <25 and 45±20 fs, respectively. The measurements lead to the following J π assignments of 31P bound states and resonance levels: J π(4.63) = 7 2 + ( 5 2 +), J π(5.01) = 3 2 ( 1 2 −), J π(5.02) = 1 2 ( 3 2 +), J π(5.53) = 7 2 ( 5 2 +), J(5.56) = 3 2 , J(5.67) = 5 2 , J(6.40) = 7 2 , J(6.93) = ( 5 2 , 7 2 ), J(8.22) = 7 2 and J π(8.23) = 5 2 − . There are strong arguments which allow to identify the 5.01 and 5.67 MeV levels with the 2 p 3 2 and 1 f 5 2 single-particle states, respectively. The even-parity states in 31P up to 5.8 MeV are compared with recent many-particle shell-model calculations.