Investigation of J → J M1 transitions in 38Ar

Abstract

The γ-decay of eight 37Cl(p, γ)38Ar resonances in the range Ep = 1.0–1.8 MeV has been investigated with a 20 cm3 Ge(Li) detector. Precision γ-ray energy measurements yield the energies of 23 bound states of 38Ar (errors 0.14–3.0 keV) and the Q-value of the 37Cl(p, γ)38Ar reaction, Q = 10 242.5±1.1 keV. Mean lifetimes (or lower limits) of 12 bound tates were found from measurements of γ-ray Doppler shifts. The spins and parities of levels at Ex = 4.57, 4.88, 5.51, 6.21, 6.60, 6.67 11.35 and 11.93 MeV have been determined as Jπ = (2−), 3−, 3(−), 4−, 4−, (5−), 3− and 4−, respectively, on the basis of γ-ray angular-distribution and polarization measurements and/or intensity considerations. Several γ-ray multipole mixing ratios were obtained. The strong Jπ = 4− resonance at Ep = 1 732 keV can be regarded as the analogue of the third excited state in 38Cl.

The strength of M1 transitions of J → J character, up to 0.4–0.6 W.u., is an order of magnitude larger than that of J → J±1 transitions.