Study of low-lying levels in 37Ar

The properties of the first five excited levels in 37 Ar were investigated via the 37 Cl(p,n) 37 Ar reaction at E p = 3.98, 4.17, 4.38, and 4.81 MeV and via the 34 S(α,n) 37 Ar reaction at E α = 8.00, 8.50, and 8.60 MeV. The following excitation energies were obtained: E x = 1409.7 ± 0.4, 1611.5 ± 0.4, 2217.8 ± 0.8, 2491.4 ± 0.8, and 2797.0 ± 0.8 keV. These levels were found to decay almost entirely to the ground state. The angular distribution and the linear polarization of the decay gamma rays of these levels were measured. From these measurements definite spin–parity assignments as well as values of the mixing ratio of the ground state gamma-ray transitions were obtained. These are: E x (J π , δ) = 1612 ([Formula: see text], +0.11 ± 0.02), 2218 ([Formula: see text], 0.0 ± 0.02), 2491 ([Formula: see text]), and 2797 ([Formula: see text], −0.16 ± 0.03 or +8.0 ± 1.5, the value of −0.16 being more probable). The measurements were also consistent with a spin of [Formula: see text] for the 1410 keV level. The results are compared with a recent shell-model calculation and are discussed in the context of the solar neutrino capture rate in 37 Cl.