High-resolution (e, e') study of isovector M1 and M2 transitions in the oxygen isotopes: (II). 17O

Abstract

In a high-resolution electron scattering experiment, six isospin T = 3 2 levels in the excitation energy region of 11–15.3 MeV were populated in 17O. Five transitions at E x = 11.08, 12.47, 12.99, 14.23 and 14.75 MeV are predominantly of M2 nature with transition strengths B(M2, k)↑ = 6.1 ± 1.9, 6 ± 3, 6 ± 3, 46 ± 7 and 27 ± 9 μ N 2 · fm 2, respectively. The transition to the 15.10 MeV level is mainly M1 with B(M1, k)↑ = 0.14 ± 0.04 μ N 2. For this level, a tentative spin-parity assignment of J π = 3 2 + is possible. Also, a spin assignment of J π = 9 2 − is preferred for the 14.75 MeV level. The comparison of the transition strength to the level at 11.08 MeV with the prediction from the analogous unique first-forbidden β − decay of the 17N ground state indicates that it may be important to include p 3 2 -hole configurations in the ground-state wave function of 17O. A comparison made with the corresponding E1 transitions in 17F, by estimating the possible longitudinal component for the 14.23 MeV transition and assuming that the 12.99 MeV transition is pure E1, shows that mirror asymmetries in the mass 17 pair may be of non-zero magnitudes.