Impact of Coriolis mixing on a two-quasi-neutron isomer in Gd-164(100) and other N=100 isotones

We report on two complementary delayed gamma-ray spectroscopic studies on Gd-164(64)100. The nucleus is produced via spontaneous fission of Cf-252 sources used in selective experimental setups. An isomeric state at 1095 keV with a half-life of 605 (30) ns is confirmed as well as its decay path toward the ground state band. From comparison to other N = 100 isotones and with calculations based on the axially symmetric-deformed quasiparticle random phase approximation (QRPA) using the up-to-date Gogny interaction a 4(-) spin and parity is proposed for the isomer. The state is interpreted as a two-quasi-neutron excitation in line with available data for others N = 100 isotones. The variation of the lifetime of the isomeric state along the N = 100 isotones is interpreted in terms of Coriolis mixing implemented for the first time within axially symmetric-deformed QRPA microscopic calculations.