Structure of neutron-rich tungsten nuclei and evidence for a 10 - isomer in 190 W

Isomers in the neutron-rich nucleus W-190 have been characterized. A 10(-) state from the 9/2(-)[505] circle times 11/2(+)[615] two-neutron configuration with a 240-mu s lifetime decays via a K-allowed, 97-keV, M2 transition to an 8(+) state with a 160-ns lifetime from the 9/2(-)[505] circle times 7/2(-) [503] neutron configuration. New states have also been identified in W-188, including a K-pi = 8(-), 158-ns isomer from the 9/2(-)[614] circle times 7/2(+)[404] two-proton configuration. The K hindrance is observed to decrease with increasing neutron number, consistent with a trend toward increasing triaxial softness.