LXIX. The radioactivity of183Ta,185Ta,183mWand185mW

Abstract

The following radiation characteristics of the neutron excess tantalum isotopes ¹⁸³Ta and ¹⁸⁵Ta and of the isomers ^183mW and ¹⁸⁵W have been determined : ¹⁸⁵Ta does not decay to any appreciable extent via the isomer ^185mW and the 175 kev gamma-ray from ¹⁸⁵Ta is not the same as the 165 kev gamma-ray from ^185mW. The 125 kev gamma-ray from ¹⁸⁵Ta and the 130 key gamma-ray from ^185mW are probably the same and due to transition to the ground state of ¹⁸⁵W. Unless there is an undetected rate-determining transition the 165 key gamma-ray from ^185mW is then due to the isomeric transition and from half-life and K conversion considerations it may be classified as E3. Similarly the 155 kev gamma-ray in ^185mW is probably from the rate-determining transition. The classification of the ^185mW isomeric transition type on the basis of K conversion measurements is not unambiguous.