A Search for Short-Lived Nuclear Isomers

A search for short-lived isomeric transitions has been initiated. Using a delayed coincidence apparatus having an over-all resolution of 2×${10}^{-9\mathrm{}}$ second, sixteen gamma-transitions were investigated for half-lives in the 2×${10}^{-9\mathrm{}}$ to ${10}^{-7\mathrm{}}$ second range. Metastable states in${\mathrm{K}}^{41}$, 1.3 Mev above ground and in ${\mathrm{Ta}}^{181}$, 471 kev above ground were verified, while the remaining transitions were found to have half-lives less than 2×${10}^{-9\mathrm{}}$ second. Weisskopf's formula relating spin change and half-life, together with internal conversion information, were applied to these data, and definite spin changes were assigned to five of the transitions.