Half-life measurements of the 86.6 keV level in233Pa and 59.6 keV level in237Np

The half-lives of the 86.6 keV level in²³³Pa and the 59.6 keV level in²³⁷Np have been measured. A silicon surface barrier alpha detector and a NaI(Tl) gammadetector were used. The decay time spectrum of alpha-gamma coincidences obtained from a start-stop type of time-to-pulse height converter was recorded on a 2048-channel analyser. Analysis of the data gave the following half-life values: $$begin{gathered} T_{frac{1}{2}} :^{233} Pa (86.6 keV level) = (37.4 pm 0.4) ns hfill T_{frac{1}{2}} :^{237} Np (59.6 keV level) = (66.7 pm 0.7) ns hfill end{gathered}$$ . Using the experimental levelT _1/2's, partial gamma-ray half-lives have been calculated for the 86.6- and the 29.6-keV transitions (from the 86.6 keV level) in²³³Pa and the 59.6- and the 26.36-keV transitions (from the 59.6 keV level) in²³⁷Np. The results are compared with the single particle and the Nilsson estimates.