Lifetimes of the low-energy M1 transitions in La137 and Kr83

Using conventional time to pulse-height techniques, the lifetimes of the low-lying levels in La137 and Kr83 have been measured, despite the low γ-ray energies (10 and 9.3 keV) and the large internal conversion coefficients (130 and 11). The results of 89±4 and 147±4 nsec, respectively, correspond to retardation factors of 370 and 45 over the single-particle model predictions for those M1 transitions.