Nuclear Resonance Fluorescence inCe140

Measurements of the lifetime of the 1.6-Mev first excited state of ${\mathrm{Ce}}^{140}$ have been performed using the nuclear resonance fluorescence method. Self-absorption experiments using Ce metal and Ce${\mathrm{O}}_2$ scatterers and absorbers performed at 300°K and at 78°K yield a mean life of (1.10±0.15)×${10}^{-13\mathrm{}}$ second for this state. Formulas are presented for the analysis of resonance fluorescence experiments using thick scatterers and absorbers.