The shape of the Doppler-broadened nuclear resonance fluorescence line

Abstract

Resonance fluorescence from the 279 keV level of Tl 203 was studied using a high speed rotor. The shape of the complete Doppler-broadened resonance fluorescence line was measured by observing resonance scattering at different source velocities. The source velocities were varied from a minimal effect at rest through the maximum resonance effect at 460 m/s until the effect dropped almost to zero again at 930 m/s. It is shown that the ratio of the lifetime of the 279 keV transition calculated from the data in the lower half of the curve to that calculated from the upper part of the curve is 1.02 ± .04. Also, the ratio of the lifetimes computed from the data (using the resonance cross-section formula) to the lifetime calculated from the area under the curve (which is proportional to the integral over the velocity of the resonance cross section) is 1.01 ± .04. As expected, the use of the area under the Doppler-broadened line in the calculation allows nuclear lifetime measurements independent of possible line structure.