Natural width and Doppler broadening in the 152 Sm 961 keV γ -ray resonance

Abstract

By moving a 152m Eu 2 O 3 source on the tips of a high-speed rotor, the 961 keV emission spectrum has been swept across the resonance line of a stationary Sm 2 O 3 scatterer. The observed resonance/fluorescence intensity has been compared with a curve calculated by taking into account the Doppler effects due to electron capture and thermal motions but neglecting the effects of natural line widths. At negative rotor speeds, when the emission line scans the low-energy wing of the resonance line, the influence of the natural line width on the resonance/fluorescence intensity has been observed. At positive rotor speeds there is a good agreement with the theoretical calculations; this shows that with a stationary source the thermal broadening is dominant in restoring the resonance whereas the line wing overlap is negligible.