Precise determination of hyperfine interactions and second-order doppler shift in 149Sm Mössbauer transition

Abstract

We have succeeded in precisely determining the hyperfine interactions, particularly the isomer shifts, in the 149Sm Mossbauer transition. The difference in the nuclear radii between the ground and excited states is critical for the determination of isomer shifts but is relatively small in 149Sm. Therefore, the precise determination by 149Sm Mossbauer spectroscopy is difficult. The recent development of synchrotron-radiation-based Mossbauer spectroscopy allows the isomer shifts to be determined more precisely than previously with the help of wellcollimated synchrotron radiation. In particular, the time-window effect assists the precise determination of hyperfine interactions in the 149Sm Mossbauer transition because this effect enables us to measure spectra with higher energy resolution than natural linewidth determined by the lifetime of the excited states. Meanwhile, highenergy-resolution measurements to determine center shifts by SR-based Mossbauer spectroscopy enable us to observe the second-order Doppler shift, which has not been discussed, particularly for heavy Mossbauer nuclei. We have discussed the precise determination of isomer shifts and the observation of the second-order Doppler shift using 149Sm synchrotron-radiation-based Mossbauer spectroscopy.