Precise determination of hyperfine interactions and second-order doppler shift in 149Sm Mössbauer transition
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We have succeeded in precisely determining the hyperfine interactions, particularly the isomer shifts, in the 149Sm Mössbauer 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 Mössbauer spectroscopy is difficult. The recent development of synchrotron-radiation-based Mössbauer 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 Mössbauer 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 Mössbauer spectroscopy enable us to observe the second-order Doppler shift, which has not been discussed, particularly for heavy Mössbauer nuclei. We have discussed the precise determination of isomer shifts and the observation of the second-order Doppler shift using 149Sm synchrotron-radiation-based Mössbauer spectroscopy.
KeywordsSynchrotron-radiation-based Mössbauer spectroscopy Isomer shift Second-order Doppler shift 149Sm Mössbauer effect Time-window effect
The authors appreciate Yoshio Kobayashi, Jin Nakamura, Shota Amagasa, Yasuhiro Yamada, Michael K. Kubo, Wataru Sato, Yasuhiro Kobayashi, and Hisao Kobayashi for their experimental assistance of 149Sm SR Mössbauer spectroscopy. The authors also appreciate Akira Yamada, Ryuji Higashinaka, Tatsuma D. Matsuda, Yuji Aoki, Yusei Shimizu, Hiroyuki Hidaka, Tatsuya Yanagisawa, Hiroshi Amitsuka, and Fumitoshi Iga for the preparation of high quality samples. The present work was carried out under the approval of JASRI (2015A2036, 2015B1947, 2016A1281, 2016B1057, 2016B1967, 2017A1060, 2017B1275). This work was partially supported by Grants-in-Aid for Scientific Research B (15H03697) and Challenging Exploratory Research (15K14170).
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