Nuclear resonant scattering of synchrotron radiation by Sb-121 and Sm-149

The first observation of the nuclear resonant scattering from the 37.1-keV level of Sb-121 and the 22.5-keV level of Sm-149 excited by synchrotron rad iation is reported. Delayed emission of fluorescent K or L X-rays following the internal conversion process is mainly used to observe this resonance. The evaluated energy of each excited level was 37.147 +/- 0.023 keV for Sb- 121 and 22.496 +/- 0.022 keV for Sm-149. Each half-life of the excited leve l was evaluated to be 3.37 +/- 0.39 ns for Sb-121 and 7.40 +/- 1.15 ns for Sm-149. These values agree well with the reported values for each level.