SELECTIVE EXCITATION OF NUCLEAR SUBLEVELS

A method is described for selectively populating any one of the sublevels of a nuclear excited state by means of the Mössbauer effect. Specifically, a single hyperfine level of the 14.4-keV state of Fe57 was populated using a constant-velocity drive system, a single-line Co57 source, and a metallic Fe57 scatterer arranged in 90°scattering geometry. Polarization was detected by analyzing the scattered radiation with a second Mössbauer drive and a single-line absorber. Two applications of the selective excitation process are also reported. In the first, the energy distribution of the scattered radiation was studied as a function of the Doppler shift of the incident radiation. In the second, NMR transitions between the hyperfine sublevels of the 100-nsec state of Fe57 were directly observed. © 1969 The American Physical Society.