Coherent transient effects in Mössbauer spectroscopy due to phase modulation of recoilless $\gamma$ radiation are considered both theoretically and experimentally. Absolute calibration of the source motion in the angstrom range and separation of the source and absorber contributions to the experimental linewidth were obtained from a single transient Mössbauer spectrum. A new phase-modulation method for generating short enhanced recoilless $\gamma$ pulses is introduced.

• Received 8 July 1982

DOI:https://doi.org/10.1103/PhysRevLett.49.1209