First experiments on the observation of gamma resonance of a long-lived 109m Ag isomer using a gravitational gamma spectrometer

The first measurements of the resonant Mossbauer self-absorption of the long-lived 109m Ag isomer gamma rays as a function of the declination angle of the gamma beams from the horizontal direction are presented for a gamma source that represents a single-crystal silver plate doped with a parent 109Cd nuclide. The resonant absorption is manifested as a minimum of the counting rate ratio of the 109m Ag and 241Am (control gamma source) gamma-line intensities at a zero-declination angle for one of two detectors and an angle of about 1° for another detector. The magnitude of the effect is in agreement with the results of our previous experiments performed on another setup. It follows, from the data obtained, that the angular width of the gamma-resonance profile is less than two degrees, which corresponds to a broadening factor of the Mossbauer gamma line of less than five. The value of this factor calculated from the measured relative magnitude of the 109m Ag gamma-ray resonant absorption is 6.3 −1.9 +5.2 .