Nuclear Resonance Absorption Of Gamma Rays In Ir-191

Mossbauer demonstrated the existence of nuclear resonance absorption of the 129-kev gamma ray of Ir/sup 191/ in metallic Ir with source and absorber at a temperature of 88 K. Mossbauer's measurements are repeated, with extension of the temperature range to 1.5 K, measurements on various foil thicknesses, and a demonstration of semiquantitative agreement of the results with theoretical calculations by Visscher based upon a theory of Lamb. (W.D.M.)