Testing the phonon spectrum of metallic chromium with the nuclear-resonance photon scattering technique

The nuclear-resonance photon-scattering cross section σs from Cr50 in a metallic form was studied as a function of temperature in the range 15-300 K. The value of σs was used for deducing the effective temperature Te which is related to a weighted average of the phonon spectrum of metallic Cr. This Te is also a measure of the total zero-point kinetic energy of the lattice and was used to define another Debye temperature FTHETA0; its value for metallic Cr was measured and found to be FTHETA0=510±20 K. This value is higher by about 10% than that obtained from the known phonon spectrum deduced by inelastic neutron scattering. A similar deviation occurs in other elements. The reason for this deviation of the values of Te and hence of FTHETA0 obtained by the nuclear-resonance photon-scattering technique and by inelastic neutron scattering is discussed.