Vibrational dynamics in solid α-oxygen: Experimental assessment of spin-phonon couplings

The dynamics of α-oxygen is investigated by means of high-resolution inelastic neutron scattering. The generalized frequency distribution for vibrational motions is derived from the large-angle spectra. A comparison of spectra on both sides of the →α{β} magnetic ordering transition provides a clear indication of the extent of the coupling between the magnetic and lattice degrees of freedom. The specific heat and vibrational mean-square amplitudes are calculated from the spectra and compared with experimental and ab initio results. The latter also aids with the assignment of the spectral features, and to reconcile the present observations with previous measurements.