NON-EQUILIBRIUM PHONONS IN OPTICALLY PUMPED YAG-Cr3+ R.J.G. Goossens, E.E. Koldenhof, J.I. Dijkhuis and H.W. de Wijn J. Phys. Colloques, 46 C7 (1985) C7-259-C7-262 DOI: 10.1051/jphyscol:1985747