Phonons in solid argon monolayers.

Department ofPhysics and Astronomy, University ofDelaware, Newark, Delaware 19716 (Received 21 June 1989) Inelastic neutron scattering studies of excitations in ' Ar solid monolayers show a large thermal broadening of the scattered intensity between T =4 and 45 K. %'e find this thermal broadening can be readily explained in terms of anharmonic interactions between the phonons in the monolayers. The phonon energies and lifetimes, calculated using the self-consistent phonon theory, are also very 0 sensitive to the nearest-neighbor spacing aNN as well as temperature. For aNN 3.98 A, the floating monolayer is predicted to be mechanically unstable to vibration.