The quantum mean square displacement of thermalized CO on Cu(100) in the short time approximation

Abstract

The mean square displacement 〈(x(t) − x(0))²〉 of the position x of a CO molecule adsorbed at thermal equilibrium on a Cu(100) substrate and moving along the 〈100〉 direction is evaluated quantum mechanically. The problem is treated in the independent particle formalism via the numerical solution of the time dependent Schrödinger equation with an initial thermal wave packet. The results are discussed in relation to observables from neutron scattering or helium-3 spin-echo experiments, and their interpretation in terms of classical or quantum mechanical expressions for the mean square displacement.