Quantum diffusion of H/Ni(111) through a Monte Carlo wave function formalism

We consider a quantum system coupled to a dissipative background with many degrees of freedom using the Monte Carlo wave function method. Instead of d ealing with a density matrix which can be very highly dimensional, the meth od consists of integrating a stochastic Schrodinger equation with a non-Her mitian damping term in the evolution operator, and with random quantum jump s. The method is applied to the diffusion of hydrogen on the Ni(111) surfac e below 100 K. We show that the recent experimental diffusion data for this system can be understood through an interband activation process, followed by quantum tunneling.