NONTHERMAL KINETIC-ENERGY DISTRIBUTIONS OF DESORBED NA DIMERS

Experiments are reported which demonstrate that Na dimers can be desor bed in a non-thermal reaction if rough Na surfaces are irradiated with pulsed laser light of lambda=355 nm at low laser fluences. This follo ws from the kinetic-energy distributions of the dimers, which were det ermined by time-of-flight measurements using a second laser at lambda= 248 nm for photoionization. The rate of desorbed dimers can even surmo unt the rate of detached atoms. Obviously, the dimers constitute highl y stable sub-units of the surface which can be released without breaki ng into individual atoms.