Observation of above-threshold dissociation of Na-2(+) in intense laser fields

We report the observation of above-threshold dissociation of a multielectron molecular system, Na-2(+). The process is due to continuum-continuum transitions in a field-dressed molecular continuum. Three well-resolved fragmentation channels with different kinetic energy release patterns have been detected, of which two are associated with ordinary photodissociation via "light-induced potentials" into Na(3s)+Na+ and Na(3p)+Na+, and one with continuum-continuum transitions and above-threshold dissociation into Na(3p)+Na+. We show that when we dress this molecule with a field whose intensity is similar to 3 X 10(12) W/cm(2), above-threshold dissociation prevails over other processes, such as field ionization followed by Coulomb explosion.