We report the observation of above-threshold dissociation of a multielectron molecular system, $\mathrm{Na}_2{}^{+}$. 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 $\mathrm{Na}\left(3s\right)+{\mathrm{Na}}^{+}$ and $\mathrm{Na}\left(3p\right)+{\mathrm{Na}}^{+}$, and one with continuum-continuum transitions and above-threshold dissociation into $\mathrm{Na}\left(3p\right)+{\mathrm{Na}}^{+}$. We show that when we dress this molecule with a field whose intensity is $\sim 3\times {10}^{12}\mathrm{W}∕{\mathrm{cm}}^2$, above-threshold dissociation prevails over other processes, such as field ionization followed by Coulomb explosion.

• Received 25 February 2008

DOI:https://doi.org/10.1103/PhysRevA.78.021403