The kinetic energy release (KER) and angular distribution for dissociation and ionization of $\mathrm{N}_2{}^{+}$ in an intense short pulse $\left(7\mathrm{fs}\right)$ laser at $790\mathrm{nm}$ was measured by employing a coincidence three-dimensional momentum imaging method that provides kinematically complete information on the dissociation. At an intensity of $6.0\times {10}^{15}\mathrm{W}∕{\mathrm{cm}}^2$ a high-KER peak $(\sim 6.1\mathrm{eV})$ unexpectedly appears in the dissociation spectrum in addition to the usual low-KER peak $(\sim 0.6\mathrm{eV})$. Additionally, the KER distribution in ionization, which peaks around $7\mathrm{eV}$, has a tail that surprisingly extends well beyond the Coulomb explosion energy. Both these high-KER contributions result from dissociation pathways involving highly excited states of $\mathrm{N}_2{}^{+}$ with steep potential curves as indicated by the dressed state potential energy curves picture.

• Received 7 May 2008

DOI:https://doi.org/10.1103/PhysRevA.78.033430