Above Threshold Coulomb Explosion of Molecules in Intense Laser Pulses

We have measured and explained a new mechanism of molecular ionization near the appearance intensity that produces a sequence of peaks in the nuclear kinetic energy spectrum separated by the photon energy. Our interpretation is based on an internally consistent model for the nuclear motion during an intense laser pulse. Within this model, the same concepts and language can be used for both dissociation and ionization, leading to a more unified understanding of the dynamics.

Figure 1

(a) The diabatic Floquet potentials for $\mathrm{H}_2{}^{+}$. Besides the molecular quantum numbers, each curve carries a photon number label. (b) The same as (a), but including the ionization threshold potentials.

Figure 2

(a)–(c) Experimental ionization KER spectra. The vertical bars indicate the predicted KER peak locations, grouped by initiating mechanism. (d) Experimental log-log angular distributions corresponding to the spectra (a)–(c).