Chirp effect on the kinetic energy release upon dissociation of H$_{2}^{+}$ in intense ultrashort laser pulses

The effect of chirp on the kinetic energy release (KER) of the vibrational states of H$_{2}^{+}$ was measured using a coincidence 3D momentum imaging technique. The data shows significant shifts of the KER peaks associated with the dissociating vibrational levels in intense 70 and 120 fs pulses chirped positively/negatively from the 30 fs transform limited pulses. Our calculations show that this energy shift is due to the dissociation of the H$_{2}^{+}$ early in the pulse -- when the photon energy is shifted to either higher or lower energy depending on the chirp. This effect is reduced by intensity averaging, but it is still a measurable effect.