Manipulation of Bond Hardening in H 2 + by Chirping of Intense Femtosecond Laser Pulses

Bond hardening of ${\mathrm{H}}_{2}^{+}$ has been observed in the intensity range of $100--200\mathrm{TW}/{\mathrm{cm}}^{2}$ using 792 nm laser pulses. This effect can be understood in terms of a light-induced potential well created at twice the normal (free) equilibrium internuclear distance by an adiabatic mixing of 1- and 3-photon resonances. The trapped population dissociates into ${\mathrm{H}}^{+}$ and H when the potential well becomes convex on the trailing edge of the pulse. The dynamics of the nuclear wave packet was manipulated by chirping the pulse duration from 45 to 500 fs and observing a reduction of the kinetic energy release from 0.3 to 0.0 eV. This energy shift is interpreted as a dynamic Raman effect within the laser bandwidth.