Dynamic Raman processes on the rising and falling edges of intense laser pulses

In recent experiments using intense femtosecond lasers, we have observed dissociation channels of H + 2 that we ascribe to below-threshold dissociation (BTD) and zero-photon dissociation (ZPD). These dynamic Raman processes can be understood by considering the time-evolution of the adiabatic, photon-dressed curves during the passage of the laser pulse. Both processes involve vibrational trapping. Going beyond the one-dimensional model, one notes that the trapping well is in fact saddle-shaped, leading to perpendicular dissociation of the trapped wavepacket (i.e., dissociation orthogonal to the laser E-field). This phenomenon is reflected in the broad angular distribution of the high energy component of the one-photon dissociation channel.