Resonance-enhanced two-photon dissociation ofH2through nonadiabatically coupled intermediate and final states

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Abstract
Nonperturbative time-dependent calculations of the resonance-enhanced two-photon dissociation probability of H2 in two frequency laser fields from the ground X1Σg+(v=0,j=0) level to the final continua of GK1Σg+ and I1Πg states have been made as functions of the laser frequencies. The two fields are taken to have linear parallel polarizations with identical sine-squared time dependences of the amplitudes. The first field of frequency ω1 is near resonant with the two closely spaced excited intermediate levels B1Σu+(v=14,j=1) and C1Πu+(v=3,j=1), which are strongly coupled to each other through nonadiabatic interaction as well as by radiative Raman coupling. Thus two intermediate levels with mixed Σ+−Π+ character are created. The molecule finally dissociates through coherent excitation to a number of near-resonant discrete rovibrational bound levels of HH¯1Σg+ and J1Δg+ embedded into the continua of GK and I states as well as by direct transition to these continua, by absorption of a second photon of frequency ω2. The nonadiabatic interactions of the bound levels of HH¯ and J states, with the respective continuum of GK and I states, give these levels a predissociating character. The interference of the direct transition amplitudes to the continua, and those through the various overlapping predissociating resonances, gives rise to a resultant structure in the dissociation probability with the variation of ω2. The bound levels used are either (a) a group of three closely spaced vibrational-rotational levels, HH¯1Σg+ (v=4, j=0 and 2), J1Δg(v=4,j=2); and (b) the next group of three closely spaced levels,