Transferring vibrational population between electronic states of diatomic molecules via light-induced-potential shaping

We investigate two-photon, selective excitation of diatomic molecules with intense, ultrafast laser pulses. The method involves transfer of a vibratio nal population between two electronic states by shaping of light-induced po tentials (LIPs). Creation and control of the LIPs is accomplished by choosi ng pairs of transform-limited pulses with proper frequency detunings and ti me delays. Depending on the sequence of pulses (intuitive or counter-intuit ive) and on the sign of the detuning (below or above the first transition) four schemes are possible for population transfer by LIP shaping. We develo p a simple analytic model to predict the optimal laser pulses, and to model the adiabatic dynamics in the different schemes. Based on a harmonic, thre e-state model of the sodium dimer we demonstrate numerically that all four schemes can lead to efficient, selective population transfer. A careful ana lysis of the underlying physical mechanisms reveals the varying roles playe d by the adiabatic and diabatic crossings of the LIPs. The detailed mechani sms influence the robustness and experimental applicability of the schemes. (C) 2001 American Institute of Physics.