Control of non-Franck–Condon transitions: lighting a dark state Original Research Article

We show that pairs of intense laser pulses can be used to selectively invert vibronic population from an initial vibrational level to a chosen final vibration level. We demonstrate that robust, efficient transfer can be achieved for a case in which the overlap between the initial state and the final state is vanishingly small. Results are presented for a three-state model of the sodium dimer, Na2, in which the objective is to populate the outer well of the 1Σu(4s) double-well potential. To understand the detailed mechanism of population transfer, we analyze the structure of the adiabatic, light-induced potentials (LIPs) on which the vibrational wave packets evolve. Due to the topology of the system, non-adiabatic transitions among the potentials must also be considered. The results suggest that careful shaping of LIPs offers a general method for selective population transfer, even when the desired final state is a dark state.