Laser cooling of the vibrational motion of Na_2combining the effectsof zero-width resonances and exceptional points

摘要

We propose various scenarios for molecular vibrational cooling combining the effects of two kinds of resonancestates occurring during the photodissociation of Na_2taken as an illustrative example. Such resonances result froman appropriate sampling of laser parameters (wavelength and intensity): (a) For particular choices of intensityand wavelength, two resonance energies can be brought to complete coalescence, with their positions and widthsbecoming equal and leading to a so-called exceptional point (EP) in the parameter plane. Advantage can be takenfrom such points for very selective laser-controlled vibrational transfer strategies. (b) For specific intensities, farbeyond the perturbation regime, some resonances can have a zero width (infinite lifetime). They are referred to asa zero-width resonance (ZWR) and may be used for vibrational purification purposes. We show how appropriatelyshaped, experimentally reachable laser pulses, encircling EPs or inducing ZWRs, may be used for a thoroughand comprehensive control aiming at population transfer or purification schemes, which, starting from an initialfield-free vibrational distribution, ends up in the ground vibrational level.