Controlling vibrational cooling with Zero-Width Resonances: An adiabatic Floquet approach

TL;DR

This paper introduces an adiabatic Floquet control method utilizing Zero-Width Resonances to efficiently protect and cool specific vibrational states in molecules during photodissociation, surpassing previous non-adiabatic approaches.

Contribution

It develops a quantum adiabatic control theory based on Floquet Hamiltonian to selectively protect vibrational states using ZWRs, enabling more efficient vibrational cooling.

Findings

ZWRs can be used to protect vibrational states during laser control.

Adiabatic Floquet approach improves vibrational state protection over non-adiabatic methods.

A semiclassical map of ZWRs guides optimal control strategies.

Abstract

In molecular photodissociation, some specific combinations of laser parameters (wavelength and intensity) lead to unexpected Zero-Width Resonances (ZWR), with in principle infinite lifetimes. Their interest in inducing basic quenching mechanisms have recently been devised in the laser control of vibrational cooling through filtration strategies [O. Atabek et al., Phys. Rev. A87, 031403(R) (2013)]. A full quantum adiabatic control theory based on the adiabatic Floquet Hamiltonian is developed to show how a laser pulse could be envelop-shaped and frequency-chirped so as to protect a given initial vibrational state against dissociation, taking advantage from its continuous transport on the corresponding ZWR, all along the pulse duration. As compared with previous control scenarios actually suffering from non-adiabatic contamination, drastically different and much more efficient filtration goals are achieved. A semiclassical analysis helps in finding and interpreting a complete map of ZWRs in the laser parameter plane. In addition, the choice of a given ZWR path, among the complete series identified by the semiclassical approach, amounts to be crucial for the cooling scheme, targeting a single vibrational state population left at the end of the pulse, while all others have almost completely decayed. The illustrative example, offering the potentiality to be transposed to other diatomics, is Na2 prepared by photoassociation in vibrationally hot but translationally and rotationally cold states.