Molecular heat pump for rotational states

TL;DR

This paper presents a theoretical study of a molecular heat pump that uses laser-induced coupling and adiabatic passage techniques to efficiently cool molecular rotational states via sympathetic cooling with laser-cooled atoms.

Contribution

It introduces a novel cooling scheme for molecular rotational levels using adiabatic passage and sympathetic cooling, achieving over 98% efficiency with realistic parameters.

Findings

Achieved over 98% efficiency in population transfer using chirped adiabatic rapid passage.

Demonstrated robustness of adiabatic methods for molecular cooling.

Applicable to atomic systems beyond molecules.

Abstract

In this work we investigate the theory for three different uni-directional population transfer schemes in trapped multilevel systems which can be utilized to cool molecular ions. The approach we use exploits the laser-induced coupling between the internal and motional degrees of freedom so that the internal state of a molecule can be mapped onto the motion of that molecule in an external trapping potential. By sympathetically cooling the translational motion back into its ground state the mapping process can be employed as part of a cooling scheme for molecular rotational levels. This step is achieved through a common mode involving a laser-cooled atom trapped alongside the molecule. For the coherent mapping we will focus on adiabatic passage techniques which may be expected to provide robust and efficient population transfers. By applying far-detuned chirped adiabatic rapid passage pulses we are able to achieve an efficiency of better than 98% for realistic parameters and including spontaneous emission. Even though our main focus is on cooling molecular states, the analysis of the different adiabatic methods has general features which can be applied to atomic systems.