A New Laser Cooling Concept for Molecular Translational Motion

Abstract

We propose a laser cooling concept for the translational motion of molecules which does not require repeated spontaneous emission by each molecule. The cooling works by repetition of three main steps: velocity selection of a narrow momentum width, deceleration of velocity selected molecules and accumulation of the decelerated molecules by an irreversible process, namely by single spontaneous emission. We develop a cooling model which enables analytical description of the transient populations and entropies for the total molecular system, the center of mass degree of freedom and the internal degrees of freedom. Simulation shows that the cooling process can reduce a large momentum width to a final width which in principle can be arbitrarily small. Center of mass entropy is reduced while the internal entropy is increased after cooling. We show that translational cooling can occur during coherent laser interactions. The entropies change in consistency with the Araki-Lieb inequality.