Formation of deeply bound polar molecules combining pump-dump pulses with infrared radiation

TL;DR

This paper proposes a laser-based method to efficiently form cold, ground-state polar molecules from atomic pairs using a sequence of pump, dump, and infrared chirped pulses, optimized via control techniques.

Contribution

It introduces a novel three-step laser pulse scheme with optimized control for creating ground-state polar molecules from cold atoms.

Findings

Effective formation of ground-state molecules demonstrated

Optimized chirped pulses improve transition efficiency

Alternative to traditional photoassociation methods

Abstract

We consider the formation of cold ground-state polar molecules in a low vibrational level by laser fields. Starting from a pair of cold colliding atoms of dissimilar species, we propose a strategy consisting of three steps. In the first step, a pump pulse induces the molecule formation by photoassociating the atomic pair in a high or intermediate vibrational level of an excited electronic molecular state. This step is followed by a dump pulse in an intermediate vibrational level of the ground state. In the last step, an infrared chirped pulse induces downward transitions among the vibrational levels of the ground electronic state, reaching the ground vibrational level. Initially, the strategy is constructed with fixed-shaped pulses. Subsequently, we perform the calculations with optimized chirped pulses introducing an optimal control technique in which the optimization of the time-dependent frequency is carried out in the time domain. The proposed scheme is an alternative to the use of two pairs of pump-dump pulses or to the direct photoassociation and vibrational stabilization in the ground state.