Rotational excitations in two-color photoassociation

TL;DR

This paper demonstrates a method to excite higher rotational states in ultracold molecules via two-color photoassociation, overcoming the usual suppression of such states at ultracold temperatures.

Contribution

It introduces a scheme using two lasers to induce higher rotational states in ultracold photoassociation, involving strong continuum-bound coupling and dressed states.

Findings

Higher J states can be selectively excited using the proposed two-laser scheme.

Strong laser fields modify continuum states, enabling access to higher rotational levels.

The method provides a new pathway for controlling rotational states in ultracold molecules.

Abstract

We show that it is possible to excite higher rotational states J > 2 in ultracold photoassociation by two laser fields. Usually higher J states are suppressed in photoassociation at ultracold temperatures in the regime of Wigner threshold laws. We propose a scheme in which one strong laser field drives photoassociation transition close to either J = 1 or J = 2 rotational state of a particular vibrational level of an electronically excited molecule. The other laser field is tuned near photoassociation resonance with J > 2 rotational levels of the same vibrational state. The strong laser field induces a strong continnum-bound dipole coupling. The resulting dipole force between two colliding atoms modifies the continnum states forming continnum-bound dressed states with a significant component of higher partial waves in the continnum configuration. When the second laser is scanned near the resonance of the higher J states, these states become populated due to photoassociative transitions from the modified continnum.