# Directional Quantum-Controlled Chemistry: Generating Aligned Ultracold Molecules via Photoassociation

## TL;DR

This paper demonstrates that pulsed photoassociation of ultracold rubidium atoms can produce aligned molecules, with enhanced formation rates and alignment achieved through frequency-chirped and synchronized multiple pulses.

## Contribution

It introduces a theoretical approach to control molecular alignment and formation rates in ultracold molecules using tailored laser pulses.

## Key findings

- Transform-limited pulses produce significant alignment.
- Frequency-chirped pulses increase formation rate but slightly reduce alignment.
- Multiple synchronized pulses coherently enhance population and alignment.

## Abstract

Photoassociation of ultracold atoms is shown to lead to alignment of the product molecules along the excitation laser polarization axis. We theoretically investigate pulsed photoassociation of $^{87}Rb$ atoms into a specific weakly-bound level of the a $^3\Sigma_u^+$ metastable electronic state and find both stationary and time-dependent field-free alignment. Although a transform-limited pulse yields significant alignment, a frequency-chirped pulse dramatically enhances the molecular formation rate at the cost of a slight decrease in the alignment. Employing multiple pulses synchronized with the vibrational and rotational periods leads to coherent enhancement of both population and alignment of the target state.