# Alignment of the CS$_2$ Dimer Embedded in Helium Droplets Induced by a Circularly Polarized Laser Pulse

## TL;DR

This study demonstrates the alignment of CS$_2$ dimers embedded in helium droplets using a circularly polarized laser, revealing the orientation of the intermolecular axis through ion emission analysis.

## Contribution

It shows that helium droplets enable effective alignment of molecular dimers with circularly polarized lasers, with results matching gas-phase behavior at very low temperatures.

## Key findings

- Intermolecular C-C axis aligns perpendicular to laser polarization plane.
- Alignment degree depends on laser intensity and matches gas-phase calculations.
- Helium droplets facilitate controlled molecular alignment at cryogenic temperatures.

## Abstract

Dimers of carbon disulfide (CS$_2$) molecules embedded in helium nanodroplets are aligned using a moderately intense, 160ps, non-resonant, circularly polarized laser pulse. It is shown that the intermolecular carbon-carbon (C-C) axis aligns along the axis perpendicular to the polarization plane of the alignment laser pulse. The degree of alignment, quantified by $\langle \cos^2(\theta_\text{2D}) \rangle$, is determined from the emission directions of recoiling CS$_2$$^+$ fragment ions, created when an intense 40fs probe laser pulse doubly ionizes the dimers. Here, $\theta_\text{2D}$ is the projection of the angle between the C-C axis on the 2D ion detector and the normal to the polarization plane. $\langle \cos^2(\theta_\text{2D}) \rangle$ is measured as a function of the alignment laser intensity and the results agree well with $\langle \cos^2(\theta_\text{2D}) \rangle$ calculated for gas-phase CS$_2$ dimers with a rotational temperature of 0.4K.