Femtosecond Laser Induced Coulomb Explosion Imaging of Aligned OCS Oligmers inside Helium Nanodroplets

TL;DR

This study uses femtosecond laser pulses to align and Coulomb explode OCS dimers and trimers inside helium nanodroplets, revealing their structures through ion imaging and covariance analysis.

Contribution

It introduces a method combining laser alignment and Coulomb explosion imaging to determine the structures of OCS oligomers inside helium nanodroplets, including new structural insights.

Findings

OCS dimer has a slipped-parallel structure similar to gas phase.

OCS trimer exhibits barrel-shaped and linear chain structures.

New structural configurations are observed in helium nanodroplets.

Abstract

Dimers and trimers of carbonyl sulfide (OCS) molecules embedded in helium nanodroplets are aligned by a linearly polarized 160 ps long moderately intense laser pulse and Coulomb exploded with an intense 40 fs long probe pulse in order to determine their structures. For the dimer, recording of 2D images of OCS$^+$ and S$^+$ ions and covariance analysis of the emission directions of the ions allow us to conclude that the structure is a slipped-parallel shape similar to the structure found for gas phase dimers. For the trimer, the OCS$^+$ ion images and corresponding covariance maps reveal the presence of a barrel-shaped structure (as in gas phase) but also other structures not present in the gas phase, most notably a linear chain structure.