The most stable isomer of H$_2$C$_4$-(OCS)$_2$ van der Waals complex: Theory and experiment agree on a structure with C2 symmetry

TL;DR

This study combines experimental infrared spectroscopy and theoretical calculations to identify and confirm the most stable C2 symmetric structure of the H$_2$C$_4$-(OCS)$_2$ van der Waals complex.

Contribution

It provides the first experimental spectrum of the complex and confirms the structure through theoretical calculations, demonstrating agreement between experiment and theory.

Findings

The complex has C$_2$ symmetry.

Experimental and theoretical results agree on the structure.

The identified structure is the most stable form.

Abstract

We report the infrared spectrum of H$_2$C$_4$-(OCS)$_2$ trimer in the region of the nu1 fundamental vibration of the OCS monomer. The van der Waals complexes are generated in a supersonic slit-jet apparatus and probed using a rapid-scan tunable diode laser. Both H$_2$C$_4$-(OCS)$_2$ and D$_2$C$_4$-(OCS)$_2$ are studied. Analysis of their spectra establishes that the trimer has C$_2$ point group symmetry. Theoretical calculations performed to find stationary points on the potential energy surface confirm that the observed structure is the most stable form. The experimental rotational parameters are in very good agreement with those computed using double hybrid functionals.