Characterization of OCS-HCCCCH and N2O-HCCCCH dimers: Theory and experiment

TL;DR

This study combines experimental infrared spectroscopy and high-level ab initio calculations to characterize the structure and energetics of OCS-HCCCCH and N2O-HCCCCH dimers, revealing their planar configurations and stable geometries.

Contribution

It provides the first detailed spectroscopic and theoretical characterization of these weakly-bound dimers, identifying their stable structures and interaction energies.

Findings

Both dimers are planar with nearly parallel monomer axes.

Experimental spectra match the lowest energy theoretical isomers.

Multiple stable geometries were identified through calculations.

Abstract

The infrared spectra of the weakly-bound dimers OCS-HCCCCH, in the region of the nu1 fundamental band of OCS (2050 cm-1), and N2O-HCCCCH, in the region of the nu1 fundamental band of N2O (2200 cm-1), were observed in a pulsed supersonic slit jet expansion probed with tunable diode/QCL lasers. Both OCS-HCCCCH and N2O-HCCCCH were found to have planar structure with side-by-side monomer units having nearly parallel axes. These bands have hybrid rotational structure which allows for estimates of the orientation of OCS and N2O in the plane of their respective dimers. Analogous bands for OCS-DCCCCD and N2O-DCCCCD were also observed and found to be consistent with the normal isotopologues. Various levels of ab initio calculations were performed to find stationary points on the potential energy surface, optimized structures and interaction energies. Four stable geometries were found for OCS-HCCCCH and three for N2O-HCCCCH. The rotational parameters at CCSD(T*)-F12c level of theory give results in very good agreement with those obtained from the observed spectra. In both dimers, the experimental structure corresponds to the lowest energy isomer.