Anharmonic Vibrational Spectrum and Experimental Matrix Isolation Study of Thioformic Acid Conformers -- Potential Candidates for Molecular Cloud and Solar System Observations?

TL;DR

This study combines computational and experimental methods to analyze the vibrational spectra and photoisomerization of thioformic acid and its analogues, proposing TFA as a candidate for interstellar detection.

Contribution

It provides new computational vibrational spectra and experimental insights into photoisomerization of TFA and its analogues, highlighting their relevance for space chemistry.

Findings

TFA has distinct anharmonic vibrational features relevant for detection.

Photoisomerization channels of HCOSH are characterized experimentally.

TFA is proposed as a potential molecule for interstellar and planetary observations.

Abstract

Thioformic acid (TFA) is the sulfur analog of formic acid, the simplest organic acid. It has three analogues HCOSH, HCSOH, and HCSSH, each of them having two rotational isomeric (rotameric) forms: trans and cis where the trans form is energetically more stable. In this article, we study computational energetics and anharmonic vibrational spectrum of TFA including overtone and combination vibrations. We also studied experimental photoisomerization and photodecomposition channels of HCOSH molecules with different wavelengths. We suggest that TFA is a potential sulfur containing candidate molecule for interstellar and planetary observations and discuss these in a light of different radiation environments in space. More generally, we discuss that infrared radiation driven photo-isomerization reactions may be a common phenomenon in such environments and can affect the chemical reaction pathways of organic and other interstellar molecules.