Photolysis of HCOOH monomer and dimer in solid argon: Raman characterization of in situ formed molecular complexes

Abstract

Raman spectroscopy combined with the matrix isolation technique was employed to study the 193-nm photodecomposition products of formic acid in an argon matrix. The Raman-active fundamentals belonging to the CO₂ + H₂ and CO + H₂O photoproducts were assigned. Also, bands due to Fermi resonance between the stretching vibration (ν₁) and the overtone of the bending mode (2ν₂) of CO₂ were identified. Both ortho- and para-H₂ molecules were identified from their rotational lines S₀(1) and S₀(0), respectively. These bands appeared upon matrix annealing as well as after prolonged photolysis. Additionally, photolysis of FA dimers produces oxalic acid and its secondary photoproducts, CO₂ + CO + H₂O. All experimental studies were supported by ab initio calculations.