High-resolution cavity ringdown spectroscopy of the jet-cooled propyl peroxy radical C3H7O2

Abstract

We have obtained high resolution, partially rotationally resolved, jet-cooled cavity ringdown spectra of the origin band of the à ← electronic transition of two of the five conformers (G₁G₂ and G₁T₂) of the normal propyl peroxy radical, C₃H₇O₂, as well as the G conformer of the iso-propyl peroxy radical isomer. This transition, located in the near infrared, was studied using a narrow band laser source (≲250 MHz) and a supersonic slit-jet expansion coupled with an electric discharge allowing us to obtain rotational temperatures of about 15 K. All three spectra have been successfully fitted using an evolutionary algorithm approach with a Hamiltonian including rotational and spin-rotational terms. Excellent agreement with the experimental spectra was obtained by fitting seven molecular parameters in each of the ground and the first excited electronic states as well as the band origin of the electronic transition. These parameters are compared with the results from electronic structure calculations. This analysis confirms unambiguously the previous room-temperature conformer assignments that were based upon quantum chemistry calculations.