Anharmonic resonances in the CH chromophore overtone spectra of CHBrF2

Andrea Pietropolli Charmet (1) , Nicola Tasinato (1) , Paolo Stoppa (1) , Santi Giorgianni (1) , Alberto Gambi (2)

1 Dipartimento di Scienze Molecolari e Nanosistemi
2 Dipartimento di Chimica, Fisica e Ambiente

The gas phase Fourier transform infrared spectra of bromodifluoromethane, CHBrF2, have been recorded up to 10100 cm-1 with a resolution of 0.5 cm-1. All the most relevant absorptions in the overtone region have been ascribed to the CH chromophore. 26 bands involving either the CH-stretching (ν1) and bending (ν2, ν7) modes have been assigned and their relative band strengths have been determined. The vibrational analysis of the corresponding polyads (up to N = 7/2) has been performed by means of an effective Hamiltonian which takes into account anharmonic resonances, thus leading to the determination of Fermi and Darling-Dennison coupling terms. The obtained effective spectroscopic parameters have been able to quantitatively describe both the position and intensity of all the absorption bands, and also to rationalize the effects and the magnitudes of the various resonances in each polyad. The results obtained by this approach have been compared with those computed by using high quality ab initio electronic structure calculations employing the second order vibrational perturbation theory (VPT2). An overall satisfactory agreement between the observed and the ab initio computed values has been obtained by properly taking into account in the final calculations the relative magnitude of Fermi and Darling-Dennison resonance effects into each polyad.

Mots clés: Physical Sciences

Domaines: Matière Condensée [cond-mat]

Andrea Pietropolli Charmet, Nicola Tasinato, Paolo Stoppa, Santi Giorgianni, Alberto Gambi. Anharmonic resonances in the CH chromophore overtone spectra of CHBrF2. Molecular Physics, 2011, pp.1. ⟨10.1080/00268976.2011.609138⟩. ⟨hal-00723869⟩