Showing papers by "Nicola Tasinato published in 2011"

Microwave, high-resolution infrared, and quantum chemical investigations of CHBrF2: ground and v4 = 1 states.

Abstract: A combined microwave, infrared, and computational investigation of CHBrF2 is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH79BrF2 and CH81BrF2 provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the importance of relativistic effects, which are of the order of 6.5% and included in the present work using second-order direct perturbation theory, needs to be emphasized for accurate predictions of the bromine quadrupole-coupling constants. The infrared measurements focused on the ν4 fundamental band of CH79BrF2. Fourier transfo...

Toward a Complete Understanding of the Vinyl Fluoride Spectrum in the Atmospheric Region

Abstract: A deep and comprehensive investigation of the vinyl fluoride (CH 2 CHF) spectrum in the atmospheric window around 8.7 μm is presented. At first, the ro-vibrational patterns are modelled to an effective Hamiltonian, which also takes into account the coupling of the C―F stretching vibration, ν 7 , with the neighbouring vibrational combination ν 9 + ν 12 . The obtained Hamiltonian gives very accurate simulations and predictions of the ro-vibrational quantum energies. Then, in the main part of the work, an experimental and theoretical study of vinyl fluoride self-broadening collisions is carried out for the first time. The broadening coefficients obtained experimentally are compared with those calculated by a semiclassical theory, demonstrating a significant contribution of collisional coupling effects between lines connecting pairs of degenerate (or nearly degenerate) rotational levels. Finally, the experimentally retrieved integrated absorption coefficients are used to calculate the absorption cross-section of the ν 7 normal mode, from which dipole transition moments are derived. The obtained results provide a deep insight into the spectral behaviour of vinyl fluoride, in a spectral region of primary relevance for atmospheric and environmental determinations. Indeed, the data presented constitute an accurate model for the remote sensing of vinyl fluoride—a molecule of proved industrial importance which can lead to hazardous effects in the atmosphere and affects human's health.

Anharmonic resonances in the CH chromophore overtone spectra of CHBrF2

Abstract: The gas-phase Fourier transform infrared spectra of bromodifluoromethane, CHBrF2, have been recorded up to 10,100 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. Twenty-six bands involving either the CH-stretching (ν 1) and bending (ν 2, ν 7) modes have been assigned and their relative band strengths have been determined. Vibrational analysis of the corresponding polyads (up to N = 7/2) has been performed by means of an effective Hamiltonian that takes into account anharmonic resonances, thus leading to the determination of Fermi and Darling–Dennison coupling terms. The obtained effective spectroscopic parameters were 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 using this approach have been compared with those computed using high-quality ab initio electron...