Experimental and theoretical CO2–He pressure broadening cross sections

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Line mixing effects in the

Line mixing effects have been studied in the $\nu_3$ band of $\rm CH_3F$ perturbed by helium. Theoretical absorption coefficients are compared to FTIR measurements, which were made at room temperature for helium pressure from 1 atm up to 90 atm. The observed strong modifications with respect to additive Lorentzian contributions are explained by line coupling effects. The Infinite Order Sudden Approximation and the Energy Corrected Sudden Approximation are used in order to account for these effects. The latter gives better agreement: it rather successfully predicts the band shape and the linewidths

Infrared spectroscopy of (CO2)N nanoparticles (30<N<14500) flowing in a uniform supersonic expansion

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Uniform Supersonic Expansion for FTIR Absorption Spectroscopy: The ν5 Band of (NO)2 at 26 K

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Energy corrected sudden calculations of linewidths and line shapes based on coupled states cross sections: The test case of CO2–argon

The accuracy of the energy-corrected sudden (ECS) formalism for line shape calculations is investigated, using coupled states calculation for CO2–Ar collisions on the recently developed “single repulsion” potential of Hutson et al. [J. Chem. Phys. 107, 1824 (1997); 105, 9130 (1996)]. Inelastic cross sections σ0(L→0,E)≡Q′L(E) are calculated using the MOLSCAT program, and then averaged over Maxwell–Boltzmann kinetic energy distributions to give the thermally averaged “basic rates” Q′L(T) needed in the ECS formalism. The ECS linewidths for low initial J, Ji⩽16, are sensitive only to the low-L basic rates, for which the CS calculations are converged; comparing them with directly calculated CS linewidths thus gives a stringent test of the ECS model, and it works well (within 10%). However, for higher Ji lines and for band shape calculations, basic rates for higher L are needed for convergence. These are obtained by an extrapolation procedure based on experimental data, using an exponential power law and the adiabaticity factor recently suggested by Bonamy et al. [J. Chem. Phys. 95, 3361 (1991)] ECS calculations using the resulting basic rates are designated “extrapolated CS-ECS calculations,” and are found to give accurate results for high-Jlinewidths, for near-wing absorption and for band profiles over a very wide range of perturber pressures (up to 1000 atm)

Shifting and broadening in the fundamental band of CO highly diluted in He and Ar: A comparison with theory

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