Application of the rotational diffusion model to the CARS spectra of high‐temperature, high‐pressure water vapour

Abstract

CARS spectra of water vapour at elevated pressures (1-16 bar) and temperatures (300-800 K) have been investigated experimentally and theoretically. A theoretical model of the CARS spectrum of water vapour based on Gordon's rotational diffusion model was tested. The model was adapted to include the effects of vibrational relaxation and dephasing processes. Good agreement was found between experiment and theory for all conditions investigated. Rotational inelastic collisions are dominant and contribute approximately 65% to the overall individual molecular linewidths. As part of the data analysis a new measurement of do/dfl (H20) = 1.10 X * 20% m2 sr-l has been made.

N2-, O2-, and air-broadened half-widths, their temperature dependence, and line shifts for the rotation band of H216O

“…Some of these catalogues contain collisionalbroadening information based on the Voigt or Van-Vleck Weisskopf profile model. Often it is necessary to account for deviations from this model, such as collisional narrowing effects [10,11], and effects from velocity changing collisions [12][13][14][15][16], line-mixing as in H 2 O Raman Q-branch spectra [17][18][19], finite duration of collision effects in the far wings of the lines [20], atmospheric continua [21][22][23] and high pressure spectra [24].…”

Pure rotational Coherent anti‐Stokes Raman spectroscopy of water vapor and its relevance for combustion diagnostics

“…Measurements in a wider range of conditions were performed by Hall et al . and Greenhalgh et al . to study the suitability of the technique for combustion applications.…”

“…[18] The first vibrational CARS spectra of the gas phase of water were recorded by Hall et al [19] already in 1979. Measurements in a wider range of conditions were performed by Hall et al [20] and Greenhalgh et al [21] to study the suitability of the technique for combustion applications. The technique has subsequently been successfully applied in different combustion situations.…”

An ultrafast algorithm for ultrafast spectroscopy

“…N2, H2, and CO-, whose rotational and vibrational motions are well described by simple quantum mechanical models 12 . Numerical CRS codes for the vibrational spectra of a handful of triatomic molecules, such as CO2, N2O and H2O 13,14 , are also available. The extension of these codes to simulate the spectra of larger polyatomic molecules is complicated by the substantial number of vibrational modes to consider, as well as by the possibility of mode coupling (e.g.…”