Line Mixing Parameters Research Articles

Line Mixing Parameters in the ν 4 Rovibrational Band of NH 3 Perturbed by N 2

Pressure broadening (PB) linewidths and cross-relaxation parameters have been measured in the ν 4 rovibrational band of NH 3 (window region 1450-1600 cm −1) using diode laser and Fourier transform (FT) spectrometers. The measurements were performed using N 2 foreign gas (pressure range 0-1600 Torr) at room temperature (294 K). PB coefficients have been obtained for 40 rovibrational transitions. The overlapping lines have been analysed using our model [M. Broquier and A. Picard, Chem. Phys. Lett. 111, 602-606 (1984)] and cross-relaxation cross sections have been obtained for six rovibrational inversion doublets. Our experimental results are compared with other previous measurements obtained in the ν 2, ν 3, and ν 4 rovibrational bands of NH 3 and for several foreign gases.

A compilation of first-order line-mixing coefficients for CO 2Q-branches

A parametrization of first-order line-mixing in CO 2 Q-branches for use in atmospheric radiative transfer codes. Regression coefficients for the temperature dependence of the first-order line-mixing parameters for each J in 11 of the strongest Q-branches between 600 and 3000 cm -1 are given. These coefficients may only be used with the line strengths and widths reported in the HITRAN92 line compilation; otherwise large errors will be introduced into the calculated line shape. Other potential problems in the implementation of first-order line-mixing in radiative transfer codes are also discussed.

Discrete frequency synthesizer

In this study, we report the first experimental measurements of spectral line shape parameters (self- and air-broadened Lorentz half-widths, pressure-shifts, and line mixing (via off-diagonal relaxation matrix elements) coefficients and their temperature dependences, where appropriate) for transitions in the 2ν3 Q branch manifolds, Q(11)–Q(1) of methane (12CH4), in the 5996.5–6007-cm−1 region. The analysis included 23 high-resolution, high signal-to-noise laboratory absorption spectra recorded with the Bruker IFS-125HR Fourier transform spectrometer (FTS) at JPL. The experimental data were obtained using 12C-enriched 12CH4 and dilute mixtures of 12CH4 in dry air in the 130–296 K range using a room-temperature long path absorption cell and, two custom-built coolable cells. In the analysis, an interactive multispectrum fitting software was employed where all the 23 spectra (11 self-broadened and 12 air-broadened) were fit simultaneously. By carefully applying reasonable constraints to the parameters for severely blended lines, we were able to determine a self-consistent set of broadening, shift and line mixing (relaxation matrix coefficients) parameters for CH4–CH4 and CH4–air collisions. In the majority of cases, a quadratic speed dependence parameter common for all transitions in each Q(J) manifold was determined. However, temperature dependences of the Q branch line mixing parameter could not be determined from the present data. Since no other experimental line shape measurements have been reported for this Q-branch, the present results are compared to available values in the HITRAN2012 database.