Vibrational Spectra, DFT Calculations, and Assignments of the syn and the gauche Forms of Vinylphosphine

Infrared spectra (3500-600 cm(-1)) of vinylphosphine and its P-dideuterated derivative in the gas phase were recorded at 1 cm(-1) resolution. Both the infrared absorption bands of the syn and gauche conformers of the vinylphosphine were observed and assigned. The assignment was based on density functional theory calculations performed at the B3LYP/6-311G(d) level. The agreement between calculated and observed frequencies for both CH(2)&dbond;CHPH(2) and CH(2)&dbond;CHPD(2) was fairly good. The integrated intensities of isolated and overlapping vibrational bands were determined experimentally. Copyright 2001 Academic Press.

Line-Mixing Effects in Q Branches of CO2

A theoretical model based on the energy corrected sudden (ECS) approximation is used in order to account for line-mixing effects in Delta left and right arrow Pi infrared Q branches of 12C16O2. Its quality is demonstrated by comparisons with numerous laboratory spectra of CO2-He and CO2-N2 mixtures: three Q branches in the 4 and 17 μm regions are investigated at room temperature in a wide pressure range. The influence of mixing between Q(J) lines associated with odd and even values of the rotational quantum number J is demonstrated and analyzed in detail. It is shown that, in contrast to available fitting law approaches, the ECS model correctly predicts the influence of the parity of the rotational quantum numbers J and J' on coupling between the Q(J) and Q(J') lines. Comparisons between the effects of collisions of CO2 with N2 and He are made and analyzed. They show that these two systems involve different line couplings within the Q branch. Copyright 1997 Academic Press. Copyright 1997Academic Press

Infrared collision-induced absorption by O2 near 6.4 microm for atmospheric applications: measurements and empirical modeling

Accurate measurements of collision-induced absorption by O(2) and O(2)-N(2) mixtures in the fundamental band near 6.4 microm have been made. A Fourier-transform spectrometer was used with a resolution of 0.5 cm(-1). Absorption has been investigated in the 0-20-atm and 193-293 K pressure and temperature ranges, respectively. The current measurements confirm that the broad O(2) continuum carries small features whose attribution is not yet clear. Available experimental data in the 190-360 K temperature range have been used to build a simple, low cost computer, empirical model that is well adapted for computation of atmospheric O(2) absorption. Tests show that it is accurate, contrary to predictions of widely used atmospheric transmission codes.

Measurements and empirical modeling of pure CO(2) absorption in the 2.3-νm region at room temperature: far wings, allowed and collision-induced bands

Measurements of pure CO(2) absorption in the 2.3-μm region are presented. The 3800-4700-cm(-1) range has been investigated at room temperature for pressures in the 10-50-atm range by using long optical paths. Phenomena that contribute to absorption are listed and analyzed, including the contribution of far line wings as well as those of the central region of both allowed and collision-induced absorption bands. The presence of simultaneous transitions is also discussed. Simple and practical approaches are proposed for the modeling of absorption, which include a line-shape correction factor χ that extends to approximately 600 cm(-1) from line centers.

Collision-induced absorption in the fundamental band of N(2): temperature dependence of the absorption for N(2)-N(2) and N(2)-O(2) pairs

The collision-induced absorption fundamental band of N(2) has been investigated in the 2100-2600 cm(-1) spectral region. Laboratory measurements have been undertaken over the temperature range 193-297 K. Binary-absorption coefficients for N(2) absorption induced by collisions with N(2) and O(2) are reported and compared with N(2) temperature-dependent continua from atmospheric measurements.

Line shape in the low frequency wing of self- and N(2)-broadened v(3) CO(2) lines: temperature dependence of the asymmetry

The shape of the far wing of self- and N(2)-broadened CO(2) lines has been investigated in the 2150-2250-cm(-1) spectral region, i.e., on the low wavenumber side of the lines of the very intense v(3) band of (12)C(16)O(2) in a temperature range of atmospheric interest (200-300 K). The experimental results have been compared to calculated values based on the AFGL 1986 compilation. It appears that a symmetrical sub-Lorentzian line shape based on experiments made on the high wavenumber side cannot reproduce experiments. Comparison with experiments made at room temperature shows that the asymmetry of the correcting line shape factor chi strongly increases when decreasing the temperature.

Line shape in the low-frequency wing of N(2) and O(2) broadened CO(2) lines

The shape of the far wings of N(2) and O(2) broadened CO(2) lines have been investigated, at room temperature, in the 2140-2250-cm(-1) spectral region, i.e., on the low wavenumber side of the lines of the most intense band (nu(3) of (12)C(16)O(2)). The experimental results have been compared with calculated values based on the AFGL 1982 compilation. From this comparison it appears that the wings of the lines on the low wavenumber side of the centers decay much more rapidly than do Lorentz lines, by about the same amount as has been previously shown for the high wavenumber side. However, an asymmetrical correcting line shape factor is needed to obtain good agreement between experimental and synthetic spectra for wavenumbers sigma less, similar 2190 cm(-1).

Line shape in the low-frequency wing of self-broadened CO(2) lines

The shape of the far wings of self-broadened CO(2) lines has been investigated in the spectral region (2140-2250 cm(-1).), i.e., on the low wavenumber side of the lines of the most intense band (upsilon(3) of(12)C(16)O(2)). The experimental results have been compared to calculated values based on the AFGL 1982 compilation. From this comparison it appears that the wings of the lines on the low wavenumber side of the centers decay much more rapidly than do Lorentz lines, by about the same amount as has been previously shown for the high wavenumber side. However, an asymmetrical correcting line shape factor is needed to obtain good agreement between experimental and synthetic spectra.

Air broadened linewidths, intensities, and spectral line shapes for CO(2) at 4.3 microm in the region of the AMTS instrument

The absolute intensities and air-broadening coefficients, together with their temperature dependence have been determined for a series of very high-J R lines in the nu(3) band of CO(2) located in the spectral region of some Advanced Moisture and Temperature Sounder (AMTS) channels. These channels are located in the transmission microwindows limited by these lines. The temperature dependence of the absorption coefficient in these microwindows has been measured for N(2) and O(2) broadening. It has been clearly demonstrated that a correcting shape factor chi(sigma) independent of T cannot provide a good agreement between observed and calculated absorption in the range 193 K </= T </= 300 K for the spectral region of the AMTS channels.

Temperature dependence of the absorption in the region beyond the 4.3-microm band head of CO(2) . 2: N(2) and O(2) broadening

In this paper we present the first accurate determination, from laboratory measurements, of the temperature dependence of CO(2) continuous absorption beyond the v(3) band head, with N(2) and O(2) as perturbers. The chi form factors previously published have been tested and optimized, and new form factors are proposed. It has been clearly demonstrated for N(2), as well as for O(2) broadening, that a chi factor independent of T in the range 193 </= T </= 300 K gives calculated values of the absorption coefficient in fair agreement (+/-20% level) with observed values in the spectral region 2400 < sigma < 2500 cm(-1) .

Temperature dependence of the absorption in the region beyond the 4.3-microm band head of CO(2). 1: Pure CO(2) case

The temperature dependence of the high frequency far wings of the self-broadened CO(2) lines has been investigated in the 2400-2600-cm(-1) spectral region. The temperature dependence of the corrective shape factor X(sigma,T) is demonstrated for the first time.

Réalisation d'un spectromètre infra-rouge de résolution moyenne, corrigé de la coma

A middle resolution spectrometer according to a symmetrical Z-shaped setup in a vertical plane is described. The arrangement with the slits over and under the grating reduces coma and eliminates unwanted reflections.