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.

Uniform Supersonic Expansion for FTIR Absorption Spectroscopy: The nu(5) Band of (NO)(2) at 26 K.

A high-resolution Fourier transform interferometer (Bruker IFS 120 HR) was combined with a uniform supersonic expansion produced by means of axisymmetric Laval nozzles. The geometry profile of the nozzle enabled us to work under precise thermodynamic and kinetic conditions. The effect of the cooling rate of different nozzles on cluster nucleation is illustrated. The experimental sensitivity was tested by recording the nu(5) band of (NO)(2) at 26 K. Copyright 2000 Academic Press.

Spectral Lineshape Parameters Revisited for HF in a Bath of Argon.

The test of an interaction potential for HF-argon recently determined from the spectroscopy of the Van der Waals complex requires accurate experimental widths and shifts cross sections. Since inconsistencies existed between previous measurements, collisional lineshapes were studied at T = 296 K by high-resolution Fourier transform spectroscopy for the 0-0, 0-1, and 0-2 bands. The accurate close-coupling molecular scattering calculations of Green and Hutson (1994. J. Chem. Phys. 100, 891) were extended to a complementary set of kinetic energies in order to check the thermal averaging procedure. Agreement between measured and computed room temperature cross sections is excellent for the three vibrational bands. This confirms the accuracy of the HF-argon surface and particularly its dependence on the HF vibrational level, which is sensitively probed both by the widths and by the shifts cross sections at high j(i) values. Copyright 1999 Academic 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.