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Discusses the use of an autoscan laser spectroscopy to perform a detailed study of vibrational overtones in polyatomic molecules, with applications to intramolecular dynamics and bond-selected chemistry. Experimental setup; Pressure self-broadening coefficients; Absolute line intensities.

Part II. Discusses the use of laser spectroscopy for the self-collisional lineshift measurements of the absorption band. Determining pressure-dependent line positions from an absorption spectrum recorded using a White-type multiple-pass cell; Measurement of line wavenumbers for stronger lines; Different intermolecular behavior of a molecule.

Abstract: High resolution measurements of room temperature absorption with a controlled tunable diode laser (TDL) spectrometer have been made for R(2) and P(14) lines in the HCl fundamental band perturbed by N2, Xe, Ar and He at pressures lower than one atmosphere. Pressure broadening, shift and collisional narrowing parameters have been extracted by least-squares fitting of several collisional profiles to the spectra. Asymmetries are observed for P(14) broadened by Xe at the lowest pressures and attributed to correlations between velocity- and phase-changing collisions. [Copyright &y& Elsevier]

The design of a new apparatus, named FANTASIO, for studying jet-cooled molecules is described. It includes, around the same supersonic expansion cell, a high resolution Fourier transform spectrometer with single or multipass optics, a tunable diode laser spectrometer with optional cavity ring-down facilities, and a quadrupole mass spectrometer. Performance and operational procedures are illustrated. [ABSTRACT FROM AUTHOR]

We present a line profile study at 150, 110 and 80 K for the R(7) line in the fundamental band of 13 CO perturbed by Ar in a new stabilized low-temperature cell cooled by liquid nitrogen. The broadening, shifting and narrowing parameters are determined taking into account the absorber speed dependence by simultaneous least-squares fitting of spectra over a 4-300 Torr pressure range recorded using a frequency-stabilized diode laser spectrometer. When the cell is cooled by liquid helium the (1-0) R(2) line of 13 CO in collision with helium is observed at a temperature of 6.9 K. [ABSTRACT FROM AUTHOR]

Abstract: We present a complete study on four methane lines for two atmospheric micro-windows (in the ν 2 + ν 4 absorption band) used for the determination of atmospheric methane concentrations with ground-based Fourier transform spectrometers. Thanks to our tunable diode laser (TDL) spectrometer with active wavenumber control and step-by-step recording mode we have improved the accuracy on intensity, broadening, narrowing, and pressure shift parameters. To make our results directly useable in atmospheric models which usually assume a Voigt line shape, we have parameterised an effective-broadening parameter γ Voigt (P) for each line and each gas mixture (CH4–N2 and CH4–O2). When this parameterisation is used to fit a “true” line profile, the same concentration as with more sophisticated models is retrieved using a consistent set of spectroscopic parameters in both approaches. [Copyright &y& Elsevier]

We have constructed a stabilized low temperature infrared absorption cell cooled by an open cycle refrigerator, which can run with liquid nitrogen from 250 to 80 K or with liquid helium from 80 K to a few kelvin. Several CO infrared spectra were recorded at low temperature using a tunable diode laser spectrometer. These spectra were analyzed taking into account the detailed effects of collisions on the line profile when the pressure increases. We also recorded spectra at very low pressure to accurately model the diode laser emission. Spectra of the R(2) line in the fundamental band of 13CO cooled by collisions with helium buffer gas at 10.5 K and at pressures near 1 Torr have been recorded. The He-pressure broadening parameter (γ0=0.3 cm-1 atm-1) has been derived from the simultaneous analysis of four spectra at different pressures. [Copyright &y& Elsevier]

We present measurements of Ar-broadening parameters for the R(0) and R(7) lines in the fundamental band of 13CO at eight temperatures from 80 to 297 K. The broadening parameters are determined by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The comparison of the broadening parameter values for R(7) derived at room temperature and different pressures from different line profiles shows that an empirical line profile, which takes into account narrowing effects (Dicke narrowing and absorber speed dependence) but neglects any correlation between collisions, is able to describe the observed lines with constant values of the narrowing and broadening parameters over a 10–500 Torr pressure range. Starting from a recent ab initio potential energy surface, theoretical thermally averaged close coupling values of the Ar broadening parameter are calculated for the same temperatures. The comparison between experimental and calculated values shows an overall agreement of 1.5%. [Copyright &y& Elsevier]

Collision effects on water vapor line profiles perturbed by nitrogen at room temperature have been studied by Fourier transform and tunable diode laser spectroscopy. Narrowing effect due to molecular confinement (Dicke effect) has been observed for P and Q branch lines of the ν2 band of H2O with Fourier transform spectrometer. Narrowing and broadening parameters have been determined using the soft and hard collision models. A more precise study on three R-branch lines with a frequency stabilized diode laser spectrometer allows to perform the comparison between the two collision models at low pressure and to analyze the different narrowing effects when the pressure increases taking into account the molecular confinement and the absorber speed dependent effects. [Copyright &y& Elsevier]