On the role of molecular clustering on infrared absorption line shapes of acetylene in a supersonic expansion

A supersonic expansion containing acetylene seeded into Ar and produced from a circular nozzle is investigated using CW/cavity ring down spectroscopy, in the 1.5 μm range. The results, also involving experiments with pure acetylene and acetylene-He expansions, as well as slit nozzles, demonstrate that the denser central section in the expansion is slightly heated by the formation of acetylene aggregates, resulting into a dip in the monomer absorption line profiles. Acetylene-Ar aggregates are also formed at the edge of the circular nozzle expansion cone. © 2008 Elsevier B.V. All rights reserved.

Resolved Torsional Splittings in the ν18 and ν19- Bands of Propene

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Investigation of the shape of the R(0) absorption line in ν3, N2O recorded from an axisymmetric supersonic free jet expansion

The hydrodynamic structure of an axisymmetric supersonic expansion can be regarded as a series of concentric divergent cones, with decreasing particle densities as the cone angle increases. Different groups of molecules therefore contribute to high-resolution absorption line shapes when optically probing the expansion in a direction perpendicular to the jet axis. These groups are distinguished by the cone angle, inducing a specific Doppler shift, and by the particle density, contributing a specific weight to the absorption intensity. As a result different broader line profiles are observed compared to room temperature spectra. This effect is investigated here selecting as the working example the R(0), ν3 absorption line in N2O recorded using a Fourier transform interferometer. Independent impact pressure and quadrupole mass spectrometric measurements are performed leading to two complementary maps of the expansion, allowing the recorded absorption line shape to be quantitatively modeled. © 2006 Elsevier Ltd. All rights reserved.

First High-Resolution Analysis of the Absorption Spectrum of Propane in the 6.7-7.5 μm Spectral Region

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Absolute line intensities for formic acid and dissociation constant of the dimer

Absolute line intensities in the v6 and v8 interacting bands of trans-HCOOH, observed near 1105.4 and 1033.5 cm -1, respectively, and the dissociation constant of the formic acid dimer (HCOOH)2 have been measured using Fourier transform spectroscopy at a resolution of 0.002 cm-1. Eleven spectra of formic acid, at 296.0(5) K and pressures ranging from 14.28(25) to 314.0(24) Pa, have been recorded between 600 and 1900 cm-1 with an absorption path length of 19.7(2) cm. 437 integrated absorption coefficients have been measured for 72 lines in the v6 band. Analysis of the pressure dependence yielded the dissociation constant of the formic acid dimer, k p=361(45) Pa, and the absolute intensity of the 72 lines of HCOOH. The accuracy of these results was carefully estimated. The absolute intensities of four lines of the weak v8 band were also measured. Using an appropriate theory, the integrated intensity of the v6 and v 8 bands was determined to be 3.47 × 1017 and 4.68 × 10-19 cm-1/(molecule cm-1) respectively, at 296 K. Both the dissociation constant and integrated intensities were compared to earlier measurements. © 2007 American Institute of Physics.

New high-resolution analysis of the ν7 and ν9 fundamental bands of trans-formic acid by IR Fourier transform and millimeterwave spectroscopies

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The HITRAN 2008 molecular spectroscopic database

This paper describes the status of the 2008 edition of the HITRAN molecular spectroscopic database. The new edition is the first official public release since the 2004 edition, although a number of crucial updates had been made available online since 2004. The HITRAN compilation consists of several components that serve as input for radiative-transfer calculation codes: individual line parameters for the microwave through visible spectra of molecules in the gas phase; absorption cross-sections for molecules having dense spectral features, i.e. spectra in which the individual lines are not resolved; individual line parameters and absorption cross-sections for bands in the ultraviolet; refractive indices of aerosols, tables and files of general properties associated with the database; and database management software. The line-by-line portion of the database contains spectroscopic parameters for 42 molecules including many of their isotopologues. © 2009 Elsevier Ltd.

Laboratory Fourier transform spectroscopy of the water absorption continuum from 2500 to 22500 cm-1

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