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Title: Pressure broadening calculations for OH in collisions with argon: Rotational, vibrational, and electronic transitions

Authors:
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1413050
Grant/Contract Number:
DESC0002323
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Quantitative Spectroscopy and Radiative Transfer
Additional Journal Information:
Journal Volume: 189; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-12-12 16:37:12; Journal ID: ISSN 0022-4073
Publisher:
Elsevier
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Dagdigian, Paul J. Pressure broadening calculations for OH in collisions with argon: Rotational, vibrational, and electronic transitions. United Kingdom: N. p., 2017. Web. doi:10.1016/j.jqsrt.2016.11.013.
Dagdigian, Paul J. Pressure broadening calculations for OH in collisions with argon: Rotational, vibrational, and electronic transitions. United Kingdom. doi:10.1016/j.jqsrt.2016.11.013.
Dagdigian, Paul J. Wed . "Pressure broadening calculations for OH in collisions with argon: Rotational, vibrational, and electronic transitions". United Kingdom. doi:10.1016/j.jqsrt.2016.11.013.
@article{osti_1413050,
title = {Pressure broadening calculations for OH in collisions with argon: Rotational, vibrational, and electronic transitions},
author = {Dagdigian, Paul J.},
abstractNote = {},
doi = {10.1016/j.jqsrt.2016.11.013},
journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
number = C,
volume = 189,
place = {United Kingdom},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jqsrt.2016.11.013

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  • To understand the mechanism of pressure broadening one must have accurate values of the pressure broadening coefficients as a function of vibrational quantum number. Unfortunately, such data for polyatomic molecules are scarce. The coefficient for self-broadening of methane has been found to be the same for the R(0) and R(1) lines of the 2{nu}{sub 3} and 3{nu}{sub 3} bands and for an unidentified line of the 5{nu}{sub 1} + {nu}{sub 3} band at 6190 {angstrom} (1). Measurements have also been performed on the {nu}{sub 2} (2) and {nu}{sub 1} + {nu}{sub 3} (3) bands of acetylene. In the work describedmore » here, high resolution spectra of single vibrational-rotational lines of the 5{nu}{sub 3} band of acetylene at 15,600 cm{sup -1} have been taken to determine the coefficients for self-broadening at a much higher level of vibrational excitation. A single frequency cw dye laser (Spectra-Physics 580A) with Rhodamine B as the lasing medium is used as a narrow bandwidth light source. The laser is continuously scannable over a 10 GHz region with 30 MHz linewidth. The unfocused beam is chopped and directed through a small, nonresonant optoacoustic cell. The pressure of the acetylene (> 99.99% purity) in the cell is measured with a capacitance manometer. The optoacoustic signal is detected by a miniature electret microphone placed within the cell and is processed by a lock-in amplifier. The high resolution scans are calibrated ({+-} 5%) by monitoring the dye laser output with a spectrum analyzer equipped with 2 GHz FSR mirrors. All spectra were taken at room temperature (293 {+-} 2 K). At the relatively low pressures used in these experiments, the experimental linewidths are not more than three times the Doppler width (1.1 GHz FWHM). The method of Gronwall was used to calculate values of the Voigt lineshape. With these data, the pressure broadened widths, {Delta}{nu}{sub p}, were extracted from the experimental lineshapes and are plotted as a function of pressure for the R(3), R(9), and R(15) lines in Figure 1. The lines drawn through the data points were determined by the linear least squares method. The self-broadening coefficients, {gamma}, and their standard errors are summarized in Table 1 along with the results of other workers.« less
  • Using high-resolution laser spectroscopy of single vibrational-rotational lines of the 5 ..nu../sub 3/ band at 15,600 cm/sup -1/, the coefficient (..gamma..) for self-broadening for vibrational-rotational transitions of acetylene at a higher level of vibrational excitation were determined. The values obtained for ..gamma..'s and their standard errors are tabulated and compared with values obtained by other workers. The coefficient for self-broadening was found to be independent of vibrational excitation over a range of 2000 to 15,600 cm/sup -1/. (BLM)
  • The problem of vibrationally and rotationally inelastic scattering processes in H/sub 2/ + Ar for nonzero impact parameter b was investigated in the collision velocity range of 10/sup / to 10/sup 7/ cm/sec by use of the sudden approximation. The simultaneous vibrational (0 yields 1) and rotational (00 yields 00, 20, or 40) transitions were studied. For nu 3 x 10/sup 6/ cm/sec, the probabilities for b/l = 1.0 are found to be very large compared with those for b = 0, where l is the hardsphere collision diameter; for b/l > 1.0, the probabilities decrease very rapidly with increasingmore » b. The results show that nonzero-b collisions must be included in the calculation of simultaneous transition processes in H/sub 2/ + Ar at higher collision velocities. (auth)« less
  • Two new semiclassical methods: the multistate orbital treatment and the multichannel eikonal treatment: are proposed for the description of rotational and vibrational excitation in heavy-particle collisions. The first method includes appropriate trajectories determined from a certain optical potential designed to couple the response of the internal structure, which is described by a quantal multistate expansion, to the orbit for the relative motion and vice versa. While this approach is, in general, valid when the quantal imprecision in the classical trajectories is small (as for heavy particles) the second method based on the use of a straight-line eikonal for the relativemore » motion, of different local momenta in the various channels and of a multistate expansion for the internal motions, is valid for scattering mainly about the forward direction. These procedures are applied to representative rotational transitions in H--H$sub 2$ and He--H$sub 2$ collisions at 0.25--1.5 eV and yield angular distributions and integral cross sections in very close accord with corresponding quantal results. The methods are particularly valuable at higher impact energies when the inclusion of the resulting many rotational and vibrational channels by full quantal treatments is prohibitively difficult. Various approximate schemes--the perturbed-rotating-atoms approximation and the effective potential method-- are also investigated. (AIP)« less