FOURIER TRANSFORM RAMAN SPECTROSCOPY OF $H_{2}$ AND $D_{2}$ IN FLAMES
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Date
1985
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Ohio State University
Abstract
Laboratory spectra of high rotational transitions in $H_{2}$ are important in astrophysics because they may be observable in hot stellar and interstellar sources, and have already been seen in quadrupole emission from the Orion molecular $cloud.^{1}$ The Orion emission lines are characteristic of an $\sim$ 2000K rotational temperature. Infrared spectra of $H_{2}$ and $D_{2}$ at high temperatures are difficult to obtain in the laboratory because path lengths of hundreds of meters are necessary to observe the quadrupole absorption. Vibration-rotation coefficients obtained from room temperature spectra cannot be extrapolated to the high-J lines observed in Orion to within the accuracies of the astronomical measurements. Prompted by these considerations, we have recorded Raman spectra of high temperature molecular hydrogen and deuterium using a Fourier transform spectrometer. A diffusion flame source burning $H_{2}$ or $D_{2}$ in air was placed at the focal point of a multi-pass $cell.^{2}$ Raman scattering of argon-ion laser light was observed with the l-m Fourier transform spectrometer at Kitt $Peak.^{3}$ The observed pure-rotation spectra of $H_{2}$ and $D_{2}$, and the vibration-rotation spectra of $H_{2}$, contain transitions with higher rotational energy than had been possible to observe previously at room temperature. The transitions in $H_{2}$ extended to J=9-7 and those in $D_{2}$ extended to J=12-10. The rotation-vibration coefficients will be re-examined taking the new transitions into account.
Description
$^{1}$R. F. Knacke and E. T. Young, Ap. J. (Letters) 249, L65 (1981). $^{2}$Cell provided by R. A. Hill. See R. A. Hill, A. J. Mulac, and C. E. Hackett, Appl. Opt. 16, 2004 (1977). $^{3}$The l-m FTS is a facility of the National Solar Observatory, National Optical Astronomy Observatories, operated by the Association of Universities for Research in Astronomy, Inc. under a grant from the National Science Foundation.
Author Institution: Planetary Systems Branch, Code 693, NASA/Goddard Space Flight Center; Planetary Systems Branch, National Bureau of Standards; Planetary Systems Branch, National Solar Observatory
Author Institution: Planetary Systems Branch, Code 693, NASA/Goddard Space Flight Center; Planetary Systems Branch, National Bureau of Standards; Planetary Systems Branch, National Solar Observatory