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The 4 3 Spectral Region of Methane. D. Chris Benner, V. Malathy Devi Department of Physics, College of William and Mary, Williamsburg, VA 23187-8795 J. J. O'Brien, S. Shaji Department of Chemistry and Biochemistry, University of Missouri - St. Louis, St. Louis, MO 63121-4400
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The 43 Spectral Region of Methane D. Chris Benner, V. Malathy Devi Department of Physics, College of William and Mary, Williamsburg, VA 23187-8795 J. J. O'Brien, S. Shaji Department of Chemistry and Biochemistry, University of Missouri - St. Louis, St. Louis, MO 63121-4400 P. T. Spickler, C. P. Houck, J. A. Coakley, Kasie J. Haga, Justin Dolph Department of Physics, Bridgewater College, Bridgewater, VA 22812
Problems with Band Models • Placement of spectral lines • Intensity distribution of spectral lines • T≠T1*T2 • Gas must be Isothermal • Gas must all be at the same Pressure • Almost all scattering models are excluded • Temperature dependence is simple at best • Band Models based upon planetary spectra instead of laboratory spectra
Distribution of Lower States • J” % of Lines Intensity (x10-24 cm/molecule) • 296K 150K 100K 40K • 0 3.5 1.63 4.53 8.27 31.56 • 1 2.3 1.57 4.15 7.21 21.96 • 2 7.5 4.63 11.08 17.40 33.71 • 3 20.4 30.05 61.96 83.71 82.29 • 4 28.9 44.30 74.92 82.79 32.95 • 5 22.3 32.68 43.14 37.09 4.77 • 6 10.3 9.25 9.11 5.81 0.20 • 7 3.1 2.32 1.61 0.72 0.00 • 8 1.4 1.38 0.64 0.19 0.00 • 9 0.2 0.34 0.10 0.02 0.00 • Total 100.0 128.14 211.24 243.21 207.44
Summary • Methane bands appear in the visible and near infrared of spectra outer solar system objects • These band systems are very complex interactions of many bands • At room temperatures the spectral lines overlap severely • At outer solar system temperatures and low pressure the spectrum is measurable with the multispectrum technique • A line list is being produced for the 890 nm band complex • This line list will make possible realistic modeling of outer solar system object – even including scattering