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
P. T. Spickler, C. P. Houck, J. A. Coakley, Kasie J.
Haga, Justin Dolph
Department of Physics, Bridgewater College,
Bridgewater, VA 22812
Adel and Slipher, Phys. Rev. 46, 902 (1934)
Problems with Band Models
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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
296K
Intensity (x10-24 cm/molecule)
150K
100K
40K
0
1
2
3
4
5
6
7
8
9
3.5
2.3
7.5
20.4
28.9
22.3
10.3
3.1
1.4
0.2
1.63
1.57
4.63
30.05
44.30
32.68
9.25
2.32
1.38
0.34
4.53
4.15
11.08
61.96
74.92
43.14
9.11
1.61
0.64
0.10
8.27
7.21
17.40
83.71
82.79
37.09
5.81
0.72
0.19
0.02
31.56
21.96
33.71
82.29
32.95
4.77
0.20
0.00
0.00
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