Atlas of high resolution infrared spectra of carbon dioxide Curtis P. Rinsland, D. Chris Benner, V. Malathy Devi, Penelope S. Ferry, Carolyn H. Sutton, and Donald J. Richardson

Curtis Rinsland is with NASA Langley Research Center, Atmospheric Sciences Division, Hampton, Virginia 23665; D. C. Benner, V, M Devi, and P. S. Ferry are with College of William and Mary, Physics Department, Williamsburg, Virginia 23185; the other authors are with Systems & Applied Sciences Corporation, Hampton, Vir­ginia 23665. Received 14 April 1984.

We are compiling an atlas of long-path low-pressure (<10 Torr) infrared laboratory absorption spectra of carbon diox­ide. The spectral data were recorded at 0.01-cm-1 resolution and room temperature with the Fourier transform spec­trometer in the McMath solar telescope complex of the Na­tional Solar Observatory at Kitt Peak. The latest edition1

contains 3336 lines in the 1830-2100-, 2395-2680-, and 3140-3235-cm-1 spectral regions, of which 94% have been identified as lines of carbon dioxide or as residual lines of H2O or CO. A total of 52 bands of 12C16O2, 13C16O2, 12C16O18O, 12C16O17O, and 13C16O18O have been assigned.

A typical frame of the atlas is shown in Fig. 1. Each frame contains a 1-, 2-, or 5-cm-1 interval of one or two spectra, de­pending on the complexity of the region. The facing page

contains the observed and calculated line positions and the molecular identifications. Each frame also contains a 0.2-cm - 1 overlap with the adjacent frames at the high and low wave number ends. The instrumental zero signal levels are marked at the lower left. The locations of the observed spectral lines are indicated below the features by vertical tick marks, which are repeated and numbered consecutively at the top of each frame.

Each observed line position is the weighted average of measurements obtained from one to six spectra. For isolated lines, the precision of the measured positions is typically ±0.00002 cm - 1 for the strongest lines and ±0.001 cm"1 for most weak lines. The absolute calibration of the wave num­ber scale is based on the frequency of the 3.39-μm P(7) tran­sition of CH4.2 The weakest lines in the atlas have absolute intensities of 0.5 X 10 -26 cm-1/molecule cm -2 at room temperature.

For many lines, the positions reported in the atlas are more accurate than the values listed in the current Air Force Geo­physics Laboratory (AFGL) line parameters compilation.3

Also, the analysis has led to the identification of nine bands which need to be added to the next update of this compilation. In AFGL notation, these new bands include the (21102) (10002) band of 12C16O2 and the (12201) (01101) band of 13C16O2 which have prominent lines in the 2050-cm-1 region and the (03301) (00001) forbidden band of 12C16O2 which is detectable because of l = 2 Fermi interactions between the (03301) upper level and the nearby (11101) and (11102) levels.

The positions and the relative intensities of the assigned and unassigned lines in the atlas spectra should be useful for analysis of data from atmospheric remote sensing experi­ments. These spectra also contain information on the abso­lute intensities of the CO2 lines. Results for the strongest

Fig. 1. The 2074-2076-cm-1 frame from the CO2 atlas.

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band near 5.2 μm have been reported,4 and work on the analysis of the intensities of other bands is in progress.

Additional spectral regions will be included in future updates to the CO2 atlas. A copy of the current version may be obtained by writing to the authors.

Research at the College of William and Mary and at Sys­tems & Applied Sciences Corp. is supported by grants from NASA. The National Solar Observatory is operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation. The authors thank M. A. H. Smith of NASA Langley Research Center and L. R. Brown of the Jet Propulsion Laboratory (JPL) for helpful discussions during the planning of the experiment, R. A. Toth of JPL for valuable suggestions on data analysis, and J. W. Brault of the National Solar Observatory for assistance in acquiring the data.

References 1. C. P. Rinsland, D. C. Benner, V. Malathy Devi, P. S. Ferry, C. H.

Sutton, and D. J. Richardson, NASA Technical Memorandum 85764 (NASA Langley Research Center, Hampton, Va., 1984), 467 pp.

2. K. M. Evenson, J. S. Wells, F. R. Petersen, B. L. Danielson, and G. W. Day, "Accurate Frequencies of Molecular Transitions Used in Laser Stabilization: the 3.39-μm Transition in CH4 and the 9.38- and 10.18-μm Transitions in Co29," Appl. Phys. Lett. 22, 192 (1973).

3. L. S. Rothman, R. R. Gamache, A. Barbe, A. Goldman, J. R. Gillis, L. R. Brown, R. A. Toth, J.-M. Flaud, and C. Camy-Peyret, "AFGL Atmospheric Absorption Line Parameters Compilation: 1982 Edition," Appl. Opt. 22, 2247 (1983).

4. C. P. Rinsland, D. C. Benner, D. J. Richardson, and R. A. Toth, "Absolute Intensity Measurements of the (1110)II 00°0 Band of 12C16O2 at 5.2 μm," Appl. Opt. 22, 3805 (1983).

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