Mary Ann H. Smith

The HITRAN database - 1986 edition

A description and summary of the latest edition of the AFGL HITRAN molecular absorption parameters database are presented. This new database combines the information for the seven principal atmospheric absorbers and twenty-one additional molecular species previously contained on the AFGL atmospheric absorption line parameter compilation and on the trace gas compilation. In addition to updating the parameters on earlier editions of the compilation, new parameters have been added to this edition such as the self-broadened halfwidth, the temperature dependence of the air-broadened halfwidth, and the transition probability. The database contains 348043 entries between 0 and 17,900 cm(-1). A FORTRAN program is now furnished to allow rapid access to the molecular transitions and for the creation of customized output. A separate file of molecular cross sections of eleven heavy molecular species, applicable for qualitative simulation of transmission and emission in the atmosphere, has also been provided.

A MULTISPECTRUM NONLINEAR LEAST SQUARES FITTING TECHNIQUE

Abstract An extension of the nonlinear least squares spectrum fitting technique has been developed for the simultaneous fitting of multiple spectra. This procedures smaller number of fitted parameters as compared to fitting one spectrum at a time improves the determination of spectroscopic parameters. A more reliable evaluation of the errors associated with the solution is possible. Correlations among fitted parameters may preclude their determination from a single spectrum fit. If the correlations differ from spectrum to spectrum, however, separation of these parameters is often possible when including the spectra in one solution. Overfilling is also avoided when combining spectra with sufficiently different experimental physical conditions.

Methane line parameters in HITRAN

Abstract Two editions of the methane line parameters (line positions, intensities and broadening coefficients) available from HITRAN in 2000 and 2001 are described. In both versions, the spectral interval covered was the same (from 0.01 to 6184.5 cm −1 ), but the database increased from 48,033 transitions in 2000 to 211,465 lines in 2001 because weaker transitions of 12 CH 4 and new bands of 13 CH 4 and CH3D were included. The newer list became available in 2001 in the “Update” section of HITRAN. The sources of information are described, and the prospects for future improvements are discussed.

Measurements of Lorentz air-broadening coefficients and relative intensities in the H 2 16 O pure rotational and ν 2 bands from long horizontal path atmospheric spectra

Lorentz air-broadening coefficients and relative intensities have been measured for forty-three lines in the pure rotational band and twenty lines in the v(2) band of H(2)(16)O between 800 and 1150 cm(-1). The results were derived from analysis of nine 0.017-cm(-1) resolution atmospheric absorption spectra recorded over horizontal paths of 0.5-1.5 km with the McMath Fourier transform spectrometer and main solar telescope operated on Kitt Peak by the National Solar Observatory. A nonlinear least-squares spectral fitting technique was used in the spectral analysis. The results are compared with previous measurements and calculations. In most cases, the measured pressure-broadening coefficients and intensities are significantly different from the values in the 1986 HITRAN line parameters compilation.

Stratospheric N 2 O mixing ratio profile from high-resolution balloon-borne solar absorption spectra and laboratory spectra near 1880 cm −1

A nonlinear least-squares fitting procedure has been used to derive the stratospheric N(2)O mixing ratio profile from balloon-borne solar absorption spectra and laboratory spectra near 1880 cm(-1). The atmospheric spectra were recorded during sunset from a float altitude of 33 km with the University of Denver 0.02-cm(-1) resolution interferometer near Alamogordo, N.M. (33 degrees N), on 10 Oct. 1979. The laboratory data were used to determine the N(2)O line intensities. The measurements indicate an N(2)O mixing ratio of 264 ppbv near 15 km decreasing to 155 ppbv near 28 km.

The ν1 and ν3 bands of 16O18O16O: line positions and intensities

Abstract Room temperature absorption spectra of 18 O-enriched ozone have been recorded around 10 μm using a high-resolution Fourier transform spectrometer. The ν 1 and ν 3 bands of 16 O 18 O 16 O have been extensively analyzed, leading to the determination of precise vibrational energies and rotational and coupling constants. The following band centers were derived: ν 1 = 1074.30756 ± 0.00041 cm −1 and ν 3 = 1008.45277 ± 0.00015 cm −1 . The line intensities were calculated transferring the dipole moment function of 16 O 3 to 16 O 18 O 16 O, and finally a complete list of line positions and intensities of the ν 1 and ν 3 bands of 16 O 18 O 16 O has been generated.

Measurements of 12 CH 4 ν 4 band halfwidths using a tunable diode laser system and a Fourier transform spectrometer

Air-broadened and N2-broadened halfwidths at room temperature for twenty-five transitions in the ν4 fundamental band of 12CH4 have been determined from IR absorption spectra recorded with a tunable diode laser spectrometer. Two tunable diode lasers operating in the 1250–1380-cm−1 region were used to obtain these data. Air-broadened halfwidths for twenty of these lines were also determined from additional spectra recorded at 0.01-cm−1 resolution with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak. The air-broadened halfwidths obtained from these two techniques are very consistent with agreement better than 3% in most cases.

Diode laser measurements of air and nitrogen broadening in the ν2 bands of HDO, H216O, and H218O

Abstract Pressure-broadening coefficients for several rotation-vibration lines in the ν 2 bands of HDO, H 2 16 O, and H 2 18 O have been determined from laboratory spectra recorded in the 1260- to 1360-cm −1 region with a tunable diode laser spectrometer system. Air and nitrogen were used as the broadening gases and, for all the measured transitions, the nitrogen-broadened half-widths were found to be consistently larger than the corresponding air-broadened half-widths by about 12%. The results have been compared to previously published values when appropriate.

Self- and N2-broadening, pressure induced shift and line mixing in the ν5 band of 12CH3D using a multispectrum fitting technique

Abstract We report the first measured Lorentz self- and nitrogen-broadening and the corresponding pressure-shift coefficients in the ν5(E) perpendicular band of 12CH3D between 1275 and 1600 cm −1 . The multispectrum fitting technique allowed us to analyze simultaneously both self-broadened and N2-broadened spectra recorded at 0.005 to 0.006-cm−1 resolution with a Fourier transform spectrometer located at Kitt Peak. Self-broadening coefficients for over 550 transitions and self-shift coefficients for more than 480 transitions with rotational quantum numbers up to J″=17 and K″=14 were determined. Nitrogen-broadening and nitrogen pressure-induced shift coefficients were determined for more than 300 of those transitions. The measured broadening coefficients vary from 0.020 to about 0.091 cm −1 atm −1 at 296 K . The measured pressure-shift coefficients had values extending from about −0.014 to +0.005 cm −1 atm −1 . Very few of the pressure-shift coefficients were positive, and the positive pressure-shift coefficients were mostly associated with the J″=K″ transitions in the PQ sub-bands. The J″=K″ transitions in the PP and RR sub-bands were associated with the smallest broadening coefficients. Our measurements also included 46 forbidden lines with Δ K=±2 (10 O P , 9 O Q ,3 Q P , 7 Q Q , 1 Q R , 13 S Q and 3 SR). The off-diagonal relaxation matrix element coefficients, Wij, in cm −1 atm −1 at 296 K which are associated with line mixing were determined for a few transitions with K″=3 (A+A−splitting) in the P P , P Q and RP sub-bands. We have examined the dependence of the measured parameters on J,K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of J and K.

Multispectrum analysis of pressure broadening and pressure shift coefficients in the 12C16O2 and 13C16O2 laser bands

Abstract Extensive high-resolution experimental determination is provided for air- and N2-broadening and pressure shift coefficients for the two 13 C 16 O 2 laser bands (located at 913.4 and 1017.6 cm −1 , respectively), in addition to new measurements of self-broadening and self-shift coefficients for the 12 C 16 O 2 laser bands. These parameters were determined from analysis of spectra recorded with the McMath–Pierce Fourier transform spectrometer (FTS) of the National Solar Observatory on Kitt Peak, Arizona. We used a multispectrum nonlinear least-squares fitting technique to analyze 30 long path, room temperature absorption spectra. By combining the spectra of 12 CO 2 and 13 CO 2 in the same fit we were able to obtain a consistent set of line parameters for both molecules. The results obtained for the 12 CO 2 and 13 CO 2 laser bands were compared with each other, with values in the HITRAN database, and with values reported in the literature for CO2 bands. Comparisons revealed no significant differences in the broadening or shift coefficients between the two laser bands. The coefficients determined for the two isotopomers agreed closely.