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

Curtis P. Rinsland, Aaron Goldman, Mary Ann H. Smith, and V. Malathy Devi

Curtis P. Rinsland,^{3} Aaron Goldman,^{1} Mary Ann H. Smith,^{3} and V. Malathy Devi^{2}

^{1}University of Denver, Physics Department, Denver, Colorado 80208 USA

^{2}College of William and Mary, Physics Department, Williamsburg, Virginia 23185 USA

^{3}The other authors are with NASA Langley Research Center, Atmospheric Sciences Division, Chemistry & Dynamics Branch, Hampton, Virginia 23665-5225. USA

Curtis P. Rinsland, Aaron Goldman, Mary Ann H. Smith, and V. Malathy Devi, "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," Appl. Opt. 30, 1427-1438 (1991)

Lorentz air-broadening coefficients and relative intensities have been measured for forty-three lines in the pure rotational band and twenty lines in the ν_{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.

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Measured Lorentz Air-Broadening Coefficients
${b}_{L}^{0}\left({\mathrm{H}}_{2}\mathrm{O}-\text{air}\right)$ and Intensities in the Pure Rotational and ν_{2} Bands of H_{2}^{16}O from this Work Compare with the 1986 HITRAN Compilation Values14 and the Calculations of Benedict and Calfee15

Relative errors in the multiplicative scale factors used to calibrate the intensities from the various spectra

1

3.

Errors in calculating the overlapping absorption by nearby absorption lines

<3

The symbols S, W, and E″ have the following meaning:

S = error estimate for a strong line (intensity > l×10^{−23} cm^{−1}/molecule cm^{−2} at 296 K).

W = error estimate for a weak line (intensity < 5×10^{−25} cm^{−1}/molecule cm^{−2} at 296 K).

E″ = lower state energy of the transition in cm^{−1}.

Table IV

Comparison of Air-Broadening Coefficients from this Study and Values Inferred from the Published N_{2}-Broadening Coefficients of Eng and Mantz13 and the Calculated N_{2}-Broadening Coefficients of Tejwani16

Position (cm^{−1})

Transition

${\mathrm{b}}_{\mathrm{L}}^{0}\left({\mathrm{H}}_{2}\mathrm{O}-\text{air}\right)$ (cm^{−1} atm^{−1} at 296 K)

Derived from measured room-temperature N_{2}-broadened Lorentz coefficients (listed in Table I of Ref. 13) converted to air-broadened Lorentz coefficients at 296 K assuming Eqs. 1 and 3.
Derived from N_{2}-broadened Lorentz coefficients at 296 K calculated with a modified version of Anderson-Tsao-Curnutte theory including dipole-quadrupole and quadrupole-quadrupole interactions.16Eq. 3 of this paper was used to convert the N_{2}-broadened to air-broadened Lorentz coefficients.

Table V

Comparison of Line Intensities Measured by Saeidy12 and Eng and Mantz13 with the Values Measured In this Study

B = band code, 1 = pure rotation band, 2 = ν_{2} band.

Intensities are expressed in cm^{−1}/molecule cm^{−2} at 296 K.

Percent difference calculated as 100 × (Previous-This Study)/This Study.

In converting the Eng and Mantz intensities13 to the reference temperature of 296 K, we noticed a discrepancy between our computed temperature conversion and the conversions reported by Eng and Mantz.13 For example, in their Table IV Eng and Mantz13 report a correction factor of 3.924 in converting the intensity of the 1014.475-cm^{−1} H_{2}O line from 301.4 K to 383 K whereas we derive a factor of 3.847. The equations we assumed in converting the line intensities from one temperature to another are given in Eqs. 1 to 3 of Ref. 45.

Tables (5)

Table I

Measured Lorentz Air-Broadening Coefficients
${b}_{L}^{0}\left({\mathrm{H}}_{2}\mathrm{O}-\text{air}\right)$ and Intensities in the Pure Rotational and ν_{2} Bands of H_{2}^{16}O from this Work Compare with the 1986 HITRAN Compilation Values14 and the Calculations of Benedict and Calfee15

Relative errors in the multiplicative scale factors used to calibrate the intensities from the various spectra

1

3.

Errors in calculating the overlapping absorption by nearby absorption lines

<3

The symbols S, W, and E″ have the following meaning:

S = error estimate for a strong line (intensity > l×10^{−23} cm^{−1}/molecule cm^{−2} at 296 K).

W = error estimate for a weak line (intensity < 5×10^{−25} cm^{−1}/molecule cm^{−2} at 296 K).

E″ = lower state energy of the transition in cm^{−1}.

Table IV

Comparison of Air-Broadening Coefficients from this Study and Values Inferred from the Published N_{2}-Broadening Coefficients of Eng and Mantz13 and the Calculated N_{2}-Broadening Coefficients of Tejwani16

Position (cm^{−1})

Transition

${\mathrm{b}}_{\mathrm{L}}^{0}\left({\mathrm{H}}_{2}\mathrm{O}-\text{air}\right)$ (cm^{−1} atm^{−1} at 296 K)

Derived from measured room-temperature N_{2}-broadened Lorentz coefficients (listed in Table I of Ref. 13) converted to air-broadened Lorentz coefficients at 296 K assuming Eqs. 1 and 3.
Derived from N_{2}-broadened Lorentz coefficients at 296 K calculated with a modified version of Anderson-Tsao-Curnutte theory including dipole-quadrupole and quadrupole-quadrupole interactions.16Eq. 3 of this paper was used to convert the N_{2}-broadened to air-broadened Lorentz coefficients.

Table V

Comparison of Line Intensities Measured by Saeidy12 and Eng and Mantz13 with the Values Measured In this Study

B = band code, 1 = pure rotation band, 2 = ν_{2} band.

Intensities are expressed in cm^{−1}/molecule cm^{−2} at 296 K.

Percent difference calculated as 100 × (Previous-This Study)/This Study.

In converting the Eng and Mantz intensities13 to the reference temperature of 296 K, we noticed a discrepancy between our computed temperature conversion and the conversions reported by Eng and Mantz.13 For example, in their Table IV Eng and Mantz13 report a correction factor of 3.924 in converting the intensity of the 1014.475-cm^{−1} H_{2}O line from 301.4 K to 383 K whereas we derive a factor of 3.847. The equations we assumed in converting the line intensities from one temperature to another are given in Eqs. 1 to 3 of Ref. 45.