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Journal of Quantitative Spectroscopy &Radiative Transfer

Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–8

http://d0022-40

n CorrRAS, To

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journal homepage: www.elsevier.com/locate/jqsrt

Diode laser spectroscopy of H216O spectra broadened by N2

and He in 1.39 mm region

K.Yu. Osipov a,b,n, V.A. Kapitanov a, A.E. Protasevich a,A.A. Pereslavtseva c,d, Ya.Ya. Ponurovsky c

a V.E. Zuev Institute of Atmospheric Optics SB RAS, Tomsk, Russiab National Research Tomsk Polytechnic University, Tomsk, Russiac A.M. Prokhorov General Physics Institute of RAS, Moscow, Russiad Moscow Institute of Physics and Technology (State University), Moscow, Russia

a r t i c l e i n f o

Article history:Received 22 October 2013Received in revised form3 March 2014Accepted 5 March 2014Available online 15 March 2014

Keywords:Diode laserWater vaporSpectral line parametersMultispectrum fittingAtmospheric applications

x.doi.org/10.1016/j.jqsrt.2014.03.00373/& 2014 Elsevier Ltd. All rights reserved.

esponding author at: V.E. Zuev Institute of Amsk, Russia. Tel./fax: þ7 3822 492086.ail address: osipov@iao.ru (K.Yu. Osipov).

a b s t r a c t

Experimental spectra of pure water vapor and its mixtures with N2 and He were measuredin a pressure range (4–19 for pure H2O and 70–630 mBar for H2O diluted in N2 and Ne)by the diode laser spectrometer between 7184 and 7186 cm�1. The noise equivalentabsorption cross-section of the all observed spectra varied from 1.2 to 4.3�10–24 cm2/molec allowing signal to noise ratio from 10 for weak (intensity on the order of 5�10–25 cm/molec at 296 K) to 15,000 for strong (intensity on the order of 6�10–22 cm/molec) spectral lines respectively. The Voigt, Galatry, and Speed-dependent Voigt (SDV)profiles were used to fit the experimental spectra. This region includes 7 absorption linesof H2O and one HDO line according to the new line lists of H2O. Line positions, intensities,line shift, collisional broadening and narrowing coefficients for 6 spectral lines wereretrieved by multispectrum fitting procedure assuming the linear pressure dependence.The spectral parameters of the doublet (ν1þν3; 660’661; 661’660) at 7185.596 cm�1

were determined for the first time.& 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Water vapor is one of the key molecules in the atmo-sphere which plays an important role in the Earth'sclimate and weather changes. Knowledge of precise valuesof H2O spectral line parameters under various conditions isnecessary for a number of atmospheric applications, forexample, for calculation of solar radiation at the Earth'ssurface [1], for remote sensing of atmospheric watervapor concentration by the differential absorption methodetc. Diode lasers' infrared absorption spectroscopy is an

tmospheric Optics SB

efficient method for obtaining exact spectral line para-meters and for “in situ” measuring of water vapor con-centration in troposphere and lower stratosphere.The spectral interval ranging from 7165 to 7186 cm�1 isof interest for in situ monitoring of H2O in the atmosphereusing diode laser spectrometers [2,3].

Detailed information on the H2O line positions andintensities are presented in HITRAN [4] and water vaporspecial data banks [5–7]. Water vapor absorption spectrumin IR region contains a number of overlapping overtonesand combination bands, and such complex structure addsconsiderable difficulties for the spectra fitting in variousmixtures and for retrieval line profile parameters. Accord-ing to the theoretical treatments, the region under inves-tigation (from 7184 to 7186 cm�1) includes 7 stronglyoverlapping absorption lines of H2O and one of HDO with

K.Yu. Osipov et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–82

intensities higher than 10–25 cm/molec and line spacing upto 5�10�4 cm�1. Previous experimental studies in thisspectral region have been devoted to the retrieval of lineintensities and collisional broadening coefficients of onlyone [8,9], two [3,10] or four [7,11] lines.

In the present work we have recorded spectra of purewater vapor and in binary mixtures of water vapor with N2

and He in the spectral region from 7184 to 7186 cm�1 at abuffer gas pressure varying from 78 to 629 mBar. Applica-tion of the data obtained in previous works demonstratedthat the information on the spectral lines parameters isnot complete/precise in order to generate recorded spectrawith observation accuracy. The objective of present workis to obtain the spectral parameters of all lines located inthis region, especially, of the doublet (ν1þν3; 660’661;661’660) at 7185.596 cm�1. In contrast to the previousworks, the analysis of spectra has been carried out usingmultispectrum fitting procedure [12,13]. We used threemodels of the line profile: the Voigt, Galatry, and Speed-dependent Voigt (SDV) when fitting the spectra. All lineparameters were available for fitting and we took intoaccount the independence of the line position and inten-sity on the type of the buffer gas.

2. Experiment

Self-, He-, and N2-broadened spectra of water vaporwere recorded using experimental setup presented inFig. 1. The setup consists of two-channel diode laserspectrometer (DLS) and vacuum system for preparationof gas mixtures.

The pumping and wavelength tuning of DFB laser(NTT Electronics, λE1.392 μm) was provided by saw-tooth current pulses at repetition rate of 250 Hz and pulseduration of 3 ms. The wavelength in each pulse was tunedwithin the range Δν¼1.0�1.2 cm�1, depending on thesaw slope.

The laser crystal temperature was stabilized withaccuracy of 2�10�4 1C at temperature varying between

Diode laser Fibersplitter M

R

Fabry–

Pumping

Electronicsblock

Fig. 1. Diode laser spectrome

2 and þ55 1C. At an average magnitude of a pumpingcurrent of E60 mA the laser power was E15 mW and thelaser line half-width did not exceed 6 MHz.

The absolute calibration of the laser wavelength andits additional thermo-stabilization were made relative tothe position of pure water vapor absorption line in thereference cell at low pressure. Linearization of the spec-trum frequency scale was performed by recording a con-focal Fabry–Perot interferometer transmission (FSR¼0.04933 cm�1).

The DL radiation via optical fiber comes to fiber splitter.A small portion of laser radiation (E10%) passes to thereference cell, and the main part of the laser power(E90%) comes to the analytical cell. Recording of the laserintensities at the cell outputs was performed with InGaAsphotodetectors of Hamamatsu [http://jp.hamamatsu.com],with an active area diameter of 2 mm and a detectability(D*) of 5�1012 cm Hz1/2 W�1. The conversion factor andtransmission band of photodetector preamplifiers were10 V/mA and 120 kHz, respectively.

The water vapor mixtures were prepared inside thevacuum system, and then let into the analytical cell (∅¼30mm, L¼199.80±2 cm). Mixture pressure was managedwith the input vacuum valve and measured with “Elemer”AIR-20/M2 (measurement range 0–100 kPa with an error of0.2%) and “Sensor” (measurement range 0–10 kPa with anerror of 0.1%) sensors. The pressure signal was recorded by thespectrometer management system.

Under current experimental conditions the absorptioncross-section sðωÞ of gas sample can be derived from theBouger–Lambert–Beer law:

sðωÞ ¼ 1Ln

lnI0ðωÞIðωÞ

� �ð1Þ

where I0(ω) and I(ω) are the incident and transmittedlights respectively; L is the path length; n is the con-centration of absorbing molecules; and ω is the radiationwavenumber.

To decrease the influence of laser intensity fluctuationsand optical channel characteristics (possible reflections and

Photo-detector

Photo-detector

easurement cell

eference cell

P rot etalon

Gas mixturePressuremeter

NI-PCI 6251I/O board PC

ter experimental setup.

Fig. 2. Experimental spectra of pure H2O vapor at low pressure and itsdatabase [5,6] identification.

Table 1Spectral line parameters in the region under study.

ν, cm�1 S, cm/mol Isotope ν1ν2ν3 ν1ν2ν3 JKaKs JKaKs

7184.9844 6.301e�25 H2O 120 000 651 5427185.2422 4.442e�22 HDO 002 000 414 4237185.3944 5.391e�23 H2O 200 000 523 6167185.4005 9.671e�24 H2O 101 000 954 9557185.4430 3.822e�24 H2O 101 000 808 7257185.5771 2.257e�24 H2O 200 010 616 5237185.5961 2.002e�22 H2O 101 000 661 6607185.5966 6.002e�22 H2O 101 000 660 661

K.Yu. Osipov et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–8 3

absorptions by analytical cell windows) on measurements ofthe absorption cross-section, I0(ω) in (1) was determined asthe laser radiation intensity that passed the analytical cell inthe absence of the absorbing gas and was recorded only oncefor all measurements.

The Fabry–Perot etalon transmission was recorded andfrequency scale was linearized. Then the analytical cell wasfilled with the gas mixture at given pressure, and I(ω)was recorded. The sðωÞ was computed after accumulationand averaging of 20 I(ω) records. This method allowed toreach a relative error of r2�10�5 cm�1 in the frequencydetermination and the signal-to-noise ratio of Z104.

2.1. Line profile models

The line shape IðωÞ can be written as the real part of theFourier transform

IðωÞ ¼ 1πRe

Z 1

0e� iωtΦðtÞdt

� �ð2Þ

of the polarization correlation function ΦðtÞ, which for thespeed-dependent Voigt profile (SDVP) with a quadraticspeed dependence is given by [14]

ΦSDVPðtÞ ¼exp iω0tþ iðη0�3

2 η2Þt�ðγ0�32 γ2Þt

� �ð1þγ2t� iη2tÞ

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1þγ2t� iη2t

p�exp � ω0vat

2c

� �2 11þγ2t� iη2t

" #; ð3Þ

and for Galatry profile (GP) by [15]

ΦGPðtÞ ¼ exp iω0tþ iη0t�γ0t�ðω0va=cÞ2

2β2ðβt�1þe�βtÞ

" #:

ð4ÞIn Eqs. (3) and (4) ω0 is the line center frequency, γ0 and η0are the broadening and pressure shift parameters, respec-tively, c is the speed of light, and va is the most probablespeed of the absorbing molecule:

va ¼ffiffiffiffiffiffiffiffiffiffiffi2kBTm

r; ð5Þ

where kB is the Boltzmann constant, T is the gas tempera-ture, and m is the molecule's mass. The parameters γ2 andη2 in Eq. (3) describe the speed-dependence of the colli-sional width and shift, respectively. The parameter β inEq. (4) is the effective frequency of velocity-changingcollisions [16], which is related to the optical diffusioncoefficient D for the absorber in the perturbing gas as

β¼ kBTmD

:

The parameters γ0, γ2, η0, η2 and β are assumed to beproportional to pressure.

The polarization correlation function for usual Voigtprofile (VP) is

ΦVPðtÞ ¼ exp iω0tþ iη0t�γ0t�ω0vat2c

� �2" #

; ð6Þ

and can be easy obtained from Eq. (3), when setγ2 ¼ η2 ¼ 0, or from Eq. (3), when β-0.

3. Results

Fig. 2 shows the spectrum of pure water vapor underlow pressure (E5 mBar) and its line-intensity diagramaccording to [5].

According to Fig. 2 the recorded spectrum includes 5 wellresolved lines (four of H2O at 7184.984; 7185.395; 7185.443;7185.596 cm�1 and one of HDO at 7185.242 cm�1). Themeasured HDO line intensity is about 6�10–2671.77 cm/molec, in contrast to the corresponding value of about 4.442�10–22 cm/molec from [4]. Estimated value of the isotoperatio D/H is 135740 ppm. This value coincides with theNational Institute of Standards & Technology isotope ratioD/H¼155 ppm (Standard Mean Ocean Water) and D/H¼89.12 ppm (Standard Light Antarctic Precipitation) [17]. Beforeapplying multispectrum fitting procedure the HDO line wasexcluded from all recorded spectra.

Complete line list from Ref. [5] in this spectral region ispresented in Table 1. There are two unresolved line groupswith line spacing from 5�10�4 cm�1 (at 7185.596 cm�1) to61�10�4 cm�1 (at 7185.396 cm�1). Components whichwere included in a multispectrum fitting procedure are filledwith gray.

Our fitting procedure is based on the nonlinear least-square method. It derives the model parameters whichdescribe the experimental spectra at all applied pres-sures here with the minimum difference (experimentalminus simulated spectrum). The sets of pressures treated

Table 2Experimental pressure sets for multispectrum fitting procedure.

# Gas/mixture Pressures, mBar Total amount of spectra in multispectum fitting procedure

1 Pure H2O 4.23; 5.41; 7.08; 8.27; 9.59; 10.84; 12.35; 14.07; 16.23; 18.79. 102 H2O–N2 78; 121; 161; 215; 267; 309; 356; 410. 83 H2O–He 75; 107; 132; 174; 216; 267; 308; 356; 407; 469; 505; 544; 629. 13

K.Yu. Osipov et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–84

simultaneously in multispectrum fitting procedure areshown in Table 2

Fig. 3 shows the result of multispectum fitting as aresidual between experimental and simulated absorptioncross-sections spectra for some selected pressures.

The fitting of the experimental spectra using Voigtprofile gives the worst results. Table 3 presents the retrievedlines parameters using the Voigt profile. The data evidentlyshows that the use of Voigt profile and the multispectrumfitting procedure results in discrepancy of line centerpositions and intensities of the Ka doublet (ν1þν3; 660’661; 661’660) at 7185.596 cm�1 for different collisionalpartners. Moreover, one of the collisional broadening coef-ficients of the doublet has negative value.

While using more sophisticated line profiles, like theGalatry and SDVP, the residuals look almost similar andlead to significant reduction compared to the Voigt profile.

Table 4 presents the retrieved line center positions,intensities, pressure broadening, shift and collisional nar-rowing coefficients for 6 spectral lines of pure H2O and inbinary mixtures with He and N2 for Galatry profile. Table 5shows the same parameters for SDV profile.

4. Discussion

The high sensitive DL-spectrometer has allowed us tomeasure high quality experimental spectra with a signal-to-noise ratio from 10 for weak lines (intensity on theorder of 5�10–25 cm/molec at 296 K) to 15,000 for strongspectral lines (intensity on the order of 6�10–22 cm/molec). The present paper is devoted to the determinationof spectral parameters (line center positions, intensities,coefficients of broadening, shift, and collisional narrowing)for six lines of the main water vapor isotope. Theoreticalwork [5], which introduces the intensities and wavenum-bers of seven H2

16O lines and one HDO line, was used as abasis for processing the experimental spectra. The spectralline related to the HDO was excluded from the processingdue to low concentration (of about 135 ppm). Spectralline of the main isotope H2

16O at 7158.5771 cm�1

(the616’523 transition of 2ν1 vibrational band) is a very weakdoublet at 7185.596 cm�1 (see Ref. [5]), and has not beenincluded to the processing. The multispectrum fittingprocedure [12] with a linear pressure dependency ofcollisional broadening, narrowing and shift was used toretrieve spectral lines parameters. All lines' parameterswere fitted at the multispectrum fitting procedure.

Self-broadening line parameters were fixed to zero duringfitting spectra of the binary mixtures H2OþHe and H2OþN2,because of relatively small water vapor amount in thesemixtures. Spectral line shape was simulated with the Voigt,

Galatry [15], and the speed-dependent Voigt profiles [14].Based on the work [11] we gave preference to the Galatryprofile (soft-collision model) as a model to account forcollisional narrowing of lineshape (Dicke effect), but not tothe Rautian–Sobelman profile. The Galatry model and thespeed-dependent Voigt line profile model were used fordescription of three lines with the highest intensity only (i.e.for the Ka doublet of two lines 660’661 and 661’660 ofν1þν3 vibrational band, and for the line 523’616 of 2ν1vibrational band). The Voigt profile was quite sufficient for thedescription of the other three lines at the observed signal-to-noise ratio. For all spectra the residuals do not exceed 0.5% ofabsorption cross-section at maximumwhen the Galatry or thespeed-dependent Voigt profiles are used. Voigt profile givessignificantly worse results.

While fitting the N2-broadened spectra using Galatryprofile, the variation domain of narrowing parameters waslimited to positive values. Otherwise the nonlinear least-squares fit converged to the negative collisional narrowingvalue for one of the doublet lines. The narrowing parametercomes to a zero value after such constrain (see Table 4). Thedoublet lines' intensity ratio and the lines' positions in thiscase differ significantly from the lines parameters derivedfrom fitting of the pure H2O and H2O–He mixture, as well asfrom parameters of the speed-dependent Voigt profilefitting presented in Table 5.

The comparison of intensities and line center positionsof four appropriate spectral lines of H2

16O from differentliterature data with our results is presented in Table 6. Linepositions and intensities do not depend on the type of thebuffer gas, so Table 6 shows the averaged over all buffergases values for SDV profile.

The comparison of collision broadening and narrowingcoefficients with the data from Refs. [11,18,19] for523’616 line of 2ν1 band (line at 7185.394 cm�1), ispresented in Tables 7 and 8 respectively. Table 7 is a partof Table 4, and Table 8 is a part of Table 2 from Ref. [11] inwhich our data were added. It should be noted thatcollisional narrowing coefficients for the Galatry profilediffer significantly from each other for different lines inpure water vapor and especially in H2O–N2 mixture (seeour full table with retrieved lines parameters). Moreover,the retrieved coefficients β0 presented in Table 8 do notmatch with the calculated dynamic friction coefficientsβ0Diff from Ref. [11].

In previous works the Ka doublet (660’661 and661’660 of ν1þν3 band) was considered as a single linewith total intensity of about (7.8670.11)�10–22 cm/molec[11] and (7.670.2)�10–22 cm/molec [7]. Meanwhile, the-oretically calculated line positions and intensities of doub-let lines 660’661 (strong) and 661’660 (weak) of ν1þν3vibrational band corresponding to [5] are 7185.5966 cm�1,

Fig. 3. Residuals in % of absorption cross-section at maximum: (a) pureH2O; (b) H2O:N2; (c) H2O:He. Lines colors: gray – Voigt; red – Galatry;green – SDV. (For interpretation of the references to color in this figure

Table 3The retrieved lines parameters using Voigt profile.

ν0, cm�1 S�10–22,cm/molec.

γ0/P,cm�1/atm

η0/P,cm�1/atm

H2O 7184.977(5) 0.006(1) 0.2(3) 0.0(4)7185.3928(4) 0.56(4) 0.46(1) 0.04(3)7185.404(4) 0.05(4) 0.4(1) �0.6(3)7185.4416(8) 0.038(1) 0.49(6) �0.05(8)

7185.59621(3) 6.0(2) 0.32(1) 0.026(2)7185.59721(8) 1.9(2) �0.03(2)!!! �0.021(5)

He 7184.98(1) 0.010(4) 0.05(4) �0.01(5)7185.392(2) 0.5(3) 0.033(5) 0.003(2)7185.398(7) 0.1(3) 0.02(2) 0.00(1)7185.441(2) 0.04(4) 0.032(7) 0.003(9)

7185.59655(3) 6.8(2) 0.0216(4) 0.00467(8)7185.5967(1) 1.2(2) 0.0010(9) 0.0050(3)

N2 7184.99(8) 0.04(4) 0.7(6) 0.0(7)7185.393(2) 0(1) 0.12(6) �0.02(6)7185.395(5) 0(1) 0.1(1) 0.01(4)7185.436(7) 0.03(1) 0.07(3) 0.02(5)

7185.59660(9) 0.4(1) 0.010(4) �0.0137(7)7185.59663(2) 7.5(1) 0.0548(8) �0.0128(2)

K.Yu. Osipov et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–8 5

7185.5961 cm�1, and 6.002�10–22 cm/molec, 2.002�10–22 cm/molec respectively. The use of the SDV profile andmultispectrum fitting procedure makes it possible to

legend, the reader is referred to the web version of this article.)

resolve the doublet lines and to retrieve their positionsand intensities (see Table 9).

5. Conclusion

The high quality absorption spectra of pure water vaporand its mixtures with N2 and He were measured between7184 and 7186 cm�1 in a wide pressure range, using thediode laser spectrometer.

The objective of this paper was to obtain the consistentset of spectral parameters located in this region lines withintensity more than 5�10–26 cm/molec for H2O–H2O,H2O–He and H2O–N2 mixtures. In contrast to all previousworks the line positions and intensities of the Ka doublet(ν1þν3; 660’661; 661’660) at 7185.596 cm�1 were thecenter of our attention. To solve this problem the Voigt,Galatry and SDV profiles were used while fitting experi-mental spectra.

The Voigt profile is extensively used in a number ofatmospheric applications and is quite sufficient fordescription of the lines at the experimental signal-to-noise ratio of about a few of hundreds. It is shown in anumber of publications devoted to the problem of spectralline profile [8–16] that the use of Voigt profile results insystematic inaccuracy of residuals and intensities even forisolated lines when the signal-to-noise ratio is much more.The region under investigation (from 7184 to 7186 cm�1)includes 7 strongly overlapping lines of H2O with inten-sities from 10–25 cm/molec to 6�10–22 cm/molec and linespacing up to 5�10�4 cm�1. The use of Voigt profile forthe retrieval of spectral lines parameters of such a spectralead to the discrepancies in positions and line intensitiesratio of strong (Ka doublet) lines for different collisionpartners. Moreover, Voigt profile also gives essential errorsfor line positions and intensities of Ka doublet neighborlines (523’616 of 2ν1 band, 954’955 and 808’725 ofν1þν3 band). That is the main reason why it is impossible

Table 4The retrieved lines parameters using Galatry profile.

ν0, cm�1 S�10–22, cm/molec. γ0/P, cm�1/atm η0/P, cm�1/atm βsoft/P, cm�1/atm

H2O 7184.977(2) 0.0050(4) 0.14(10) �0.02(16) –

7185.3921(3) 0.47(4) 0.498(8) �0.013(11) 0.18(3)7185.3985(8) 0.15(4) 0.32(3) �0.052(27) –

7185.4416(3) 0.0396(5) 0.54(2) �0.032(32) –

7185.59309(8) 1.79(6) 0.220(1) �0.088(2) 0.227(5)7185.59747(2) 6.07(6) 0.2104(5) 0.0424(9) 0.133(1)

He 7184.981(2) 0.0090(7) 0.040(7) �0.0054(82) –

7185.3920(3) 0.51(4) 0.0330(5) 0.0012(4) 0.012(2)7185.399(1) 0.12(4) 0.021(2) �0.0005(14) –

7185.4411(3) 0.0384(7) 0.028(1) 0.0035(14) –

7185.5925(1) 1.53(8) 0.0191(1) 0.0036(2) 0.0159(5)7185.59746(3) 6.52(8) 0.01797(2) 0.00507(4) 0.0127(1)

N2 7184.99(2) 0.041(10) 0.72(15) �0.01(17) –

7185.392(2) 0.43(25) 0.117(9) �0.018(14) 0.049(40)7185.398(4) 0.19(25) 0.079(24) 0.0092(71) –

7185.436(1) 0.032(3) 0.068(9) 0.024(1) –

7185.5856(6) 0.16(2) 0.029(2) 0.00156(1) 0.000(5)7185.59681(2) 7.78(2) 0.05376(8) �0.0127(1) 0.0276(2)

Table 5The retrieved lines parameters using SDV profile.

ν0, cm�1 S�10–22, cm/molec. γ0/P, cm�1/atm γ2/P, cm�1/atm η0/P, cm�1/atm

H2O 7184.977(2) 0.0052(4) 0.17(9) – �0.03(16)7185.3922(3) 0.48(4) 0.500(9) 0.061(9) �0.017(11)7185.3986(9) 0.14(4) 0.31(3) – �0.043(29)7185.4416(3) 0.0396(6) 0.54(2) – �0.036(32)

7185.59350(7) 2.13(7) 0.224(1) 0.073(2) �0.092(2)7185.59759(3) 5.72(7) 0.2096(5) 0.0471(5) 0.053(1)

He 7184.981(2) 0.0105(8) 0.053(8) – �0.0063(96)7185.3921(3) 0.52(3) 0.0332(6) 0.0042(6) 0.00061(50)7185.399(1) 0.12(3) 0.020(2) – 0.0009(15)

7185.4412(3) 0.0379(7) 0.026(1) – 0.0026(15)7185.5936(1) 2.1(1) 0.01860(7) 0.0051(1) 0.00082(18)

7185.59760(4) 5.9(1) 0.01841(3) 0.0045(1) 0.00620(4)

N2 7184.981(8) 0.0051(14) 0.07(3) – �0.022(47)7185.393(1) 0.47(27) 0.114(9) 0.0061(70) �0.016(14)7185.397(4) 0.15(27) 0.08(3) – 0.011(9)7185.439(2) 0.035(3) 0.077(10) – �0.015(11)

7185.59475(6) 2.0(1) 0.0530(8) 0.000010(13) �0.00328(8)7185.59723(6) 5.9(1) 0.054379 0.0101(3) �0.0159(3)

Table 6The comparison of intensities and line center positions of four appropriate spectral lines of H2

16O from different literature data with results from thecurrent work.

ω0, cm�1

S�10–22, cm/molec.

Toth [7] This worka Lepère et al. [11] Toth [7] Lesh et al. [5] This worka

7184.964 7184.980(2) – 0.005670.0002 0.006301 0.0069(4)7185.394 7185.3924(5) 0.52870.023 0.4470.04 0.5391 0.49(5)7185.400 7185.398(2) 0.11570.011 0.1070.02 0.09671 0.14(3)7185.442 7185.4407(8) 0.041270.0023 0.04270.006 0.03822 0.0375(6)

a The averaged over all buffer gases values for SDV profile. The uncertainties correspond to one standard deviation, obtained by averaging of differentmeasurements.

K.Yu. Osipov et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–86

to retrieve the consistent set of the line positions andintensities located in this region lines for Voigt profile.

Galatry profile is more appropriate than Voigt to describeour experimental spectra with acceptable accuracy. But the

set of spectral parameters of the lines belonging to the Kadoublet is not consistent. So for H2O–N2 mixture the linecenter positions and intensities of the Ka doublet linesare retrieved incorrectly. They disagree with the same

Table 8Collision narrowing coefficients for H2O line at 7185.394 cm�1 formixtures with He and N2 (in cm�1/atm), and comparison with dynamicfriction coefficients.

Gasmixtures

β0, cm�1/atm β0Diff, cm�1/atm

This work(Galatry)

Lepère et al.[11]

Lepère et al.[11]

H2OþHe 0.012(2) 0.00870.003 0.008H2OþN2 0.049(40) 0.03270.011 0.031

The uncertainties correspond to one standard deviation obtained byaveraging different measurements (except our work).

Table 9Comparison of line positions and intensities for Ka doublet.

ω0, cm�1 S�10–22, cm/molec.

Lesh et al. [5] This worka Lesh et al. [5] This worka

7185.5961 7185.5940(2) 2.002e�22 2.1(1)7185.5966 7185.5975(2) 6.002e�22 5.84(9)

a The averaged over buffer gases values for SDV profile.

Table 7Collision broadening coefficients for H2O line at 7185.394 cm�1 for the pure H2O and in mixture with He and N2 (in cm�1/atm).

Gas mixtures γ0, cm�1/atm

This work (Galatry) This work (SDV) Lepère et al. [11] Nagali et al. [19] Delaye et al. [18]

H2OþH2O 0.498(8) 0.500(9) 0.434970.0094 0.27070.025 0.395H2OþHe 0.0330(5) 0.0332(6) 0.021170.0013 – –

H2OþN2 0.117(9) 0.114(9) 0.093970.0027 0.10370.016 0.091

The uncertainties correspond to one standard deviation obtained by averaging different measurements (except our work).

K.Yu. Osipov et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 142 (2014) 1–8 7

parameters retrieved from H2O–H2O and H2O–He mixtures(see Table 4). The collisional narrowing coefficients for theGalatry profile differ significantly from each other for differ-ent lines in pure water vapor and especially in H2O–N2

mixture. Moreover, the retrieved coefficients do not matchwith the calculated dynamic friction coefficients β0Diff fromRef. [11]. Thus the Galatry profile is also unable to providereliable set of line parameters.

The usage of the SDV profile allows describing thewhole set of our experimental spectra with the sufficientaccuracy of spectral line parameters (see Table 5). The SDVprofile and multispectrum fitting procedure allowed us toresolve the Ka doublet for the first time. Line positions,intensities, line shift, collisional broadening for 6 spectrallines and narrowing coefficients for 3 strong lines wereretrieved using multispectrum fitting procedure andassuming linear pressure dependence. For the all recordedspectra the residuals do not exceed 0.5% of absorptioncross-section at maximum, when the SDV profile was usedfor the description of the lines at signal-to-noise ratio ofabout a few of thousands.

Acknowledgments

This work is partly supported by the Project VIII 80.1.1SB RAS and by the Program III.9 of RAS Physical Division.The authors are grateful to Dr. Yu.N. Ponomarev, Dr. I.V.Ptashnik and Dr. A.I. Nadejdinsky for useful discussion andrecommendations.

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