Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology...

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Yu. I. BARANOV, Yu. I. BARANOV, W. J. LAFFERTY, and G. T. W. J. LAFFERTY, and G. T. Fraser Fraser Optical Technology Division Optical Technology Division National Institute of Standards and National Institute of Standards and Technology, Technology, Gaithersburg, MD 20899-8441, USA Gaithersburg, MD 20899-8441, USA The water-vapor continuum and The water-vapor continuum and selective absorption in the 8 to 12 selective absorption in the 8 to 12 μm and 3 to 5 μm windows at μm and 3 to 5 μm windows at temperatures from 311 to 363K temperatures from 311 to 363K . .

Transcript of Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology...

Page 1: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Yu. I. BARANOV, Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser W. J. LAFFERTY, and G. T. Fraser

Optical Technology DivisionOptical Technology DivisionNational Institute of Standards and Technology,National Institute of Standards and Technology,

Gaithersburg, MD 20899-8441, USAGaithersburg, MD 20899-8441, USA

The water-vapor continuum and selective The water-vapor continuum and selective absorption in the 8 to 12 absorption in the 8 to 12 μm and 3 to 5 μm μm and 3 to 5 μm windows at temperatures from 311 to 363Kwindows at temperatures from 311 to 363K..

Page 2: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Introduction

The water vapor continuum absorption in the atmospheric 8 to 12 and 3 to 5 μm windows strongly affects the Earth’s outgoing and the Sun’s incoming radiation and therefore is of great importance for radiative balance calculations.

Page 3: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Introduction

Increasing use of lasers, spectrometers, and other IR techniques in atmospheric research, remote sensing, and environment protection also requires more precise data on water vapor continuum absorption coefficients

Page 4: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Introduction

Over the past twenty years many scientific groups in the world have used long-base (up to 100 m) long-path (up to several thousands m) cells to measure the H2O continuum.

Page 5: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Introduction

The other high-sensitive techniques, like photo-acoustic or cavity ring-down

spectroscopy (CRDS) have also been employed for these measurements.

Revised and selected data were put on the basis of the CKD(a) continuum model, widely used for atmospheric spectroscopy applications.

a S. A. Clough, F. X. Kneizys, and R. W. Davies, Atmos. Res. 23, 229-241 (1989).

Page 6: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Experimental set-up view

Page 7: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Experimental conditionsSpectral resolution is 0.1 cm-1

Spectral range 800 to 3500 cm-1

TemperatureK (±0.3K)

Pressure rangekPa (torr)

Path lengthm

Number of spectra

310.8 2.83 to 6.07 (21.2 to 45.5)

68-116 41

318.0 3.40 to 7.42 (25.5 to 55.7)

84-116 46

325.8 4.49 to 11.5 (33.7 to 86.3)

76-116 48

339.3 5.21 to 12.3 (39.1 to 92.0)

84-108 51

351.9 5.76 to 15.1 (43.2 to 113) 84-116 51

363.6 5.48 to 13.7 (41.1 to 103) 84-116 36

Page 8: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

An example of IR water vapor spectrum

0

0.2

0.4

0.6

0.8

1

800 900 1000 1100 1200 1300 1400

Tra

ns

mit

tan

ce

Continuum absorption

The v2 watervapor fundamental

band

0

0.2

0.4

0.6

0.8

1

1750 1950 2150 2350 2550 2750 2950

Wavenumber, cm-1

Tra

ns

mit

tan

ce

Res=0.1 cm-1

T=339.2KP=89.5 torrL=9205 cm

Page 9: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The small part of four spectra at different pressures

0.5

0.6

0.7

0.8

0.9

1

940 942 944 946 948 950

Wavenumber, cm-1

Tra

ns

mit

tan

ce

T=318KL=108mP, torr28.735.443.353.9

The quick data treatment methodMeasured absorbance versus

density square

0

1

2

3

4

0 0.005 0.01

Density, amagat2

(-ln

T/L

)*1

05,

cm

-1

318K326K339K

Page 10: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The basic data treatment method

0.2

0.4

0.6

0.8

1

800 900 1000 1100 1200 1300

Wavenumber, cm-1

Tra

ns

mit

tan

ce

0.4

0.6

0.8

1

1920 2020 2120 2220

Wavenumber, cm-1

Tra

ns

mit

tan

ce

Two spectra at:

Θ=318KL=116mP=51.2 torr

Θ=352KL=116mP=111.9 torr

Page 11: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The basic data treatment method

,,, structcontobs TTT ,

','',

dTfT linstruct

,25

,

,

,exp,

2222 P

P

P

PSPLT

ii

i

ii

i

i

ilin

Here f(ν-ν’) – instrumental function; L – a path length;

P, Θ – water vapor pressure, and temperature; Si, γi and νi – line parameters from the HITRAN data base; the sum is taken over all lines in a spectral range ν ± 25 cm-1

Page 12: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The basic data treatment method

0.2

0.4

0.6

0.8

1

800 900 1000 1100 1200 1300

Wavenumber, cm-1

Tra

ns

mit

tan

ce

0.4

0.6

0.8

1

1920 2020 2120 2220

Wavenumber, cm-1

Tra

ns

mit

tan

ce

Two spectra at:

Θ=318KL=116mP=51.2 torr

Θ=352KL=116mP=111.9 torr

Page 13: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The basic data treatment method

Two spectra at:

Θ=318KL=116mP=51.2 torr

Θ=352KL=116mP=111.9 torr

0.2

0.4

0.6

0.8

1

800 900 1000 1100 1200 1300

Wavenumber, cm-1

Tra

ns

mit

tan

ce

0.4

0.6

0.8

1

1920 2020 2120 2220

Wavenumber, cm-1

Tra

ns

mit

tan

ce

Page 14: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The basic data treatment method

0.2

0.4

0.6

0.8

1

800 900 1000 1100 1200 1300

Wavenumber, cm-1

Tra

ns

mit

tan

ce

0.4

0.6

0.8

1

1920 2020 2120 2220

Wavenumber, cm-1

Tra

ns

mit

tan

ce

2

1ln

ji

ij

ba

LT

jijT ,

Every data arrayfor a giventemperature Θ

was fittedby function:

using standardleast squaremethod.

Page 15: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Water vapor continuum binary absorptioncoefficients Cs in cm-1(mol/cm3)-1atm-1

compared with CKD model values

Wavenumber, cm-1

0.0E+00

5.0E-23

1.0E-22

1.5E-22

2.0E-22

2.5E-22

3.0E-22

3.5E-22

800 900 1000 1100 1200 1300 1920 2020 2120 2220 2320

The CKD values are shown as solid lines

310.8K325.8K351.9K

Page 16: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The temperature dependence of the continuum binary absorption coefficient at 942 cm-1

0

1

2

3

4

270 290 310 330 350 370 390

Temperature, K

Cs*

10

22, c

m-1

/(m

ole

c*c

m-3

)

Nordstrom et al.,1978, (CO2-laser, White cell)Peterson et al., 1979, (CO2-laser, White cell)Eng and Mantz, 1980, (diode laser, White cell)Burch et al., 1982, (spectrometer, White cell)Loper et al., 1983, (CO2-laser, spectrophone)Hinderling, 1987, (CO2-laser, spectrophone)Cormier et al., 2005, (CO2-laser, CRDS)NIST 2006, (spectrometer, White cell)Clough, CKD model

Page 17: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The temperature dependence of the continuum binary absorption coefficient at 1203 cm-1

0

0.3

0.6

0.9

1.2

1.5

290 340 390 440

Temperature, K

Cs*1

022 ,

cm

-1/(

mo

lec*c

m-3

)

Montgomery, 1978Burch et al., 1982NIST, 2006Clough CKD model

Page 18: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

The temperature dependence of the continuum binary absorption coefficient

1.00

1.50

2.00

2.50

3.00

3.50

2.40 2.60 2.80 3.00 3.20 3.40

ln(C

s*1

023)

850 cm-1

944 cm-1

1100 cm-1

1200 cm-1

The first and the last big figures arereproduced from AFGL-TR-81 (Burch D. E.)

0.30

0.80

1.30

1.80

2.30

2.80

3.30

2.60 2.80 3.00 3.20 3.40

ln(C

s*1

023)

1930 cm-1

1973 cm-1

2050 cm-1

2143 cm-1

Temperature, 1000/Θ, K-1 Temperature, 1000/Θ, K-1

Page 19: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wavenumber, cm-1

Cs,

cm

-1a

ma

ga

t-2

273K296K330K

The water vapor selfbroadened continuum (as it comes from the CKD programm)

The bottom line represents the distribution of the allowed transition intensities.

δν1/2=246 cm-1

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wavenumber, cm-1

Cs*

10

4 cm

-1 a

ma

ga

t-2

233K273K333K

230K270K346K

Ho, Birnbaum, Rosenberg,J. Chem. Phys., 55, 1028, 1971 NIST, 2003

CO2 roto-translational band and collision induced/dimer spectrum

δν1/2=72 cm-1

Page 20: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wavenumber, cm-1

Cs,

cm

-1a

ma

ga

t-2

273K296K330K

The water vapor selfbroadened continuum (as it comes from the CKD programm)

The bottom line represents the distribution of the allowed transition intensities.

δν1/2=246 cm-1

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wavenumber, cm-1

Cs*1

05, c

m-1

am

agat

-2

163K296K

Methane roto-translational band

Dore, Moraldi, Poll and BirnbaumMolec. Phys., 66, 363, 1989

δν1/2=311 cm-1

Page 21: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

0

1

2

3

4

5

0 200 400 600 800 1000

Wavenumber, cm-1

Cs*1

06, c

m-1

am

agat

-2

Bosomworth and Gush,Can. J. Phys. 43, 751, 1965

300K

δν1/2=111 cm-1

2000 2200 2400 2600 2800 3000

NIST, 2004300K

Pure nitrogen roto-translational band and CIA spectrum

0

0.04

0.08

0.12

0.16

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wavenumber, cm-1

Cs,

cm

-1a

ma

ga

t-2

296K

The N2-broadened continuum(as it comes from the CKD programm)

δν1/2=158 cm-1

Page 22: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wavenumber, cm-1

Cs,

cm

-1a

ma

ga

t-2

273K296K330K

The water vapor selfbroadened continuum (as it comes from the CKD programm)

The bottom line represents the distribution of the allowed transition intensities.

δν1/2=246 cm-1

0

50

100

150

200

250

300

350

30 40 50 60 70 80 90

Sum of mass of colliding molecules, amu

Ro

to-t

ran

slat

ion

al b

and

hal

f-w

idth

, cm

-1

Methane

Water vapor continuum, CKD

N2 broadened continuum,

Pure nitrogen CO2

Page 23: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

Is the continuum a cumulative contribution of line far wings?

Yes: Theoretical justification.

No: It is hard to understand continuum’s not uniform temperature dependence. It is hard to explain why the continuum is shaped like typical CIA spectrum?

Page 24: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

Is the continuum absorption by water dimers?

Yes: Water dimers exist.

No: The main reason for the continuum “dimer” conception is its exponential temperature dependence with the exponent value close to the energy of dimer dissociation. But really it is not exponential and not uniform. There is no reasonable explanation for the nitrogen broadened continuum?It is hard to explain why the continuum is shaped like typical CIA spectrum?

Page 25: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

On a possible continuum origin

Is the continuum a water vapor Collision Induced Spectrum?

Yes: It is shaped like collision induced spectrum.

There is a very easy and clear explanation of the nitrogen broadened continuum.

Water vapor CIA spectrum exists and it is expected to be very strong because of the first order magnitude dipole-dipole induction.

No: A. Brown, R. H. Tipping, “Collision-induced absorption in dipolar molecule-homonuclear diatomic pairs”, C. Camy-Peyret and A. A. Vigasin (eds.), Weakly Interacting Molecular Pairs: Unconventional Absorbers of Radiation in the Atmosphere, 93-99 (2003) Kluwer Academic Publisher

Page 26: Yu. I. BARANOV, W. J. LAFFERTY, and G. T. Fraser Optical Technology Division Optical Technology Division National Institute of Standards and Technology,

Summary

Pure water vapor spectra have been recorded over a wide range of temperatures and pressures. Continuum binary absorption coefficients have been determined in the regions 800 to 1300 and 1930 to 2300 cm-1.  In the 800 to 1300 cm-1 region our data for lower temperature reasonably agree with data provided with CKD model. But the disagreement increases up to 50% at high temperatures. In the high frequency segment our data satisfactory agree with CKD values around 2000 cm-1. But at higher wavenumbers the measured values greatly exceed the model. The data presented show that over both regions the absorption coefficient temperature dependence is not purely exponential and not uniform.