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Line-shapes and intensities of carbon monoxide transitions in the (3 Line-shapes and intensities of carbon monoxide transitions in the (3

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Line-shapes and intensities of carbon monoxide transitions in the (3 - PPT Presentation

0 band   Z Reed O Polyansky J Hodges National Institute of Standards and Technology University College of London Carbon monoxide Line Shapes and Intensities ID: 630674

measured line fit speed line measured speed fit dependent nist pressure transition frequency profile broadened 00e narrowing shifting broadening

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Slide1

Line-shapes and intensities of carbon monoxide transitions in the (3 0) band

 

Z. Reed,* O. Polyansky,† J. Hodges** National Institute of Standards and Technology† University College of LondonSlide2

Carbon monoxide Line Shapes and IntensitiesCarbon monoxide is present in the planetary atmospheres of most planets in this solar system and is a useful probe of atmospheric dynamics CO is an excellent test case for lineshape modelingCO can readily be modeled

theoretically, presenting a possible approach to link optical measurements to the SI without the use of artifact gas standardsSlide3

Previous WorkExtensive study has been performed on self-, nitrogen-, and air-broadened CO in the

,

, and bands [1]

Intensities of the

band have been previously determined [1-3]

Systematic variation from the Voight profile has been revealed, along with deviations from HITRAN2012 line intensities and a dependence on chosen line shape model

 

[1]

Mondelain

, D., et al., Broadband and highly sensitive comb-assisted cavity ring down spectroscopy of CO near 1.57

μm

with sub-MHz frequency accuracy. Journal of Quantitative Spectroscopy and Radiative Transfer, 2015. 154: p. 35-43

[2]

Wójtewicz

, S., et al., Low pressure line-shape study of self-broadened CO transitions in the (3←0) band. Journal of Quantitative Spectroscopy and Radiative Transfer, 2013. 130: p. 191-200. [3] Henningsen, J., et al., The 0 → 3 Overtone Band of CO: Precise Linestrengths and Broadening Parameters. Journal of Molecular Spectroscopy, 1999. 193(2): p. 354-362. Slide4

frequency

-

stabilized

reference laser

cw

probe laser

cavity stabilization servo

pzt

optical resonator

decay signal

(a)

(b)

time

stabilized comb of

resonant frequencies

n

FSR

= 108 MHz

absorption spectrum

frequency

4

Frequency Stabilized Cavity Ringdown Spectroscopy (FS-CRDS) at NIST Gaithersburg

Hodges, J.T., et al, Rev. Sci.

Instrum

., 2005, 76, 2

1/(c

t)

=

a

0

+

a

(

n

)

time

frequency

I = I

0

exp

-(t/

t

) +

constSlide5

Linking measured line parameters to the SIGas-filled, length-stabilized

ring-down cavity

I2-stabilizedHeNe laser (10 kHz)Probe LaserOptical FrequencyComb

CsClockProbe laser servo

Primary Pressure

Standards

Primary Temperature

Standards

Calibrated

Thermometers (PRT)

Calibrated

Manometers (SRT)

Cavity length

servo

1/(c

t)

=

a

0

+

a

(

n

)

time

frequencySlide6

Measurement of Line Intensity (S) and Absorber Concentration (n)

S

=

a(n

)

d

n

/{

n

g(n)d

n} =

A

/

n

line profile

(unity area)

fitted spectrum area

measured

absorption coefficient

Once the intrinsic property

S

is known, then

n

=

A

/SSlide7

Hartmann-Tran Line ProfileIncludes mechanisms for collisional narrowing, speed dependent narrowing and shifting, and correlation between velocity- and phase- changing collisions

Average broadening

Speed dependent broadening

Average shifting

Speed dependent shifting

Collisional

narrowing

Correlation

η

Average broadening

Speed dependent broadening

Average shifting

Speed dependent shifting

Collisional

narrowing

Correlation

ηSlide8

HTP Profile reduces to:Voight profile (VP) when

,

, , η = 0Nelkin-Ghatak (NGP) when

,

,

η

= 0

Speed-dependent VP when

,

η

= 0

Quadratic speed dependent NGP when

,

η

= 0Where

=

absorber mass

mass

diffusion coefficient

 

Quadratic approximation

to speed dependence

Complex, normalized

narrowing frequency

Complex profile

Mechanisms: 1) collisional narrowing (hard-collision model), 2) speed-dependent broadening and shifting,

3) partial correlations between velocity-changing and

dephasing

collisionsSlide9

Line Profiles

Measured and fit results of the N

2-broadened 13CO transition P3, measured at a total pressure of 13.33 kPa and 296KUpper panel, measured (symbols) and fit (line) absorption spectrumLower panes show fit residuals and QF values for individual profilesSlide10

Line Profiles

Measured and fit results of the N

2-broadened 13CO transition P3, measured at a total pressure of 13.33 kPa and 296KUpper panel, measured (symbols) and fit (line) absorption spectrumLower panes show fit residuals and QF values for individual profiles

α

(

ν

)=A{Re I (

ν

-

ν

0

) + Y

Im

(I (ν- ν0)) }Where A = fitted area

Y= dimensionless line mixing term Re(I) = real component Im (I)= imaginary componentLine MixingSlide11

Fitted Area Dependence

Relative fitted area of N

2-broadened 13CO transition P3 measured at a total pressure of 13.33 kPa and 296K, as a function of varying line profiles.Voight profile systematically underestimates line areaSlide12

Line Intensity Determination

Once the intrinsic property

S is known, then n = A/S

n

must be known to determine S

NIST

CO in N

2

standard prepared via gravimetric weighing method

11.9858%

±

0.00095 CO in N

2

Slide13

Line Intensity Determination

Linear fit of fitted line areas of N

2-broadened

13CO transition P3 measured at 296K at pressures ranging from 50 torr to 350 torr. Spectra are fitted with SDNGP profile with line mixing.

GP

SDNGP

SDNGP+LM

S (cm

-1

/(

molec

. cm

-2

)1.0146E-25

1.0151E-251.0153E-25

Uncertainty (%)

0.031

0.010

0.0083Slide14

Measurement repeatability

Transition

Transition no.

S (NIST

)

(cm

-1

/(

molec

. cm

-2

)

uncertainty (%)

12C16O   P26

1

1.161E-25

0.043

12

C

16

O

  

P27

2

7.239E-26

0.054

12

C

16

O

  

P28

3

4.416E-26

0.12

13

C

16O   P1

43.77E-26

0.14

13C16O   P2

5

7.20E-260.10

13C16

O   P36

1.013E-25

0.29

13C16O   R0

7

3.972E-260.23

12C18O R4

8

3.26E-260.19

 

  

 

Normalized line strengths determined via repeated experiment (symbols). Error bar represent individual fit uncertainty

Calculated line strengths and combined uncertaintySlide15

Comparison to Literature and TheoryAll electron MRCI calculations with highest available basis set in MOLPROAug-cc-pCV6Z results are extrapolated to complete basis set limitFirst and second order relativistic corrections and adiabatic corrections included

[1] Wójtewicz, S., et al., Low pressure line-shape study of self-broadened CO transitions in the (3←0) band. JQSRT, 2013. 130: p. 191-200.

[2] A. A. Kyuberis, L. Lodi, V. Ebert, N. F. Zobov, J. Tennyson, O. L. Polyansky

Isotope

Transition

Wojtewicz

1

% diff w.r.t NIST

HITRAN

% diff w.r.t NIST

Ab initio

% diff w.r.t NIST

12

C

16

O

P26

-

0.34

-

0.13

P27

-2.51

-

0.67

-

0.06

P28

-3.06

-

0.58

0.05

13

C

16

O

P1

-1.25

10.61

P2

-1.71

10.44

P3

-0.49

10.89

R0

9.44

12

C

18

O

R4

3.28Slide16

Error Budget

Isotope

Transition

Intensity

Uncertainty

(cm

-1

/

(

molec

. cm

-2

)

%

12

C

16

O

P26

1.16E-25

0.043

P27

7.24E-26

0.054

P28

4.42E-26

0.12

13

C

16

O

P1

3.77E-26

0.14

P2

7.20E-26

0.1

P3

1.01E-25

0.29

R0

3.97E-26

0.23

12

C

18

O

R4

3.26E-26

0.19

NIST uncertainties (not including fit)

unc. (%)

unc

2

pressure

5.00E-03

2.50E-05

composition

7.93E-03

6.28E-05

isotopic composition

1.00E-02

1.00E-04

Temperature

5.00E-02

2.50E-03

Pressure zero drift

2.00E-03

4.00E-06

combined (%)

0.05188Slide17

ConclusionsLine strengths of selected 12C16O, 13

C16O, and 12C18O transitions in the (3

0) band measured at highest precision to dateCalculated line strengths vary significantly from HITRAN and previous literature values, but compare well to ab initio calculationsLink to SI and theoretical line strengths demonstrates possible route to artifact-free determination of molecular concentrations, including isotope ratios 

Funding: NIST Greenhouse Gas Measurements and Climate Research Program