High Precision Mid-IR Spectroscopy of 12C16O2Near 4.3 μm Speaker: Wei-Jo TingDepartment of Physics, National Tsing Hua University, Hsinchu, TaiwanJune 23, 2009

Motivation• Continue our previous study : absolute frequencies of fundamental band transitions with J up to 60 (accuracy < 30 kHz).• Fewer high J frequency data in HITRAN database..

Experimental Set-up (1)Ti:Sapphire

Nd:YAG laser MgO2 :PPLN

Temperature stability < 0.005 ℃

Ge plate

1 W tunable: 760 ~870 nm

1 W 1064nm

DFG radiation 55 μW50 mm

Experimental Set-up (2)

Temperature~ 500 ℃Pressure @ 31mm torr

CaF2 window

InSb detector

DFG

Hot CO2 cell

Lock-in amplifier

Lock point

Frequency Calibration• Ti:Sapphire laser (fTiS)Locked onto the CO2 3rd derivative signalOptical Frequency Comb Accuracy~ 30 kHz• Nd:YAG laser (fYAG)Offset locked to iodine-stabilized Nd:YAG laser127I2 R(56)32-0 a10 hyperfine transitionfTiS- fYAG=fDFG absolute frequency

Frequency Calibration• Ti:Sapphire laser (fTiS)Locked onto the CO2 3rd derivative signalOptical Frequency Comb Accuracy~ 30 kHz• Nd:YAG laser (fYAG)Offset locked to iodine-stabilized Nd:YAG laser127I2 R(56)32-0 a10 hyperfine transitionfTiS- fYAG=fDFG absolute frequency

Frequency Calibration• Ti:Sapphire laser (fTiS)Locked onto the CO2 3rd derivative signalOptical Frequency Comb Accuracy~ 30 kHz• Nd:YAG laser (fYAG)Offset locked to an iodine-stabilized Nd:YAG laser127I2 R(56)32-0 a10 hyperfine transitionfTiS- fYAG=fDFG absolute frequency

Frequency Calibration• Ti:Sapphire laser (fTiS)Locked onto the CO2 3rd derivative signalOptical Frequency Comb Accuracy~ 30 kHz• Nd:YAG laser (fYAG)Offset locked to an iodine-stabilized Nd:YAG laser127I2 R(56)32-0 a10 hyperfine transitionfTiS- fYAG=fDFG absolute frequency

Signal Enhancement (1)• R(60) 10 times enhanced from 27 ℃ to 600 ℃• R(100) 30000 times enhanced from 27 ℃ to 600 ℃

Line strength versus temperature , R(60) and R(100)

0 100 200 300 400 500 600 700

3.33E-26

3.33E-25

3.33E-24

3.33E-23

3.33E-22

3.33E-21

3.33E-20

R(60)

R(100)

Temperature ( )℃

Line

Str

engt

h (c

m-1

/(m

olec

ule

× cm

-2))

Signal Enhancement (1)• R(60) 10 times enhanced from 27 ℃ to 600 ℃• R(100) 30000 times enhanced from 27 ℃ to 600 ℃

• Quartz glass tube • Total Cell length: 60 cm • Nickel-Chromium wire heater wind over the cell

Line strength versus temperature , R(60) and R(100)

0 100 200 300 400 500 600 700

3.33E-26

3.33E-25

3.33E-24

3.33E-23

3.33E-22

3.33E-21

3.33E-20

R(60)

R(100)

Temperature ( )℃

Line

Str

engt

h (c

m-1

/(m

olec

ule

× cm

-2))

Signal Enhancement (2)

0 100 200 300 400 500 6000.00E+00

1.00E-04

2.00E-04

3.00E-04

4.00E-04

5.00E-04

6.00E-04

7.00E-04

measured R(66) measured R(60)R(60) prediction R(66) prediction

tube Temperature )℃

Sign

al S

tren

gth

(a.u

.)

1st derivative signal Doppler width

S: line strength T: temperature1 st derivative signal strength of the Doppler broadened profile versus temperature

Prediction

Experimental results agree with predictions.

Typical SpectrumR(70)Pressure @ 31 m torrTemperature @ 487 °C S/N ratio : 110

65 70 75 80 85 90 95 100 105 110 115-8.00E-05

-6.00E-05

-4.00E-05

-2.00E-05

0.00E+00

2.00E-05

4.00E-05

6.00E-05

The third-derivative Lamb-dip spectrum of R(70) transition

Inte

nsity

(a.u

)

Frequency ( a.u.)

Uncertainty

Uncertainty• OFC 5 kHz

Uncertainty• OFC 5 kHz• Iodine stabilized Nd:YAG laser 4 kHz

Uncertainty• OFC 5 kHz• Iodine stabilized Nd:YAG laser 4 kHz• Nd:YAG laser offset locking 30 kHz

Uncertainty• OFC 5 kHz• Iodine stabilized Nd:YAG laser 4 kHz• Nd:YAG laser offset locking 30 kHz• Ti:sapphire laser locking 33 kHz

Uncertainty• OFC 5 kHz• Iodine stabilized Nd:YAG laser 4 kHz• Nd:YAG laser offset locking 30 kHz• Ti:sapphire laser locking 33 kHz The worst case, uncertainty = 72 kHz

Observed Transitions Transition

Measured Frequency

(kHz)

Prediction from our previous laboratory data

Prediction from HITRAN04

Frequency (kHz) Difference (kHz)

Frequency (kHz) Difference (kHz)

R64 71 546 328 918 (48) 71 546 328 873 81 71 546 328 917 1

R66 71 568 188 557 (31) 71 568 188 422 135 71 568 187 984 572

R68 71 589 286 873 (31) 71 589 286 603 271 71 589 285 429 1 444

R70 71 609 623 152 (33) 71 609 622 758 394 71 609 620 591 2 561

R72 71 629 196 831 (30) 71 629 196 269 562 71 629 192 842 3 989

R78 71 683 336 284 (34) 71 683 334 808 1 476 71 683 325 406 10 877

R82 71 715 605 364 (35) 71 715 602 766 2 598 71 715 587 092 18 271

R84 71 730 590 975 (36) 71 730 587 615 3 360 71 730 567 961 23 014

R86 71 744 809 909 (39) 71 744 805 580 4 329 71 744 781 301 28 608

R88 71 758 261 568 (32) 71 758 256 065 5 503 71 758 226 454 35 114

R90 71 770 945 409 (72) 71 770 938 472 6 937 71 770 902 758 42 651

Molecular Constants Fitting

4.3 μm

9.4 μm10.4 μm

0000

0001

[1000, 0200] I,II

Molecular Constants Fitting

4.3 μm

9.4 μm10.4 μm

0000

0001

[1000, 0200] I,II

Precise molecularconstants of 0001 state By Amy-Klein et al.

Molecular Constants Fitting

4.3 μm

9.4 μm10.4 μm

0000

0001

[1000, 0200] I,II

Precise molecularconstants of 0001 state By Amy-Klein et al.

This work: Refine 0000 state

Molecular Constants Fitting

4.3 μm

9.4 μm10.4 μm

0000

0001

[1000, 0200] I,II

Precise molecularconstants of 0001 state By Amy-Klein et al.

This work: Refine 0000 state

Fitting formula: F(J) is rotational energy Fv(J) = BvJ(J +1)−DvJ2(J +1)2+HvJ3(J +1)3+LvJ4(J

+1)4+· · ·

Molecular Constants (1)Constants This Work Amy et.al. b

0001←0000

ν0 2349.142 788 683 (92)

B(0001) 0.387 141 391 966

D(0001) ×107 1.330 275 6

H(0001) ×1013 0.152 7

L(0001) ×1019 2.30

B(0000) 0.390 218 955 5 (3)

D(0000) ×107 1.333 799 4 (22)

H(0000) ×1013 0.141 87 (55)

L(0000) ×1019 -2.450 (42)

a. All values in cm −1. 1 σ uncertainty given in the last digit is given in parentheses.b. A. Amy-Klein, H. Vigue, C. Chardonnet, J. Mol. Spectros. 228, 206-212 (2004).

Molecular Constants (2)Constants This Work Previous work in lab b Miller et al. c

ν0 2349.142 788 683 (92) 2349.142 787 992 (303) 2349.142 683 4 (117)

B(0000) 0.390 218 955 5 (3) 0.390 218 954 8 (11) 0.390 218 949 (36)

D(0000) ×107 1.333 799 4 (22) 1.333 785 9 (92) 1.334 088 (186)

H(0000) ×1013 0.141 87 (55) 0.134 79 (275) 0.191 8 (250)

L(0000) ×1019 -2.450 (42) -1.135 (257) ─

The accuracy of molecular constants have been improved 3 times. a. All values in cm −1. 1 σ uncertainty given in the last digit is given in parentheses.b. Previous study from our laboratory in fundamental band transitions with J < 60c. C. E. Miller et al., J. Mol. Spectrosc. 228, 329-354 (2004).

Summary • Heating CO2 to ~ 500 ℃ to enhance the line strength of J > 60 transitions .

• The absolute frequencies of 10 R-branch transitions (J = 66, 68, 70, 72, 78, 82, 84, 86, 88, 90) with uncertainty < 72 kHz.• Combining with our previous measurements to refine the molecular constants of the ground vibrational level and the vibrational energy of 0001 level.

Summary • Heating CO2 to ~ 500 ℃ to enhance the line strength of J > 60 transitions .

• The absolute frequencies of 10 R-branch transitions (J = 66, 68, 70, 72, 78, 82, 84, 86, 88, 90) with uncertainty < 72 kHz.• Combining with our previous measurements to refine the molecular constants of the ground vibrational level and the vibrational energy of 0001 level.

Summary • Heating CO2 to ~ 500 ℃ to enhance the line strength of J > 60 transitions .

• The absolute frequencies of 10 R-branch transitions (J = 66, 68, 70, 72, 78, 82, 84, 86, 88, 90) with uncertainty < 72 kHz.• Combining with our previous measurements to refine the molecular constants of the ground vibrational level and the vibrational energy of 0001 level.

Summary • Heating CO2 to ~ 500 ℃ to enhance the line strength of J > 60 transitions .

• The absolute frequencies of 10 R-branch transitions (J = 66, 68, 70, 72, 78, 82, 84, 86, 88, 90) with uncertainty < 72 kHz.• Combining with our previous measurements to refine the molecular constants of the ground vibrational level and the vibrational energy of 0001 level.

Future Works 0111← 0110 band• Hot band transitions 30 times weaker.• Increase DFG power.• Heating CO2 gas, increase population.• Molecular const. fitting.

AcknowledgementDFG group:Chieh-Hsing Chung, Pei-Ling LuoOFC group:Hshan-Chen Chen, Dr. Yu-Hung Lien Professor Jow-Tsong Shy$$ NSC & MOE of Taiwan

Thank you!