1. High Precision Mid-Infrared Spectroscopy of 12 C 16 O 2 : Progress Report Speaker: Wei-Jo Ting Department of Physics National Tsing Hua University 2010.06.25 Department of Physics National Tsing Hua University 2010.06.25

2. Outline  Precision MIR source mW PPLN DFG source Frequency calibration  High resolution spectroscopy of CO 2 00 0 1← 00 0 0 @ 4.3 μm (Fundamental ν 3 band) [10 0 1,02 0 1] I ← 00 0 0 band @ 2.69 μm [10 0 1,02 0 1] II ← 00 0 0 band @ 2.76 μm 01 1 1← 01 1 0 @ 4.3 μm (Hot-band) [11 1 0,03 1 0] I ← 00 0 0 band @ 4.8 μm

3. mW PPLN DFG source Ti:Sapphire laser Nd:YAG laser MgO:PPLN Temperature stability < 0.05 ℃ Ge plate 1 W tunable: 700 ~1000 nm 8 W though fiber amplifier @1064nm DFG radiation 2 to 5  m ~7 mW @ 2.8  m 44 mm

4. Frequency calibration Ti:sapphire laser (f TiS ) Optical Frequency Comb Nd:YAG laser (f YAG ) Iodine hyperfine transition f TiS - f YAG =f DFG DFG absolute frequency

5. OFC performances Repetition frequency: 1 GHz Average power of supercontinuum: 420 mW Spectral range of supercontinuum: 500 ~ 1500 nm Stability of repetition frequency: 0.68 mHz Stability of offset frequency: 4 mHz Accuracy: 10 -12 @ 1 s (referenced to a GPS disciplined Rb clock)

6. Why CO 2 ? Most heterodyne frequency measurements are carried on CO 2 laser transitions A. G. Maki et al., J. Mol. Spectrosc. 167, 211 (1994) A. Amy-Klein, H. Vigué, C. Chardonnet, J. Mol. Spectrosc. 228, 206 (2004) Only one measurement for [10 0 1,02 0 1] I ← 00 0 0 band A. Groh et al., J. Mol. Spectrosc. 146, 161 (1991)

7. Energy diagram of CO 2 No good laser sources Frequency measurement is difficult before OFC is invented

8. Fundamental v 3 band: Fundamental v 3 band: Experimental set-up CaF 2 window InSb detector DFG CO 2 cell Lock-in amplifier Lock point

9. Fundamental v 3 band OSU ISMS 63th FA09

10. 56 P- and R-branch transitions up to J=60 (accuracy < 30 kHz) (see OSU 63th ISMS FA09) 10 high J (60<J<90) R-branch transitions (accuracy < 72 kHz) (see OSU 64th ISMS TG11) Molecular constants of the ground vibration level are greatly improved. Fundamental v 3 band

11. [10 0 1,02 0 1] I,II ← 00 0 0 Bands: Saturated 4.3 μm Fluorescence 2.7 μm laser pumping. Probing 4.3 μm fluorescent signal. Zero background, High S/N ratio.

12. Direct detection vs. Fluorescence detection Direct Detection Fluorescence Detection OSU ISMS 63th FA10

13. For [10 0 1,02 0 1] I ← 00 0 0, 19 transitions have been measured to an accuracy of 40 kHz Accurate molecular constants of the [10 0 1,02 0 1] I vibrational level have been determined (see OSU 63rd ISMS FA10) [10 0 1,02 0 1] I ← 00 0 0 Band

14. For [10 0 1,02 0 1] II ← 00 0 0 weaker band Old design New design 8.7 times enhancement New design for fluorescence signal enhancement Reduce the distance between L-cell and detector. Use larger area InSb detector (diameter from 4 mm to 7 mm) One order of magnitude improvement!

15. [10 0 1,02 0 1] II ← 00 0 0 Band P(20) fluorescence signal Need more effort to enhance the signal… New focusing lens for saturation intensity. Boost DFG Power Better light overlapping.

16. Hot Band: Signal enhancement Quartz glass tube Total Cell length: 60 cm Nickel-Chromium wire heater wind over the cell Quartz glass tube Total Cell length: 60 cm Nickel-Chromium wire heater wind over the cell

17. Hot band signal Third-derivative saturated absorption spectrum of 01 1 1←01 1 0 P(30) transition. The gas pressure was 30 mTorr at 700 K.

18. Weak transitions near 01 1 1-01 1 0 P(30) L1: 12 C 16 O 2 20 0 1-20 0 0 R(4) L2: 16 O 12 C 18 O 01 1 1-01 1 0 P(12)f L3: CO 2 01 1 1-01 1 0 P(30) L4: 16 O 12 C 18 O 01 1 1-01 1 0 P(12)e L5: 12 C 16 O 2 03 3 1-03 3 0 Q(19)

19. Measurement results TransitionThis work a (MHz)HITRAN b (MHz) Difference a － b (MHz) 12 C 16 O 2 01 1 1-01 1 0 P(30) 69 267 228.761 (20)69 267 225.23-3.531 12 C 16 O 2 20 0 1-20 0 0 R(4) 69266995.409 (95)69266944.86250.547 16 O 12 C 18 O 01 1 1-01 1 0 P(12)f 69267025.884 (139)69266986.05339.831 16 O 12 C 18 O 01 1 1-01 1 0 P(12)e 69267481.268 (151)69267441.64839.620 12 C 16 O 2 03 3 1-03 3 0 Q(19) 69267536.410 (115)69267857.700- 321.290

20. Future works High J transitions of fundamental band New measurements on [10 0 1,02 0 1] II ← 00 0 0 band More measurements on 01 1 1 ← 01 1 0 band (hot band) [11 1 0,03 1 0] I ←00 0 0 band

21. [11 1 0, 03 1 0] I ← 00 0 0 band @ 4.8 μm [11 1 0, 03 1 0] I ← 00 0 0 band @ 4.8 μm 01 1 1 00 0 0 [11 1 0,03 1 0] I 01 1 0 CO 2 laser 10.8 μm Hot-band 16 μm [11 1 0, 03 1 0 ] I ← 00 0 0 band 1000 times weaker. 2075 cm -1 (4.8 μ m) Cavity enhancement [11 1 0, 03 1 0 ] I ← 00 0 0 band 1000 times weaker. 2075 cm -1 (4.8 μ m) Cavity enhancement

22. Thank Dr. Maki for valuable suggestions. He will also do the globe fitting after we finish all measurements Thanks for your attention!