1. OBSERVATION AND ANALYSIS OF THE A 1 -A 2 SPLITTING OF CH 3 D M. ABE*, H. Sera and H. SASADA Department of Physics, Faculty of Science and Technology, Keio University, Yokohama, Japan. *Current address: NTT Device Technology Laboratories TF03 70 th. International Symposium on Molecular Spectroscopy June 23, 2015, The University of Illinois at Urbana-Champaign

2. Outline Introduction  A wide-beam enhanced-cavity absorption cell (ECAC)  An optical frequency comb (OFC) with controlled carrier- envelope-offset frequency Spectroscopy of 12 CH 3 D and absolute frequency determination of the A 1 -A 2 components Analysis of the A 1 -A 2 splittings Summary

3. Introduction pump signal idler waveguide PPLN enhanced-cavity absorption cell (ECAC) Our spectrometer 600 kHz 160 kHz The wide beam reduces the transit-time broadening. Using previous ECAC (TF01, 02)Using a wide-beam ECAC the Q(12) transition of 12 CH 4 in the 3 band

4. Wide-beam ECAC 38 cm 3.8 mm 7 m effective absorption lengthoptical field strength at antinodes ×500(190 m)×15 mirror separation (FSR) finesse (FWHM)reflectivity (transmittance) 38 cm (400 MHz)770 (0.5 MHz)99.6% (0.3%) 30 cm A cavity coupled with a wide beam Cavity configuration 69 th ISMS TJ-13

5. Introduction pump signal idler waveguide PPLN enhanced-cavity absorption cell (ECAC) Our spectrometer ・・・ 0 idler  YAG  ECLD An optical frequency comb with controlled f CEO f CEO signal 400 kHz f rep ~97 MHz f CEO, f rep,  YAG,  ECLD : controled with RF synthesizers based on Rb clock linked TAI (relative uncertainty 10 -12 at 1 s) f CEO = 30 MHz

6. Spectrometer PPLN EOM pump (1.06  m) signal (1.5  m) FA idler (3.4  m) Er-OFC f rep = 97 MHz Extended Cavity Laser Diode （ ECLD ） Nd:YAG Laser InSb detector acquiring the spectra RF synthesizer PI controller ECAC InSb detector sweep f rep PZT CH 3 D the ECAC and the OFC are different from those in Kana’s talk (TF02)

7. CH 3 D A 1 -A 2 splitting K =2 K =3 K =4 J=5 J=3 J=4 J=2 J=5 J=3 J=4 J=2 Vibrational excited state Vibrational ground state E K  l =3 K  l =2 K  l =4 Q(J=3,K=3) A1A1 A2A2 E Energy separation between A 1 and A 2 levels in J

8. Spectrometer resolution 120 kHz Sub-Doppler resolution spectrum of 12 CH 3 D 1 band q Q(3,3) transition Averaging time: 16 Spectral linewidth (HWHM): 80 kHz pressure broadening: 2 kHz (pressure: 0.1 Pa) transit time broadening: 38 kHz source width: 20 kHz =>power broadening <60 kHz

9. Absolute frequency measurement 12 CH 3 D 4 band r Q branch spectra 30 transitions including 23 pairs of A 1 -A 2 splittings TransitionAssignmentObs. Freq. / kHz Obs. – HITRAN / MHz r Q(7, 3)A1A1 90 603 739 403.0(38)15.40 A2A2 90 603 739 634.9(33)15.63 r Q(8, 3)A2A2 90 595 966 750.8(36)16.36 A1A1 90 595 967 245.9(27)16.86 r Q(9, 3)A1A1 90 587 505 479.5(27)18.47 A2A2 90 587 506 416.0(31)19.47 ………… Relative uncertainty: 10 -11

10. Vibrational ground state r Q(8,3) r R(7,3)                9 pairs of  1 +  2 →determining the splitting coefficient r Q(J,3) r R(J-1,3) 2h 3 =(1.5641±0.0026) Hz least square fit (J,K=4) (J,K=3) (J-1,K=3)      obs.      calc. | ~ 

11. Vibrational excited state K =3 J=5 J=3 J=4 J=3 J=4 v 1 = 1 K =3 ( l =0) J=2 J=3 J=7 J=4 v 4 = 1 K =2 ( l =-1) v 4 = 1 K =4 ( l =+1) J=6 from the preceding calculations determined vibrational state splitting E

12. Vibrational excited state K =3 J=5 J=3 J=4 J=3 J=4 v 1 = 1 K =3 ( l =0) J=2 J=3 J=7 J=4 v 4 = 1 K =2 ( l =-1) v 4 = 1 K =4 ( l =+1) J=6 from calculation (front page) determined vibrational state splitting E 2h 3 (0) = (154±3) Hz 2h 3 (1) = (2.02±0.14) Hz 2h 3 (2) = (–24.7±1.5) mHz

13. Vibrational excited state K =3 J=5 J=3 J=4 J=3 J=4 v 1 = 1 K =3 ( l =0) J=2 J=3 J=7 J=4 v 4 = 1 K =2 ( l =-1) v 4 = 1 K =4 ( l =+1) J=6 from calculation (front page) determined vibrational state splitting E 2h 2 (0) = (99.32±0.09) kHz 2h 2 (1) = (509±6) Hz 2h 2 (2) = (4.22±0.08) Hz

14. Vibrational excited state K =3 J=5 J=3 J=4 J=3 J=4 E v 1 = 1 K =3 ( l =0) J=2 J=3 J=7 J=4 v 4 = 1 K =2 ( l =-1) v 4 = 1 K =4 ( l =+1) J=6 determined vibrational state splitting 2h 4 (0) = (–3.0±0.3) mHz 2h 4 (1) = (54.5±2.4) mHz Higher order rotation-vibration interactions affect splitting constants in the vibrational excited state. from the preceding calculations

15. Summary –We have introduced an enhanced-cavity absorption cell coupled with a wide beam to reduce the transit-time broadening. In addition, we introduced a new optical frequency comb whose carrier envelope offset frequency is controlled. The linewidth of the Lamb dips thereby reduced less than 100 kHz. –We have determined the absolute frequencies of 23 A 1 -A 2 pairs of 12 CH 3 D with a relative uncertainty of 10 –11. –We have determined the A 1 -A 2 splitting constants of the vibrational ground and excited states.

16. Summary –We have introduced an enhanced-cavity absorption cell coupled with a wide beam to reduce the transit-time broadening. In addition, we introduced a new optical frequency comb whose carrier envelope offset frequency is controlled. The linewidth of the Lamb dips thereby reduced less than 100 kHz. –We have determined the absolute frequencies of 23 A 1 -A 2 pairs of 12 CH 3 D with a relative uncertainty of 10 –11. –We have determined the A 1 -A 2 splitting constants of the vibrational ground and excited states. Thank you for your attention.

17. Appendix

18. Super combination difference From the result of JMS 312 p. 90

19. Transition list From the result of JMS 312 p. 90

20. Transition list From the result of JMS 312 p. 90

21. Transition list From the result of JMS 312 p. 90

22. Transition list From the result of JMS 312 p. 90

23. Transition list From the result of JMS 312 p. 90