1. Sub-Doppler Spectroscopy of H 3 + James N. Hodges, Adam J. Perry, Brian M. Siller, Benjamin J. McCall

2. Outline Motivation –Fundamental Physics –Astronomy Instrument Description Transition Frequency Results Wavelength Calibration Testing

3. H 3 + Fundamental Benchmark Simplest polyatomic ion Benchmark for ab initio theory –Accuracy of order 300 MHz @ low energy QED corrections are frontier –Accuracy of order 30 MHz @ low energy Requires higher precision data O. L. Polyansky, J. Tennyson, J. Chem. Phys. (1999), 110, 5056-5064. J. Komasa, et al. J. Chem. Theor. Comp. (2011), 7, 3105-3115.

4. H 3 + Astronomically Important Abundant in Interstellar Medium Deuterium Fractionation Found in Ionospheres of Gas Giants Measure Speed of Auroral Winds Limited by Laboratory Accuracy T. R. Geballe and T. Oka, Nature (1996), 384, 334. P. Drossart et al. Nature (1989), 340, 539. D. Rego et al. Nature (1999), 399, 121. Images From: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter http://www.ucl.ac.uk/~ucaptss/work/publications/royalsoc/energy.htm

5. Spectroscopic Technique Large Signal Low Noise Ion Selectivity Cavity Enhancement Heterodyne Spectroscopy Velocity Modulation NICE- OHVMS Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy B. M. Siller, et al. Opt. Express (2011), 19, 24822-7.

6. Instrumental Layout OPO YDFL EOM Lock-In Amplifier X & Y Signal Lock-In Amplifier X & Y Signal Wave- meter 40 kHz Plasma Frequency 80 MHz 1 × Cavity Free Spectral Range 90 o Phase Shift IPSIPS 2f i  p  s Freq. Comb AOM K. N. Crabtree, et al. Chem. Phys. Lett. (2012), 551, 1-6.

7. Comb Calibration Wave- meter Freq. Comb AOM […] SignalPump

8. Comb Calibration Wave- meter Freq. Comb AOM […] SignalPump

9. Comb Calibration Wave- meter Freq. Comb AOM […] SignalPumpSignal

10. H 3 + Spectra Signal Doubly Degenerate 2 Band H 3 + Transition Notation

11. Lamb Dips & Saturation High Power  Optical Saturation  Lamb dips Second Comb Calibrated Observation of Lamb dips In NICE-OHVMS fm-triplet causes many Lamb dips H.-C. Chen et al. Phys. Rev. Lett. (2012), 109, 263002. K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

12. Lamb Dips & Saturation High Power  Optical Saturation  Lamb dips Second Comb Calibrated Observation of Lamb dips In NICE-OHVMS fm-triplet causes many Lamb dips H.-C. Chen et al. Phys. Rev. Lett. (2012), 109, 263002. K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

13. Lamb Dips & Saturation High Power  Optical Saturation  Lamb dips Second Comb Calibrated Observation of Lamb dips In NICE-OHVMS fm-triplet causes many Lamb dips H.-C. Chen et al. Phys. Rev. Lett. (2012), 109, 263002. K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

14. Lamb Dips & Saturation High Power  Optical Saturation  Lamb dips Second Comb Calibrated Observation of Lamb dips In NICE-OHVMS fm-triplet causes many Lamb dips H.-C. Chen et al. Phys. Rev. Lett. (2012), 109, 263002. K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

15. Lamb Dips and Fits R(2,2) l Transition

16. Transition Frequencies St. Err. = St. Dev. Of Mean

17. Lamb Dip Signal-to-Noise-Ratio Lamb Dip SNR:

18. Lamb Dip Signal-to-Noise-Ratio R(1,0)R(3,2) l

19. Frequency Calibration Test First use of a comb with this instrument Need to ensure proper calibration Lamb dips of methane

20. Instrumental Layout OPO YDFL EOM Lock-In Amplifier X & Y Signal Lock-In Amplifier X & Y Signal Wave- meter 40 kHz Plasma Frequency 80 MHz 1 × Cavity Free Spectral Range 90 o Phase Shift IPSIPS 2f i  p  s Freq. Comb AOM 1.4 kHz Modulation Frequency 3f

21. Frequency Calibration Test First use of a comb with this instrument Need to ensure proper calibration Lamb dips of methane Acquired Lamb dips for F 1 (2) component of P(7) transition of 3 band

22. Frequency Calibration Test Lamb dip of methane Fit with 2 nd derivative of Lorentzian 5 kHz diff. from Takahata et al. ~30 kHz st. dev. from fit K. Takahata et al. Phys. Rev. A. (2009) 80, 032518.

23. Conclusions Comb calibrated H 3 + transitions reported Higher S/N lines have sub-MHz precision Methane used to validate comb calibration Values differ than Chen et al. H.-C. Chen et al. Phys. Rev. Lett. (2012), 109, 263002.

24. Acknowledgements Springborn Fellowship NSF GRF (DGE 11- 44245 FLLW)