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Sub-Doppler Spectroscopy of H 3 +

Sub-Doppler Spectroscopy of H 3 +. James N. Hodges , Adam J. Perry, Brian M. Siller , Benjamin J. McCall. Outline. Motivation Fundamental Physics Astronomy Instrument Description Transition Frequency Results Wavelength Calibration Testing. H 3 + Fundamental Benchmark.

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Sub-Doppler Spectroscopy of H 3 +

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  1. Sub-Doppler Spectroscopy of H3+ 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. H3+ 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. H3+ 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 Cavity Enhancement NICE-OHVMS Low Noise Heterodyne Spectroscopy Ion Selectivity Velocity Modulation Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy B. M. Siller, et al. Opt. Express (2011), 19, 24822-7.

  6. Instrumental Layout ni = np - ns I P S OPO Freq. Comb AOM 90o Phase Shift Wave-meter 40 kHz Plasma Frequency 2f Lock-In Amplifier EOM Lock-In Amplifier 80 MHz 1 × Cavity Free Spectral Range YDFL X & Y Signal X & Y Signal K. N. Crabtree, et al. Chem. Phys. Lett. (2012), 551, 1-6.

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

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

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

  10. H3+ Spectra Doubly Degenerate 2 Band Signal Signal H3+ 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(3,2)l R(1,0)

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

  20. Instrumental Layout ni = np - ns I P S OPO Freq. Comb AOM 90o Phase Shift Wave-meter 1.4 kHz Modulation Frequency 40 kHz Plasma Frequency 2f 3f Lock-In Amplifier EOM Lock-In Amplifier 80 MHz 1 × Cavity Free Spectral Range YDFL X & Y Signal X & Y Signal

  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 F1(2) component of P(7) transition of 3 band

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

  23. Conclusions Comb calibrated H3+ 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)

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