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

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:

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,

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.

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

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

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

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

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, K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

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, K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

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, K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

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, K.N. Crabtree et al. Chem. Phys. Lett. (2012), 551, 1.

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

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

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

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

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

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

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

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,

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,

Acknowledgements Springborn Fellowship NSF GRF (DGE FLLW)