1. LOW TEMPERATURE LINESHAPE OF HYDROGEN DEUTERIDE TF14 BRIAN J. DROUIN, HARSHAL GUPTA, JOHN C. PEARSON, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099. 6/23/20111Low Temperature Lineshape of HD

2. 6/23/2011Low Temperature Lineshape of HD2 90.7 GHz → 101.8 GHz New THz Source for Spectroscopy Power Spectrum Under purged conditions

3. 6/23/2011Low Temperature Lineshape of HD3 Previous work is tough to best 2.2 meters, 11.6 Torr Evenson, K. M., et al. 1988, Astroph. J., 330, L135

4. 6/23/20114Low Temperature Lineshape of HD Cyro-cooled cell may help Cell designed for collisional cooling, pathlength is 15 cm, windows are mylar Temperature range is 18 – 200 K

5. 6/23/2011Low Temperature Lineshape of HD5 More than a narrower line Cooling of the 10 Torr HD sample produced multiple effects: (1)The gas pressure decreased (of course) (2)The intensity increased (3)The Doppler width became narrower than the Lorentz width (4)The line-center shifted 0.15-1.96 Torr HD 19 K 15 cm path

6. HD self shift gives line center to 10 kHz Evenson et al. 1988; 2674986.66(15) This work; 2674986.124(10) Evenson et al. Ap.J. 1988 6/23/20116Low Temperature Lineshape of HD Significant Improvement

7. 6/23/20117Low Temperature Lineshape of HD Experiment: Evenson Ap. J. 1988 2674986.66(15) MHz Theory: Pachuki & Komasa 2010 2674986.136(240) MHz Phys. Chem. Chem. Phys., 12, 9188. Careful linecenter determination required Drouin et al. 2011 (J. Mol. Struct. in press) 2674986.094(25) MHz

8. 6/23/2011Low Temperature Lineshape of HD8 More than a narrower line – a sub-Doppler line! Doppler halfwidth at 18 K is 2.2 MHz Voigt function? Only works above the minimum > 1 Torr for HD-HD broadening, lower for foreign gases

9. 6/23/20119Low Temperature Lineshape of HD 10 MHz Temperature18K, Pressures 0.05-10 Torr HD 0.5 Torr HD, 0-10 Torr pH2 or He Foreign Broadening Gases, p-H 2 and He Pearson et al. Rev. Sci. Instr. in press 2011.

10. 6/23/2011Low Temperature Lineshape of HD10 Figures 9a* (pressure broadening cross section) and 9b* (pressure shift cross section) (left) ● pH2 ● nH2 broadening, ♦ ♦ He broadening (right) ● pH2 ● nH2 shift, ■ He shift A.Schaefer J, Monchick L, “Line Broadening Of HD Immersed In He And H-2 Gas.” Astron. & Astrophys. 265, 859-868, 1992.Line Broadening Of HD Immersed In He And H-2 Gas B. Ulivi L, Lu Z, Tabisz GC, “Temperature-Dependence of The Collisional Interference In The Pure Rotational Far-Infrared Spectrum Of HD.” Phys. Rev. A, 40(2) 642-651, 1989. Foreign Broadening Gases, Theory vs. Exp.

11. 6/23/2011Low Temperature Lineshape of HD11 Conclusions and Future Work Conclusions The linecenter of HD was better determined through ab initio calculation (until now) Planetary and Astrophysical Models can utilize calculated Broadening and Shifts if accuracy of 20-50% is OK Line narrowing parameters will be important in foreign gases Future Work  The three temperature points are not enough to validate a non-linear trend we have proposed extensive temperature measurements  Motional narrowing can be accommodated with sophisticated models e.g. K-S “correlated” functionals

12. 6/23/2011Low Temperature Lineshape of HD12 Acknowledgements We would like to thank Ed Cohen for guidance. NASA’s Astronomy and Physics Research and Analysis program (APRA) for funding Herschel Science Center Also: Copyright 2011 California Institute of Technology. Government sponsorship acknowledged