1. DETERMINATION OF PRESSURE BROADENING AND SHIFTS FOR THE FIRST OVERTONE 2←0 OF HCL Brennan M. Coffey, Brian J. Drouin, Timothy J. Crawford Jet Propulsion Laboratory, California Institute of Technology 6/16/2014MK10 HCl Overtone Lineshapes1

2. Motivation Textbook case – but precision is not up to modern standards – Last Investigation into the line centers of HCl in the MIR was done by Guelachvili Opt. Comm. 19(1) 150-154, 1976 line positions to ~2x10 -4 cm -1 Laboratory calibration – Wavenumber calibration for 6000 cm -1 region – Dual scan experiment has allowed transfer of CH 4 standard to HCl – Positions may be improved to ~1x10 -5 cm -1 No (bandwide) self broadening or self shift parameters – TCCON calibration, common calibration for networked measurement system – Remote sensing for Venusian / Jovian / Saturnian chemistry LabFit exercise – Multispectrum lineshape fitting 6/16/2014MK10 HCl Overtone Lineshapes2

3. Band Selection http://hitran.iao.ru/survey/spectr 4800 5200 5600 6000 cm -1 Pubchem commons.wikimedia.org halo.wikia.com 6/16/2014MK10 HCl Overtone Lineshapes3

4. TCCON network The Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier Transform Spectrometers that record direct solar spectra in the near-infrared. From these spectra, accurate and precise column-averaged abundances of atmospheric constituents including CO 2, CH 4, N 2 O, HF, CO, H 2 O, and HDO, are retrieved. Calibrations are performed with sealed 10 cm 5mb HCl cells inside each interferometer Hase, F., B.J. Drouin, C.M. Roehl, G.C. Toon, P.O. Wennberg, D. Wunch, T. Blumenstock, F. Desmet, D.G. Feist, P. Heikkinen, M. De Maziere, M. Rettinger, J. Robinson, M. Schneider, V. Sherlock, R. Sussmann, Y. Te, T. Warneke, C. Weinzierl, Calibration of sealed HCl cells used for TCCON instrumental line shape monitoring, Atmos. Meas. Tech. 6(12), 3527-3537, 2013. ‘Narrowing’ effect is evident in Hase et al. http://www.tccon.caltech.edu/site-locations/index.html https://tccon-wiki.caltech.edu/ 6/16/2014MK10 HCl Overtone Lineshapes4

5. Remote Sensing of HCl Venus, solar occultation spectra, http://venus.aeronomie.be/en/soir/hcl.htm Goto et al. Earth Science: HALOE, ACE, MLS, Odin, ATMOS Mk IV, FIRS-2, SLS, (ALIAS in-situ) Also astronomy with: Spitzer, ISO, ATMOS, Odin, Herschel 6/16/2014MK10 HCl Overtone Lineshapes5

6. IFS- 125HR Bruker IFS-125HR at JPL ▪ The entire FTS enclousure evacuated to ~10 mTorr ▪ Maximum resolution, 0.0011 cm -1 ▪ Detectors and beamsplitters covering 20 - 15800 cm -1 ▪ Gas handling system with a 6″ Varian Turbo pump ▪ MKS Baratron pressure gauges up to 6.5 bar ▪ Hart Scientific PRT temperature sensors Various absorption gas cells ▪ Multipass White cell of (variable path length up to 32.5 m) ▪ Cryogenic cell (0.2 m long, developed by Dr. Arlan Mantz) ▪ Various single pass custom cells (from 2 cm to 26.5 cm) ▪ Very long path multipass White cell (~200 m) on the way Pressure scans in a joint tandem cell at 8 different pressures 6/16/2014MK10 HCl Overtone Lineshapes6

7. Experimental Two cells were used Long Path length (3.84 m) Short Path length (0.0614 m and 0.1526 m) (This goes inside the FTS) 6/16/2014MK10 HCl Overtone Lineshapes7

8. Calibration strategy Recent improvements in the metrology of CH 4 and C 2 H 2 have made the desired precision and accuracy attainable Absolute positions were determined with femtosecond laser spectroscopy Zolot, 2013 σ (MHz) σ (cm -1 ) 2.3 7.6E-05 1.0 3.3E-05 1.7 5.6E-05 2.5 8.3E-05 2.4 8.0E-05 1.2 4.0E-05 7.8 2.6E-04 1.3 4.3E-05 0.5 1.6E-05 1.2 4.0E-05 1.5 5.0E-05 0.8 2.6E-05 … … Zolot et al. JQSRT 118 (2013) 26-39 6/16/2014MK10 HCl Overtone Lineshapes8

9. Position Algorithm Information – Code in Matlab was written to analyze the spectra for line centers – Thresholding based on a ratio of intensity at the base of the peak and intensity at the peak was used as filtering criteria <5% of max intensity was not considered a peak – Peak picker uses zero filling, apodization, then spline interpolation between the bottom 3 points – Peak minimum finder based on 5 smoothing points and first and second derivative tests Position (cm -1 ) Residuals (cm -1 ) 6/16/2014MK10 HCl Overtone Lineshapes9

10. Line Centers Number MatchedMatch ThresholdStandard DeviationCal Factor 460.002210.000070091.00000093 400.000570.000035661.00000010 200.000120.000011201.00000003 80.000100.000008191.00000009 Matched values to the Zolot lines, goal was to improve the calibration error to be <2x10 -4 cm -1 We can get 1x10 -5 cm -1, sufficient precision and accuracy for use in OCO spectral analyses Precision was verified with quantum mechanical prediction software and had an RMS of ~7x10 -6 cm -1 6/16/2014MK10 HCl Overtone Lineshapes10

11. Pressure Broadening 1 st Pressure broadening and pressure shifts for entire v = 2-0 band Spectra taken in a dual chamber cell were used with CH 4 in one chamber as the calibrant and HCl in the other Pressures investigated were 10,15, 20, 25, 30, 40, 50 and 60 Torr 6/16/2014MK10 HCl Overtone Lineshapes11

12. Spectral Fitting no constraints Full Physics fits with LabFit to get pressure broadening and pressure shift 6/16/2014MK10 HCl Overtone Lineshapes12

13. Fitting Spectra with constraints Intensities with Honl-London Factors, exp(hv/kT), positions with B 0,B 2, D 0,D 2, H 0, H 2 6/16/2014MK10 HCl Overtone Lineshapes13

14. Linestrength – HITRAN On average 2.6% higher than HITRAN Both intensity and pressure broadening are consistently higher than HITRAN 6/16/2014MK10 HCl Overtone Lineshapes14

15. Isotopologues Comparison – Self Broadening 6/16/2014MK10 HCl Overtone Lineshapes15

16. Isotopologues Comparison – Self Shift 6/16/2014MK10 HCl Overtone Lineshapes16 The self-shift is not reported in HITRAN, nor any literature, yet it is critical to precisely calibrate the wavenumber of a spectrometer using typical HCl absorption pressure-pathlengths.

17. Isotopologues Comparison – Dicke 6/16/2014MK10 HCl Overtone Lineshapes17 The narrowing phenomenon is correlated with instrument variables such as resolution and aperture. The multispectrum fitting method allows a consistent retrieval over many pressures with these instrument variables fixed. The isotopologue comparison highlights the reproducible trend that has been separated from instrument variables.

18. Hamiltonian Parameters from constrained fit G(H35Cl) 5667.9824970 0.31266838505E-05 G(H37Cl) 5663.9268346 0.57468641899E-05 B"(H35Cl) 10.440189334 0.47834078032E-06 B"(H37Cl) 10.424502872 0.10281972891E-05 D"(H35Cl) 0.52805708530D-03 0.12479988598E-07 D"(H37Cl) 0.52645439847D-03 0.39573635036E-07 H"(H35Cl) 0.16600000000D-07 Fixed H"(H37Cl) 0.22900000000D-07 Fixed B'(H35Cl) 9.8345885033D+01 0.43757773938E-06 B'(H37Cl) 9.8202784918D+01 0.10900827192E-05 D'(H35Cl) 0.51541494165D-03 0.87793443626E-08 D'(H37Cl) 0.51416332228D-03 0.29243450328E-07 H'(H35Cl) 0.15400000000D-07 Fixed H'(H37Cl) 0.21300000000D-07 Fixed SQ/nu(H35Cl) 0.10469429511D-23 0.11154688922E-27 SQ/nu(H37Cl) 0.33157419710D-24 0.57034946781E-28 c1 (H35Cl) -.22686827401D-02 0.10987143469E-04 c1 (H37Cl) -.22476757421D-02 0.21406525775E-04 Guelachvili Opt. Comm. 19(1) 150-154, 1976 C 0 1 = -2.60(27)x10 -3, c 0 2 = -0.86(57)x10 -3 Tipping & Ogilvie JMS. 96 442-450, 1982 Toth et al. JMS. 35, 110-126, 1970 6/16/2014MK10 HCl Overtone Lineshapes18

19. Summary and Future Directions HCl spectra at multiple pressures have been analyzed simultaneously for lineshape parameters Low pressure scan has intensity issues, but should improve accuracy of positions 6/16/2014MK10 HCl Overtone Lineshapes19

20. Acknowledgements NASA ACLR OCO-2 ABSCO Linda Brown Keeyoon Sung Malathy Devi D. Chris Benner 6/16/2014MK10 HCl Overtone Lineshapes20 © 2014 California Institute of Technology. Government sponsorship acknowledged.

21. Pressure Broadening – HITRAN mSelf Width Self Width Error HITRAN Self Width Percent Difference from HITRAN -50.20880.00010.2131.9336 -40.23460.00010.2381.4042 -30.24390.00010.2420.7758 -20.23660.00010.2293.2751 0.220.00010.2133.2442 10.21310.00010.2015.9173 20.22460.00010.2154.3936 30.22990.00010.2242.6022 40.22230.00010.2181.9253 50.20160.00010.1972.2703 60.17520.00010.1693.6236 70.14840.00010.1396.6191 80.12690.00010.11114.0537 90.1080.00020.09612.2358 H 35 Cl mSelf Width Self Width Error HITRAN Self Width Percent Difference from HITRAN -40.23230.00020.2382.3542 -30.24200.00020.2420.0041 -20.23500.00020.2292.5926 0.21780.00030.2132.2151 10.21090.00030.2014.8610 20.22290.00020.2153.6072 30.22770.00020.2241.6368 40.22000.00020.2180.8793 50.19940.00020.1971.1825 60.17330.00020.1692.5010 70.14690.00030.1395.5937 80.12540.00040.11112.7785 90.10820.00060.09612.4713 H 37 Cl 6/16/2014MK10 HCl Overtone Lineshapes21

22. Linestrength – HITRAN mIntensity HITRAN intensityDifference percent difference -56.66E-216.38E-212.83E-224.44 -48.83E-218.44E-213.93E-224.66 -39.90E-219.46E-214.47E-224.73 -28.93E-218.53E-214.05E-224.74 5.46E-215.21E-212.45E-224.71 16.02E-215.75E-212.71E-224.71 21.09E-201.04E-204.84E-224.66 31.33E-201.27E-205.95E-224.69 41.31E-201.25E-205.78E-224.62 51.09E-201.04E-204.80E-224.61 67.90E-217.54E-213.54E-224.70 75.02E-214.80E-212.20E-224.59 82.83E-212.71E-211.20E-224.42 91.42E-211.37E-215.99E-234.39 mIntensity HITRAN intensityDifference percent difference -42.79E-212.69E-211.02E-223.79 -33.13E-213.02E-211.19E-223.93 -22.83E-212.72E-211.11E-224.08 1.72E-211.66E-216.32E-233.81 11.90E-211.83E-217.17E-233.92 23.44E-213.31E-211.36E-224.12 34.21E-214.05E-211.60E-223.94 44.14E-213.98E-211.56E-223.90 53.46E-213.32E-211.31E-223.95 62.50E-212.41E-218.77E-233.64 71.59E-211.54E-215.39E-233.51 88.96E-228.68E-222.83E-233.26 94.55E-224.37E-221.81E-234.15 H 35 Cl H 37 Cl 6/16/2014MK10 HCl Overtone Lineshapes22

23. Isotopologues Comparison – Line strengths PointRatio 23.16 3 4 53.17 63.16 73.17 83.16 9 103.15 113.17 123.16 133.16 143.12 6/16/2014MK10 HCl Overtone Lineshapes23