Molecular Spectroscopy Symposium June 2011 ROTATIONAL SPECTROSCOPY OF HD 18 O John C. Pearson, Shanshan Yu, Harshal Gupta, and Brian J. Drouin, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109

2 Molecular Spectroscopy Symposium June 2011 Why HD 18 O? Trace constituent of the Earth’s Atmosphere –ODIN satellite detected it in the limb of the Earth’s atmosphere Interesting physics –Watson Hamiltonian has convergence problems for water –Separation of rotation and vibration begins to fail at K>9  Available spectrum extensively critically review –Tennyson et al., 2010, JSQRT 111, 2160 –Mikhailenko et al., 2009, JSQRT 110, 597  Are the levels as good as claimed? The Herschel HIFI Orion Surprise –H 2 O, H 2 18 O, H 2 17 O & HDO can all be optically thick!! –Rotational transitions of HD 18 O are detected  Thankfully they are not optically thick

3 Molecular Spectroscopy Symposium June 2011 Herschel HIFI Orion Spectra HDO is Optically Thick!!! HD 18 O is 10% of HDO in Red component optical depth this component is  ~50 i.e. a lot of water

4 Molecular Spectroscopy Symposium June 2011 Previous Work One microwave study (27 lines) –From Steenbeckeliers published by F. Lovas, 1978, J. Chem. Phys. Ref. Data 7, 1445 Several IR studies of ground state at 2 band –J.W. Fleming & M.J. Gibson, 1976, JMS 62, 326 (16-34 cm -1 ) –J.W.C. Johns, 1985, J. Opt. Soc. Am. B 2, 1340 (20-350cm -1 ) –R.A. Toth, 1993, JMS 162, 20 ( 2 band) –A.-W. Liu et al., 2006, JMS 237, 149 ( 2 band) –A.-W. Liu et al., 2011, JMS 265, 26 ( 2 band) All but the most recent were part of the critical review –Predicted accuracy from MARVEL deserved a test

5 Molecular Spectroscopy Symposium June 2011 Experimental The direct multiplication spectrometer at JPL was utilized for most measurements Multiplication factors up to 162 were utilized (to 2.72 THz!!!) Transitions between 530 and 660 were measured with a phase locked BWO at JPL Measurements were performed on a 50/50 H 2 O/D 2 O sample with 18 O in “natural” abundance –There appeared to be a slight enhancement of 18 O in presumably from the D 2 O –Only the ground state strong lines were attempted

6 Molecular Spectroscopy Symposium June 2011 Some Example Lines 1(1,0)-1(0,1) 4(1,3)-4(0,4) 6(0,6)-5(0,5) 8(3,6)-8(2,7)

7 Molecular Spectroscopy Symposium June 2011 Data 51 new microwave accuracy transitions –Accuracy kHz –Measurements between 453 and 2718 GHz –Highest J is 10 (previous data was 12) –Highest K is 6 (previous data was 5) 27 previous microwave transitions 3031 Infrared transitions ( & ) –All not rejected by MASTER review (~20 more weighted out) –All from Liu et al (~50 weighted out)  Some oblate paired doublets and quartets added –Highest J is 19 in 010, 18 in 000 –Highest K is 11 in 010, 10 in 000

8 Molecular Spectroscopy Symposium June 2011 Levels connected with microwave measurements This work Previous

9 Molecular Spectroscopy Symposium June 2011 Analysis Analyzed the spectrum using Euler Series Hamiltonian –Pickett, Pearson, & Miller, 2005, JMS 233, 174. {,} is an anti-commutator. The a’s and b’s are parameters (manually adjusted)

10 Molecular Spectroscopy Symposium June 2011 Potential Problems 1/4 GS K=9 010 J(0,J), GS K= J(1,J-1), J=11

11 Molecular Spectroscopy Symposium June 2011 Potential Problems 2/4 GS K= J=12 GS K= J(4, J=15

12 Molecular Spectroscopy Symposium June 2011 Potential Problems 3/4 GS K= K=8 100 J(0,J), 16

13 Molecular Spectroscopy Symposium June 2011 Potential Problems 4/4 010 K=8 100 J(1,J-1), GS K= J=14

14 Molecular Spectroscopy Symposium June 2011 Problematic Levels Six lines were identified in the infrared data set that showed local perturbations –010 15(4,12) & (4,13) levels are slightly perturbed Liu et al., 2011 data did not properly blend the oblate paired high J lines –Adding the omitted a- and b-type transitions in the blended lines improved the fit Most weighted out lines were weak and their “badness” was supported by other measurements of the same level. 68 constants used to fit all 34 in 000, 34 in 010 Reduced RMS is (with about 70 rejected lines out of 3000) –All the microwave data fits to 3 sigma

15 Molecular Spectroscopy Symposium June 2011 Constants Diagonal Parameters value value b_Jx a_Kx b'_Jx a'_Kx Constant Value MHz Uncert. value MHz Uncert. E (B+C)/ A-(B+C)/ D 0, D 1, D 2, D 0,3 x D 1, D 2, D 3, D 0,4 x D 1,3 x D 2,2 x D 3,1 x D 4,0 x D 1,4 x D 2,3 x fixed D 3,2 x D 4,1 x D 5,0 x D 6,0 x

16 Molecular Spectroscopy Symposium June 2011 Constants Off-Diagonal Constant Value MHz Uncert. value MHz Uncert. (B-C)/ d 0, d 1, d 0,2 x d 1, d 2, d 0,3 x fixed d 1,2 x d 2,1 x d 3,0 x d 1,3 x fixed d 2,2 x d 2,3 x d 4,0 x d 5,0 x

17 Molecular Spectroscopy Symposium June 2011 Conclusions 51 Transitions of HD 18 O were measured to microwave accuracy Approximately 70 lines of suspicious accuracy were identified in the infrared data set One local perturbation involving 000 K=11 and 010 K=4 was identified at J=15 and J=16 Transitions frequencies for the ground state of HD 18 O can be calculated to microwave accuracy for J<10, K<7.

18 Molecular Spectroscopy Symposium June 2011 Acknowledgement This research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. NASA support for Herschel Heterodyne Instrument for Far Infrared guaranteed time holders is gratefully acknowledged. © 2011 California Institute of Technology all rights reserved