The n17 band of C2H5D from 770-880 cm-1 ADAM M. DALY1, BRIAN J. DROUIN1, JOHN C. PEARSON1, KEEYOON SUNG1, LINDA R. BROWN1, ARLAN MANTZ2, MARY ANN H. SMITH3 1Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 2Dept. of Physics, Astronomy and Geophysics, Connecticut College, New London, CT 06320, 3Science Directorate, NASA Langely Research Center, Hampton, VA 23681 23-Jun-15 ISMS TG-01

Planetary atmospheres Motivation Planetary atmospheres http://universe-review.ca/F07-planets06.htm Utilize bold and use the largest size that makes sense A window in the ethane spectrum? Avoiding q-branch ethane 23-Jun-15 ISMS TG-01 C2H5D C2H6

Background – Infrared, Raman and Submillimeter Correspondence table of vibrational states of ethane isotopologues C2H6 Band Center cm-1 13CH312CH3 12C2H5D n12(E2d) 1196.9 [1] n11 ~1198 [est.] n16(A″) 1158 [5] n9 (A′) 1121 [5] n 9(E1d) 821.7224 [2] n12 821.5 [4] n17(A″) 805.3420[this work] n11(A′) 715. [5] n 4 289.52 [3] n6 289 [4] n18(A″) 271.1 [6] [1] J.M. Fernández, S. Montero,, J. Chem. Phys. 118 (2003) 2657-2672. [2] L. Henry, A. Valentin, W.J. Lafferty, J.T. Hougen, V.M. Devi, P.P. Das, K.N. Rao,, J. Mol. Spectrosc. 100 (1983) 260-289 [3] J.M. Fernández‐Sánchez, A.G. Valdenebro, S. Montero,. J. Chem. Phys. 91 (1989) 3327-3334. [4] L. Borvayeh, N. Moazzen-Ahmadi, V.M. Horneman, J. Mol. Spectrosc. 255 (2009) 157-163. [5] L.R. Posey, Jr., E.F. Barker,, J. Chem. Phys. 17 (1949) 182-187. [6] A.M. Daly, B.J. Drouin, P. Groner, S. Yu, J. Pearson,, J. Mol. Spectrosc. 307 (2015) 27-32. 23-Jun-15 ISMS TG-01

Background Spectroscopy Assign n11= 715 cm-1 and n17 = 805 cm-1 v11= 715 cm-1 v17 = 805 cm-1 Assign n11= 715 cm-1 and n17 = 805 cm-1 in C2H5D and fit transitions to within the resolution of the measurement Data taken with the Bruker 125 HR with 20.38 cm path length. Resolution 0.0028 cm-1 Temperature = 130 K 3v18= 726 cm-1? Fix the units 23-Jun-15 ISMS TG-01

Background Spectroscopy v17 = 805 Q-branch Ka -> Ka+1 23-Jun-15 152,13←141,13 161,15←150,15 111 8 J21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 4←3 5←4 6←5 7←6 8←7 9←8 Ka”←Ka’ 23-Jun-15 ISMS TG-01

Background – pure rotational Microwave spectra of deuterated ethanes: Internal rotation potential function and rz structure E. Hirota, Y. Endo, S. Saito, J.L. Duncan, J. Mol. Spectrosc. 89 (1981) 285–295. Pure a-dipole 12 pairs A/E 2 R-branch (J=3 and 4) b-dipole 15 pairs A/E that 2 R-branch (J=2 and 3) and 13 Q-branch (Ka 2<- 1) D H Analysis of the rotational spectrum of the ground and first torsional excited states of monodeuterated ethane, CH3CH2D Adam M. Daly, Brian J. Drouin, Peter Groner, Shanshan Yu, John Pearson J. Mol. Spectrosc. 307 (2015): 27-32 Measured up to 1600 GHz Spectroscopic constants have been fit to 984 transitions in the ground state 422 transitions in the first torsional excited state (ν18) SPFIT, ERHAM and XIAM and of the first torsional state with SPFIT and ERHAM Looking along the c-c bond 23-Jun-15 ISMS TG-01

Background ISMS FE07 - 2014 Ground state results 23-Jun-15 ISMS TG-01

Background: Final fit of v18 Tunneling terms ERHAM  SPFIT  2*e10 /MHz 2253.10(22) 2252.62(24) 2*e20 /MHz 0.471(16) 1.509(58) r 0.4343990(81) [ 0.434401021] b / deg   0.873(75) [𝐴− 𝐵+𝐶 2 ]q / kHz -402.3(76) -640.2(85) [ 𝐵+𝐶 2 ] q / kHz 45.3(64) -21.99(94) 𝐵−𝐶 4 q /kHz -30.9(31) -116.98(51) 𝐴− 𝐵+𝐶 2 𝑐𝑜𝑠 2 𝜌𝜎𝐾 / kHz 0.569(46) -33.4(16) [ 𝐵+𝐶 2 ] 𝑐𝑜𝑠 2 𝜌𝜎𝐾 / kHz -1.48(37) - 𝐵−𝐶 4 𝑐𝑜𝑠 2 𝜌𝜎𝐾 /kHz 2.83(19) 𝑑 2 𝑐𝑜𝑠 𝜌𝜎𝐾 /kHz 0.00283(19) 0.00346(36) 𝑑 2 𝑐𝑜𝑠 2 𝜌𝜎𝐾 /kHz 0.00231(37) 𝑑 2 𝑐𝑜𝑠 3 𝜌𝜎𝐾 /kHz -0.00151(21) 𝐷 𝐾 𝑐𝑜𝑠 𝜌𝜎𝐾 /kHz .305(34) 0.286(81) 𝐷 𝐾 𝑐𝑜𝑠 3 𝜌𝜎𝐾 /kHz -58(20) 𝐷 𝐽 𝑐𝑜𝑠 𝜌𝜎𝐾 /kHz -0.00134(49) -0.00154(27) 𝐷 𝐽𝐾 𝑐𝑜𝑠 𝜌𝜎𝐾 /kHz -0.0333(57) 0.080(31) 𝐷 𝐽𝐾 𝑐𝑜𝑠 3 𝜌𝜎𝐾 /kHz 7.5(35) 𝐻 𝐽𝐽𝐾 𝑐𝑜𝑠 𝜌𝜎𝐾 /kHz 𝐻 𝐽𝐽𝐾 𝑐𝑜𝑠 2 𝜌𝜎𝐾 /kHz -0.000309(26) 𝐻 𝐾 𝑐𝑜𝑠 𝜌𝜎𝐾 /mHz Dab / kHz 1693.(202)   ERHAM SPFIT Pure Rotation A /MHz 69633.185(10) 69633.176(17) B /MHz 18774.4219(20) 18774.4207(21) C /MHz 18164.4825(20) 18164.4812(19) DJ /kHz 26.6122(24) 26.6099(10) DJK /kHz 68.538(33) 68.469(46) DK /kHz 241.69(12) 241.35(28) d1 /kHz -0.92184(67) -0.92106(81) d2 /kHz 0.12141(55) 0.12285(46) HJ /Hz -0.0055(28) - HJK /Hz 0.175(30) 0.158(27) HKJ /Hz 1.53(25) 0.31(28) HK /Hz -8.76(134) v18 fit State 00: 163 lines MICROWAVE RMS = 0.268358 RMS ERROR = 1.130830 State 10: 164 lines MICROWAVE RMS = 0.349844 RMS ERROR = 1.344719 Ground state State 00: 298 lines MICROWAVE RMS = 0.214684 RMS ERROR = 0.900575 State 10: 469 lines MICROWAVE RMS = 0.334478 RMS ERROR = 0.952100 TORSIONAL ENERGY DIFFERENCES (MHz) ground state (A-E) = 74.1616 +/- 0.0366 MHz v18 (A-E) -3381.8516 +/- 0.2667 MHz ISMS TG-01 23-Jun-15

AABS1 prediction using n18 model Gave us hope that the problem could be solved using SPFIT 1Z.Kisiel, L.Pszczolkowski, I.R.Medvedev, M.Winnewisser, F.C.De Lucia, E.Herbst, J.Mol.Spectrosc. 233,231-243(2005) http://info.ifpan.edu.pl 23-Jun-15 ISMS TG-01

Starting point – Least squares retrieval* Line position and intensity for every feature found above the noise level from 700-900 cm-1 Over 10,000 features were Measured and fit using LSR Covering n11, n17, C2H6 (2%) Be specific about algorithm *L.R. Brown, J.S. Margolis, R.H. Norton, B. Stedry, Appl. Spectrosc. 37 (1983) 287–92. 23-Jun-15 ISMS TG-01 C2H5D C2H6

Building the Hamiltonian in SPFIT The substates A and E corresponding to s=0, ±1 have differing Fourier coefficients which are 1:− 3 2 : 1 2 , 1:− 1 2 :− 3 2 , 1:1 for terms of powers of cosn(t),where 𝜏= 2𝑛𝜋 3 (𝜎+𝜌Κ) and n is 1,2,3 respectively. Initial assignments were generated in the AABS program with the built in line center algorithm. Eventually, inclusion of 5035 transitions in the model. 23-Jun-15 ISMS TG-01

Spectroscopic Constant 12C2H5D Hamiltonian Constants for n17 with ground state parameters fixed Spectroscopic Constant Ground state n17 *   ‘v’ 805. 342729(27) A/ cm-1 [ 2.323387] 2.3410517(13) B/ cm-1 [ 0.62907126] 0.62720325(29) C/ cm-1 [0.60755897] 0.60681418(29) DJ / cm-1 × 106 [ 0.89672261] 0.88920(36) DJK / cm-1 × 106 [ 2.214256] 1.9877(22) DK / cm-1 × 106 [ 8.1759858] 10.182(14) d1 / cm-1 × 109 [-33.733216] -30.19(10) d2 / cm-1 × 109 [ 2.755709] 2.050(58) HJ / cm-1 × 1012 [ 0.15081306] 0.60(18) HJK / cm-1 × 1012 [6.5322758] - HKJ / cm-1 × 1012 [ -] -143.(15) HK / cm-1 × 1012 [149.23897] -441.(40) Tunneling Constants** e1 cos(t) / cm-1 × 103 [-1.6511214] 5.376(23) e2 cos2(t) / cm-1 × 103 [ 0.0022156424] 1.513(23) e3 cos3(t) / cm-1 × 103 0.197(22) 𝐴− 𝐵+𝐶 2 cos(t) / cm-1 × 106 [-0.276817895] (𝐵+𝐶) 2 cos(t) / cm-1 × 106 [0.004816287] -0.718(53) (𝐵+𝐶) 2 cos2(t) / cm-1 × 106 -0.606(53) (𝐵+𝐶) 2 cos3(t) / cm-1 × 106 -0.233(46) (𝐵−𝐶) 4 .cos(t) / cm-1 × 106 [0.093468757] -0.249(54) (𝐵−𝐶) 4 . cos2(t) / cm-1 × 106 -1.973(51) r [0.434361174]* [0.424701021] N / Nrejected by fit 5035 / 0 sfit / cm-1 0.00070 sRMS 1.00 J″min ̶ J″max 0 ̶ 40 K″a min ̶ K″a max 0 ̶ 18 Uncertainty of the transitions were determined As follows: For line positions within two orders of magnitude of the Strongest predicted feature: 0.000375 cm-1 and 0.000750 cm-1 if predicted weaker. The spectrum contained many blended features arising from C2H5D or the 2% contamination of C2H6. The number of these features within a ±0.005 cm-1 window was multiplied by the uncertainty (n+1) giving a total uncertainty for each line All assigned features above the noise limit were accepted in the model 23-Jun-15 ISMS TG-01

Some issues with line positions Presence of n9 2% C2H6 in the R-branches Presence of n11 in the P-branches 23-Jun-15 ISMS TG-01

Results Spectrum taken 130K Prediction made at 296K Correct transition dipole and partition function needed to predict the intensity 23-Jun-15 ISMS TG-01

Partition Function and transition dipole Rotation-vibration partition function computed with the ground and five vibrational states v18, 2v18, 3v18, v11 and v17. Temperature (K) Qtot 9.375 129 18.75 359 37.5 1009 75.0 130.5 2858 6871 150 8698 225 18267 296 31812 300 32721 Initial work found a transition moment of 40.28 x 10-3D. 2v18, 3v18 rotational constants taken from fit of gs and v18 Energy levels from the fit with ASTOR n11 from our best fit to date 23-Jun-15 ISMS TG-01

Checking with room temp spectrum Each lab spectrum (in black)with the room temperature prediction using partition function and transition dipole with a correction Pathlength=20.38cm Pressure:16.13 Torr Temp=296K Resolution:0.0028 cm-1 Gas conditions 23-Jun-15 ISMS TG-01

Not everything is perfect with line position but intensity prediction is very good Prediction in intensity and line position Prediction in intensity, line position fit Small (+0.005 cm-1 bias in this q-branch, Ka 0→ 1) similar in other K’s 23-Jun-15 ISMS TG-01

Distortion constant on the transition dipole A value of be -0.003D was added to the dipole moment containing the term 𝑀 5 =𝑖( 𝜇 𝑐 ′ , 𝐽 𝑎 + 𝜇 𝑎 ′ , 𝐽 𝑐 /2 and coded with 50003 (state 0 is gs, 3 is n17) 23-Jun-15 ISMS TG-01

Conclusions The n17 band of C2H5D has been fit to an effective Hamiltonian using SPFIT Spectroscopic terms have been found that predict line positions and intensities. A small but observable bias exists in the frequency residuals as a function of K that can not accounted for in the present analysis Future Work: n11 fit 23-Jun-15 ISMS TG-01

Acknowledgements Linda R. Brown Keeyoon Sung Brian J. Drouin John C. Pearson Peter Groner Arlan Mantz Mary Ann H. Smith Tim Crawford California Institute of Technology Jet Propulsion Laboratory 23-Jun-15 ISMS TG-01