THz Spectroscopy of 1d-ethane: Assignment of v18

ADAM M. DALY, BRIAN J. DROUIN, LINDA BROWNJet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109

PETER GRONERDepartment of chemistry , University of Missouri, Kansas City, MO.

18-Jun14 ISMS FE07

ISMS FE07

Motivation

18-Jun14

A window in the ethane spectrum? Avoiding q-branch ethane

• Astronomy

http://universe-review.ca/F07-planets06.htm

ISMS FE07

Motivation

18-Jun14

Assign v11= 715 cm-1 and v17 = 805 cm-1

in C2H5D and fit transitions to within the resolution of the measurement

Data taken with the Bruker 125 HR with 20.8 m path length.

Resolution 0.0028 cm-1

Temperature = 130 K

• Spectroscopy v11= 715 cm-1 v17 = 805 cm-1

4v18= 726 cm-1?

ISMS FE0718-Jun14

Motivation

v11= 715 cm-1 (A’) and v17 =805 cm-1(A”)

Dark state, 3 v18 at 726 cm-1 (A”)

ISMS FE07

Motivation

18-Jun14

• Spectroscopy

Assign v11= 715 and v17 = 805 in C2H5Dand fit transitions to within the resolution of the measurement

Data taken with the Bruker 125 HR with 20.8 m path length.

Resolution 0.0028 cm-1

Temperature = 130 K

v11= 715 v17 = 805

ISMS FE07

Motivation

18-Jun14

v17 = 715 in C2H5D

High Kc R-branch

v11= 715Q-branch Ka upper andLower zero

• Spectroscopy J1,J-1 ← J0,JJ0,J ← J1,J-1

ISMS FE07

Motivation

18-Jun14

• SpectroscopyA E A E A E A E A E A E A E

J1,J-1 <- J0,J1 2 3 4 5 6 7

30,2 <- 20,1

J=61,6 <- 52,3

v11= 715Q-branch Ka lower zero

ISMS FE07

Motivation

18-Jun14

• Spectroscopy v11= 715 v17 = 805

v17 = 805

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Motivation

18-Jun14

• Spectroscopy4←3 5←4 6←5 7←6 8←7 9←8Ka”←Ka’v17 = 805

Q-branch Ka -> Ka+1

ISMS FE07

Motivation

18-Jun14

Clearly split by internal rotation

• Spectroscopy 152,13←141,13 161,15←150,15

v17 = 805

Q-branch Ka = 7 ← Ka= 6

111 8 J21 20 19 18 17 16 15 14 13 12 11 10 9 8 7

ISMS FE07

Background

18-Jun14

D

H

HH

H

H

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)

TB03 OSU Conference 2013

BRIAN J. DROUIN, SHANSHAN YU, JOHN C. PEARSON, LINDA R. BROWN, KEEYOON SUNG, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109; PETER GRONER, Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110-2499. • The data set contains two Q-branch measurements (K = 5-6 and K = 9,10 , the first

with J up to 30) and a smattering of R-branch measurements up to J = 28 and K’s in the teens.

• There are 475 unique assignments, but many of these are for blended features.

ISMS FE07

Methods

18-Jun14

Ground state results

ISMS FE0718-Jun14

Experimental Setups

520-605, 680-800, 960-1240 GHz, 6 meter path, 1.2 K Silicon Bolometer, Static cell with amorphous quartz windows

MultiplierInlet Port Vacuum Port

Glass Cell 3m

RooftopReflector

Bolometer

Polarized Grid

Stanford Research Lock-in Amplifier

Preamp

16.78888 Ghz

Synthesizer

GPIB

ISMS FE0718-Jun14

Initial scans

ISMS FE0718-Jun14

Initial scans

ISMS FE0718-Jun14

Initial scans

ISMS FE0718-Jun14

Initial scans

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Initial Scans

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Initial Scans

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ERHAM SPFITPure 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)

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)

q / kHz -402.3(76) -640.2(85)

] q / kHz

45.3(64) -21.99(94)

/kHz

-30.9(31) -116.98(51)

/ kHz

0.569(46) -33.4(16)

] / kHz

-1.48(37) -

/kHz 2.83(19) -

/kHz 0.00283(19) 0.00346(36) /kHz - 0.00231(37) /kHz - -0.00151(21) /kHz .305(34) 0.286(81) /kHz - -58(20) /kHz -0.00134(49) -0.00154(27)

/kHz -0.0333(57) 0.080(31)

/kHz - 7.5(35) /kHz - -0.00154(27) /kHz - -0.000309(26)

/mHz - -Dab / kHz 1693.(202) -

Final fit of v18

TORSIONAL ENERGY DIFFERENCES (MHz)

v18 (A-E) = -3381.8516 +/- 0.2667

v18 fitState 00: 163 lines MICROWAVE RMS = 0.268358 RMS ERROR = 1.130830 State 10: 164 lines MICROWAVE RMS = 0.349844 RMS ERROR = 1.344719

ISMS FE0718-Jun14

ERHAM SPFITPure 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)

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)

q / kHz -402.3(76) -640.2(85)

] q / kHz

45.3(64) -21.99(94)

/kHz

-30.9(31) -116.98(51)

/ kHz

0.569(46) -33.4(16)

] / kHz

-1.48(37) -

/kHz 2.83(19) -

/kHz 0.00283(19) 0.00346(36) /kHz - 0.00231(37) /kHz - -0.00151(21) /kHz .305(34) 0.286(81) /kHz - -58(20) /kHz -0.00134(49) -0.00154(27)

/kHz -0.0333(57) 0.080(31)

/kHz - 7.5(35) /kHz - -0.00154(27) /kHz - -0.000309(26)

/mHz - -Dab / kHz 1693.(202) -

Final fit of v18

Ground stateState 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

v18 fitState 00: 163 lines MICROWAVE RMS = 0.268358 RMS ERROR = 1.130830 State 10: 164 lines MICROWAVE RMS = 0.349844 RMS ERROR = 1.344719

ISMS FE0718-Jun14

Table 3. Potential parameters in cm-1, relative to the potential minimum, F was fixed at 28259 MHz.

Parameter Hirota* Fernandez* All V3 1009.5 1005.8(37) 1003.50(7) V6 - 7.(3) 7.26(33) *values derived from spectral line positions reported in these studies

Table 4. Torsional levels in cm-1 relative to the zero-point energy based on potential fit parameters in Table 3.

Level Hirota* Fernandez* All 4(A) 269.46 271.51 271.11 4(E) 269.57 271.62 271.22 24(E) 510.91 513.32 512.54 24(A) 512.91 515.38 514.62 34(A) 714.12 715.16 713.98 34(E) 732.98 734.72 733.68 44(E) 849.25 847.96 846.44 44(A) 904.87 904.51 903.16 *values derived from spectral line positions reported in these studies

Using the ground state, v18 and Raman data

E. Hirota, Y. Endo, S. Saito, J.L. Duncan, Microwave spectra of deuterated ethanes: Internal rotation potential function and rz structure, J. Mol. Spectrosc. 89 (1981) 285–295. doi:10.1016/0022-2852(81)90024-2.J,M. Fernandez and S. Montero, J. Chem. Phys. 94, 7788 (1991)

ISMS FE07

Potential Fit

18-Jun14

-200 -150 -100 -50 0 50 100 150 2000

200

400

600

800

1000

1200

656 cm-1

654 cm-1

413.3 cm-1

413.2 cm-1

142.06 cm-1

142.08 cm-1

875 cm-1

856 cm-1

G.S.

vt=1.

vt=2.

vt=3.

ISMS FE07

Conclusions: Future directions from TB03 (2013)

18-Jun14

• Retrieved positions and intensities up to 860 cm-1 (done)– Challenging spectrum 9000 features 700-850 cm-1

• Complete assignments IR spectrum in 700 - 860 cm-1 range • to v11, v17 and perhaps 3vt (overtone) (in progress)• Develop Effective Hamiltonian and model observed positions and

intensities (in progress)• Create a linelist to enable the first detection of this species in

outer planets. (in progress)

ISMS FE0718-Jun14

Acknowledgements

• Brian Drouin• Linda Brown• John Pearson• Peter Groner