Waveguide ChirpedPulse Fourier Transform Microwave Spectra of 2

Astrochemistry of Alkylthiols • Few organosulfur compounds have been observed in the ISM. •

Chirped-Pulse Spectrometer 1 1) 2) 3) 1. 2. 3. 4. 5. Generate pulse Amplify

Senior Thesis Research 1 Worked with three previously studied small alkylthiols. High vapor pressures

Tunneling interactions in Et. SH 1 Thiol Potential Energy Scan in Et. SH 1

Tunneling interactions in 2 -Pr. SH 1 Thiol Potential Energy Scan in 2 -Pr.

2 -Propanethiol 1 2 million averages, 7 m. Torr, -20° C, 4 μs Fid

2 -Propanethiol: trans Conformer Expanded View 1 - Experimental - Simulated trans Lines Fit

2 -Propanethiol: gauche Conformer Expanded View 1 Lines Fit RMS (k. Hz) Max J

g-2 -Pr. SH Splitting 743 Transition ← 734 (+ -) (- +) Frequency (MHz)

Results g-2 -Pr. SH Hamiltonian: Ĥ = Ĥ+++ Ĥ-- + Ĥ+- • Ĥ++ =

Conclusions and Future Work • 391 (41%) of the 964 peaks have been assigned

Acknowledgments 1 • • Professor Shipman Ben Rooks Maria Phillips Christian Metzger Ian Finneran

The Galactic Centre and Sagittarius B 2, from the European Southern Observatory http: //www.

Laboratory improvements: 18 -26. 5 GHz Spectrometer • Our previous frequency range was 8.

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Waveguide Chirped-Pulse Fourier Transform Microwave Spectra of 2 -Propanethiol Bri Gordon Steven T. Shipman New College of Florida

Astrochemistry of Alkylthiols • Few organosulfur compounds have been observed in the ISM. • Methanethiol has been observed in Sagittarius B 2. * *Linke, R. A. ; Frerking, M. A. ; Thaddeus, P. ; Astrophysical Journal 234, L 139 (1979). • Larger alkylthiols may be present; existing fits should be extended in order to search for them in the ISM.

Chirped-Pulse Spectrometer 1 1) 2) 3) 1. 2. 3. 4. 5. Generate pulse Amplify pulse Send pulse to waveguide Amplify molecular emission Record, average emission in the time domain 6. Fourier transform the emission 4) 5), 6) Chirped Pulse (Linear Frequency Sweep)

Senior Thesis Research 1 Worked with three previously studied small alkylthiols. High vapor pressures and strong dipoles: g-Et. SH 0 cm-1 • 2 -propanethiol DFT B 3 LYP / 6 -311++G(d, p) t-Et. SH 213. 3 cm-1 1 • Ethanethiol • 1 -propanethiol g'-Et. SH 0 cm-1 TG-1 -Pr. SH 0 cm-1 TG’-1 -Pr. SH 0 cm-1 t-2 -Pr. SH 0 cm-1 g-2 -Pr. SH 41. 3 cm-1 TT-1 -Pr. SH 249. 5 cm-1 1 g’-2 -Pr. SH 41. 3 cm-1

Tunneling interactions in Et. SH 1 Thiol Potential Energy Scan in Et. SH 1 trans gauche' gauche trans The thiol H-atom tunneling through the potential barrier • The tunneling induces symmetric and antisymmetric states. • c - type transitions between these states are split by as much as 3. 5 GHz. V 2 V 3 Previous* Ab Initio** -135 (27) 456. 4 (20) -152. 28 (18) 451. 68 (17) *Nakagawa, J. , Kuwada, K. , Hayashi, M. Bull. Chem. Soc. Jpn. 49, 3420 (1976). **DFT B 3 LYP/6 -311++G(d, p)

Tunneling interactions in 2 -Pr. SH 1 Thiol Potential Energy Scan in 2 -Pr. SH trans gauche' gauche 1 trans b - type transitions between states show tunneling splitting *Griffiths, J. H. J. Mol. Spec. , 56, 257 (1975). Previous* Ab Initio** V 2 - 47. 74 (14. 4) V 3 657. 54 489. 44 (13. 4) **DFT B 3 LYP/6 -311++G(d, p)

2 -Propanethiol 1 2 million averages, 7 m. Torr, -20° C, 4 μs Fid - Experimental Simulated trans Simulated gauche 964 peaks above the 3: 1 signal to noise threshold (D) trans* µa 1. 75 µb 0. 004 µc 0. 38 µtot 1. 80 (D) gauche* µa 1. 52 µb 0. 70 µc 0. 70 µtot 1. 81 *DFT B 3 LYP / 6 -311++G(d, p)

2 -Propanethiol: trans Conformer Expanded View 1 - Experimental - Simulated trans Lines Fit RMS (k. Hz) Max J Previous* Current 12 50 4 126 69 80 a – type b – type c – type *Griffiths, J. H. ; J. Mol. Spec. , 56, 257 (1975). # of Lines 78 48

2 -Propanethiol: gauche Conformer Expanded View 1 Lines Fit RMS (k. Hz) Max J - Previous* 55 50 5 Current 265 112 42 a – type b – type c – type Experimental Simulated gauche # of Lines 96 73 96 *Griffiths, J. H. ; J. Mol. Spec. , 56, 257 (1975). Max Splitting (MHz) 107. 6 1124. 6 91. 7

g-2 -Pr. SH Splitting 743 Transition ← 734 (+ -) (- +) Frequency (MHz) 22229. 60 23279. 61 Splitting (MHz) 1050. 01

Results g-2 -Pr. SH Hamiltonian: Ĥ = Ĥ+++ Ĥ-- + Ĥ+- • Ĥ++ = A+ Ĵa 2 + B +Ĵ b 2 + C +Ĵ c 2 • Ĥ-- = A–Ĵa 2 + B–Ĵb 2 + C–Ĵc 2 + ∆ν • Ĥ+- = Fa (ĴbĴc + ĴcĴb) + Gc (iĴc) + Fc (ĴaĴb + ĴbĴa) * DFT B 3 LYP/6 -311++G(d, p) A (MHz) B (MHz) C (MHz) ∆v (MHz) Fa (MHz) Gc (MHz) Fc (MHz) DJ (k. Hz) DJK (k. Hz) DK (k. Hz) d. J (k. Hz) d. K (k. Hz) ФKJ (HZ) Lines Fit RMS (k. Hz) Ab Initio* 7822. 81 4417. 69 3106. 01 1. 5 2. 4 2. 6 0. 44 3. 3 - gauche Current 7873. 82 (12) 4528. 44 (11) 3172. 567 (8) 562. 259 (21) 60. 321 (29) 8. 19 (22) 145. 33 (132) 1. 454 (35) 2. 344 (62) 2. 97 (16) 0. 453 (4) 3. 390 (47) 265 112 Ab Initio* 7831. 54 4319. 54 3096. 80 1. 3 2. 7 2. 4 0. 37 2. 8 - trans Current 7892. 410 (8) 4414. 444 (7) 3158. 072 (7) 1. 3 (fixed) 2. 61 (12) 2. 77 (33) 0. 366 (7) 2. 997 (92) 0. 0481 (7) 126 69

Conclusions and Future Work • 391 (41%) of the 964 peaks have been assigned to the trans and gauche ground state normal species. • Next spectra to fit are vibrationally excited states and 34 S species

Acknowledgments 1 • • Professor Shipman Ben Rooks Maria Phillips Christian Metzger Ian Finneran Ben Reinhold New College of Florida The National Science Foundation This material is based upon work supported by the National Science Foundation Division of Chemistry under Grant No. 1111101 (co-funded by MPS/CHE and the Division of Astronomical Sciences).

The Galactic Centre and Sagittarius B 2, from the European Southern Observatory http: //www. eso. org/public/images/eso 0924 e/

Laboratory improvements: 18 -26. 5 GHz Spectrometer • Our previous frequency range was 8. 7 - 18. 3 GHz • A new circuit was built to extend it to 26. 5 GHz (left).

2 -Propanethiol 1 2 million averages, 7 m. Torr, -20° C, 4 μs Fid 964 peaks above the 3: 1 signal to noise threshold