1. Xinxin Cheng, Yao Zhang, Michael P. Minitti, Sanghamitra Deb, James Budarz, Peter M. Weber Chemistry Department Brown University 66 th OSU International Symposium on Molecular Spectroscopy 06/21/2011 Ultrafast Structural Dynamics of Tertiary Amines upon Electronic Excitation

2. Response to Electronic Excitation: Ammonia Ground State David M. Bishop, J. C. Leclerc and Y. Takahata, Journal of Molecular Spectroscopy, 1971, 39, 79-89 Halpern, A. M.; Roebber, J. L.; Weiss, K. J. Chem. Phys. 1968,49, 1348–1357 Excited State laser pulse

3. Tertiary Amines Ground State Halpern, A. M.; Roebber, J. L.; Weiss, K. J. Chem. Phys. 1968,49, 1348–1357 ? Issues in tertiary amines: Steric hindrance Conformers Intramolecular vibrational redistribution(IVR)

4. What is the structural response of tertiary amines to electronic excitation? Can we measure it? Observe the structure as a function of time. Question to Ask and Our Goal

5. Rydberg Fingerprint Spectroscopy Xiao Liang, Michael G. Levy, Sanghamitra Deb, Joseph D. Geiser, Richard M. Stratt*, Peter M. Weber,*Journal of Molecular Structure 978 (2010) 250–256 n: principle quantum # δ: quantum defect

6. 5 KHz Rep. Rate Two color experiment 4ω+2ω 208 nm pump (5.96 eV) 416 nm probe (2.98 eV) 5 KHz Rep. Rate Two color experiment 4ω+2ω 208 nm pump (5.96 eV) 416 nm probe (2.98 eV) Jie Bao, Dissertation, 2011, page 10 Experimental Settings

7. PES 4ω+2ω A typical two-color PES of amine Jaimie L. Gosselin,† Michael P. Minitti,† Fedor M. Rudakov,† Theis I. Sølling,‡ and Peter M. Weber*,† J. Phys. Chem. A 2006, 110, 4251-4255 (DMIPA) 3p 3s

8. Proposed Structural Response Tertiary amine changes from an initial pyramidal structure to a planar structure. Relaxation from a local energy minimum to a global minimum: an IVR process.

9. The Process to Become Planar Structure

10. Fit Results Linear peak center shift model Exponential peak center shift model Linear shift Exponential shift (DMIPA)

11. Preliminary Data compond shift amplitude (mev) shift time constant (fs) DEMA74(1)95(2) DMIPA24(2)133(12) DABCO47(1)111(3) CENNA52(2)94(6)

12. Summary The structural response of polyatomic molecules can be complex because more degree of freedom are included. Though complicated, the responses are observable, for instance, using Rydberg Fingerprint Spectroscopy. The initial motion of tertiary amines is on the order of 100fs. The response involves intramolecular vibrational redistribution and structure changes that make the amine planar and rotate the methyl groups.

13. Acknowledgement Prof. Peter Weber Yao Zhang Dr. Sanghamitra Deb Dr. Michael Minitti Dr. Jie Bao Dr. Joseph Geiser Chrishtine Buehler Xiao Liang James Budarz Yan Gao Sonia Vignale Thank You!