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Relaxation Dynamics of Hydrated Thymine, Thymidine, and Thymidine Monophosphate Probed by Liquid Jet Time-Resolved Photoelectron Spectroscopy

preprint
submitted on 29.08.2019, 23:35 and posted on 30.08.2019, 15:56 by Blake Erickson, Zachary Heim, Elisa Pieri, Erica Liu, Todd J. Martínez, Daniel Neumark

The relaxation dynamics of thymine and its derivatives thymidine and thymidine monophosphate were studied using time-resolved photoelectron spectroscopy applied to a water microjet. Two absorption bands were studied, the first is a bright ππ* state which was populated using tunable-ultraviolet light in the range of 4.74 – 5.17 eV and probed using a 6.20 eV probe pulse. By reversing the order of these pulses, a band containing multiple ππ* states was populated by the 6.20 eV pulse and the lower energy pulse served as the probe. The lower lying ππ* state was found to decay in ~400 fs in both thymine and thymidine independent of pump photon energy while thymidine monophosphate decays varied from 670-840 fs with some pump energy dependence.

The application of a computational QM/MM scheme at the XMS-CASPT2//CASSCF/AMBER level of theory suggests that conformational differences existing between thymidine and thymidine monophosphate in solution accounts for this difference. The higher lying ππ* band was found to decay in ~600 fs in all three cases, but was only able to be characterized when using the 5.17 eV probe pulse. Notably, no long-lived signal from an np* state could be identified in either experiment on any of the three molecules.

Funding

National Science Foundation CHE- 1663832

Air Force Office of Scientific Research as part of a Multidisciplinary University Initiative Award No. 24086151-01

University of California at Berkeley Center for Solvation Studies, CALSOLV

University of California at Berkeley Department of Chemistry Graduate Student Fellowship Support

AMOS program within the Chemical Sciences, Geosciences and Biosciences Division of the Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy

History

Email Address of Submitting Author

blakeerickson@berkeley.edu

Institution

University of California Berkeley

Country

United State of America

ORCID For Submitting Author

0000-0002-0763-890X

Declaration of Conflict of Interest

no conflict of interest

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