ChemRxiv
These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
1/1
2 files

X-Ray Transient Absorption Reveals the 1Au (Nπ*) State of Pyrazine in Electronic Relaxation

preprint
submitted on 04.02.2021, 19:53 and posted on 05.02.2021, 12:53 by Valeriu Scutelnic, Shota Tsuru, Mátyás Imre Pápai, Zheyue Yang, Michael Epshtein, Tian Xue, Eric Haugen, Yuki Kobayashi, Anna Krylov, Klaus Braagaard Møller, Sonia Coriani, Stephen Leone
Electronic relaxation in organic chromophores often proceeds via states not directly accessible by photoexcitation. We report on the photoinduced dynamics of pyrazine that involves such states, excited by a 267 nm laser and probed with X-ray transient absorption spectroscopy in a table-top setup. In addition to the previously characterized 1B2u (ππ*) (S2) and 1B3u (nπ*) (S1) states, the participation of the optically dark 1Au (nπ*) state is assigned by a combination of experimental X-ray core-to-valence spectroscopy, electronic structure calculations, nonadiabatic dynamics simulations, and X-ray spectral computation. Despite 1Au (nπ*) and 1B3u (nπ*) states having similar energies at relaxed geometry, their X-ray absorption spectra differ largely in transition energy and oscillator strength. The 1Au (nπ*) state is populated about 200 femtoseconds after electronic excitation and plays a key role in the relaxation of pyrazine to the ground state.

Funding

V.S., M.E., T.X., E.H., Z.Y. and S.R.L. - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (Contract No. DEAC02- 05CH11231), the gas phase chemical physics program through the Chemical Sciences Division of Lawrence Berkeley National Laboratory.

V.S. - Swiss National Science Foundation (P2ELP2_184414).

S.T. - European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 713683 (COFUNDfellowsDTU).

S.C., M.P. and K.B.M. - Danish Council for Independent Research (now Independent Research Fund Denmark), Grant Nos. 7014-00258B (S.C.), 4002-00272 (M.P., K.B.M.), 014-00258B (M.P., K.B.M.), and 8021-00347B(M.P., K.B.M.).

A.I.K. - U.S. National Science Foundation (No. CHE-1856342).

History

Email Address of Submitting Author

scutelnic@berkeley.edu

Institution

Department of Chemistry, University of California, Berkeley, CA 94720, USA

Country

United States

ORCID For Submitting Author

0000-0001-9209-1242

Declaration of Conflict of Interest

The authors declare the following competing financial interest: A.I.K. is the president and a part owner of Q-Chem, Inc.

Exports