Abstract
The ultraviolet-induced photochemistry of five-membered heterocyclic rings often involves ring opening as a prominent excited-state relaxation pathway. The identification of this particular photoinduced mechanism, however, presents a challenge for many experimental methods. We show that femtosecond X-ray transient absorption spectroscopy at the carbon K-edge (similar to 284 eV) provides core-to-valence spectral fingerprints that enable the unambiguous identification of ring-opened isomers of organic heterocycles. The unique differences in the electronic structure between a carbon atom bonded to the oxygen in the ring versus a carbon atom set free of the oxygen in the ring-opened product are readily apparent in the X-ray spectra. Ultrafast ring opening via C-O bond fission occurs within similar to 350 fs in 266-nm photoexcited furfural, as evidenced by fingerprint core (carbon 1s) electronic transitions into a nonbonding orbital of the open-chain carbene intermediate at 283.3 eV. The lack of recovery of the 1s pi* ground-state depletion in furfural at 286.4 eV indicates that internal conversion to the ground state is a minor channel. These experimental results, augmented by recent advances in the generation of isolated attosecond pulses at the carbon K-edge, will pave the way for probing ring-opened conical intersection dynamics in the future.
| Item Type: | Journal article |
|---|---|
| Faculties: | Chemistry and Pharmacy > Department of Chemistry |
| Subjects: | 500 Science > 540 Chemistry |
| ISSN: | 0002-7863 |
| Language: | English |
| Item ID: | 67564 |
| Date Deposited: | 19. Jul 2019, 12:22 |
| Last Modified: | 04. Nov 2020, 13:49 |
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