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Title: Ultrafast Intersystem Crossing in Acetylacetone via Femtosecond X-ray Transient Absorption at the Carbon K-Edge

Abstract

Here, molecular triplet states constitute a crucial gateway in the photochemical reactions of organic molecules by serving as a reservoir for the excess electronic energy. Here, we report the remarkable sensitivity of soft X-ray transient absorption spectroscopy for following the intricate electronic structure changes accompanying the non-adiabatic transition of an excited molecule from the singlet to the triplet manifold. Core-level X-ray spectroscopy at the carbon-1s K-edge (284 eV) is applied to identify the role of the triplet state (T 1, 3ππ*) in the ultraviolet-induced photochemistry of pentane-2,4-dione (acetylacetone, AcAc). The excited-state dynamics initiated at 266 nm ( 1ππ*, S 2) is investigated with element- and site-specificity using broadband soft X-ray pulses produced by high harmonic generation, in combination with time-dependent density functional theory calculations of the X-ray spectra for the excited electronic singlet and triplet states. The evolution of the core-to-valence resonances at the carbon K-edge establishes an ultrafast population of the T 1 state ( 3ππ*) in AcAc via intersystem crossing on a 1.5 ± 0.2 ps time scale.

Authors:
 [1];  [2];  [3];  [4]; ORCiD logo [3]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Bristol, Bristol (United Kingdom)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); MIT Lincoln Lab., Lexington, MA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1463399
Grant/Contract Number:  
AC02-76SF00515; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 46; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Bhattacherjee, Aditi, Pemmaraju, Chaitanya Das, Schnorr, Kirsten, Attar, Andrew R., and Leone, Stephen R. Ultrafast Intersystem Crossing in Acetylacetone via Femtosecond X-ray Transient Absorption at the Carbon K-Edge. United States: N. p., 2017. Web. doi:10.1021/jacs.7b07532.
Bhattacherjee, Aditi, Pemmaraju, Chaitanya Das, Schnorr, Kirsten, Attar, Andrew R., & Leone, Stephen R. Ultrafast Intersystem Crossing in Acetylacetone via Femtosecond X-ray Transient Absorption at the Carbon K-Edge. United States. doi:10.1021/jacs.7b07532.
Bhattacherjee, Aditi, Pemmaraju, Chaitanya Das, Schnorr, Kirsten, Attar, Andrew R., and Leone, Stephen R. Mon . "Ultrafast Intersystem Crossing in Acetylacetone via Femtosecond X-ray Transient Absorption at the Carbon K-Edge". United States. doi:10.1021/jacs.7b07532. https://www.osti.gov/servlets/purl/1463399.
@article{osti_1463399,
title = {Ultrafast Intersystem Crossing in Acetylacetone via Femtosecond X-ray Transient Absorption at the Carbon K-Edge},
author = {Bhattacherjee, Aditi and Pemmaraju, Chaitanya Das and Schnorr, Kirsten and Attar, Andrew R. and Leone, Stephen R.},
abstractNote = {Here, molecular triplet states constitute a crucial gateway in the photochemical reactions of organic molecules by serving as a reservoir for the excess electronic energy. Here, we report the remarkable sensitivity of soft X-ray transient absorption spectroscopy for following the intricate electronic structure changes accompanying the non-adiabatic transition of an excited molecule from the singlet to the triplet manifold. Core-level X-ray spectroscopy at the carbon-1s K-edge (284 eV) is applied to identify the role of the triplet state (T1, 3ππ*) in the ultraviolet-induced photochemistry of pentane-2,4-dione (acetylacetone, AcAc). The excited-state dynamics initiated at 266 nm (1ππ*, S2) is investigated with element- and site-specificity using broadband soft X-ray pulses produced by high harmonic generation, in combination with time-dependent density functional theory calculations of the X-ray spectra for the excited electronic singlet and triplet states. The evolution of the core-to-valence resonances at the carbon K-edge establishes an ultrafast population of the T1 state (3ππ*) in AcAc via intersystem crossing on a 1.5 ± 0.2 ps time scale.},
doi = {10.1021/jacs.7b07532},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 46,
volume = 139,
place = {United States},
year = {2017},
month = {10}
}

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