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Title: Simplicity Beneath Complexity: Counting Molecular Electrons Reveals Transients and Kinetics of Photodissociation Reactions

Journal Article · · Angewandte Chemie (International Edition)
ORCiD logo [1];  [2];  [3];  [3];  [2];  [4];  [4];  [4];  [4];  [3];  [2]; ORCiD logo [4]; ORCiD logo [3]
  1. Brown Univ., Providence, RI (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Univ. of Edinburgh, Scotland (United Kingdom)
  3. Brown Univ., Providence, RI (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States)
+ Show Author Affiliations

Time-resolved pump–probe gas-phase X-ray scattering signals, extrapolated to zero momentum transfer, give a measure of the number of electrons in a system, an effect that arises from the coherent addition of elastic scattering from the electrons. This allows to identify reactive transients and determine the chemical reaction kinetics without the need for extensive scattering simulations or complicated inversion of scattering data. We investigate the photodissociation reaction of trimethylamine and identify two reaction paths upon excitation to the 3p state at 200 nm: a fast dissociation path out of the 3p state to the dimethyl amine radical (16.6±1.2 %) and a slower dissociation via internal conversion to the 3s state (83.4±1.2 %). The time constants for the two reactions are 640±130 fs and 74±6 ps, respectively. Additionally, it is found that the transient dimethyl amine radical has a N-C bond length of 1.45±0.02 Å and a C-N-C bond angle of 118°±4°.

Research Organization:
Brown Univ., Providence, RI (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
Royal Society of Edinburgh; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Contributing Organization:
SLAC National Laboratory
Grant/Contract Number:
AC02-76SF00515; SC0017995
OSTI ID:
1532505
Journal Information:
Angewandte Chemie (International Edition), Journal Name: Angewandte Chemie (International Edition) Journal Issue: 19 Vol. 58; ISSN 1433-7851
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (5)

A deep UV trigger for ground-state ring-opening dynamics of 1,3-cyclohexadiene journal September 2019
Ultrafast X-ray scattering reveals vibrational coherence following Rydberg excitation journal July 2019
Theory of ultrafast x-ray scattering by molecules in the gas phase journal November 2019
Scattering off molecules far from equilibrium journal August 2019
A deep UV trigger for ground-state ring-opening dynamics of 1,3-cyclohexadiene journal September 2019

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
free-electron lasers
free-electron lasers · gas-phase kinetics · photodissociation dynamics · ultrafast X-ray scattering
gas-phase kinetics
photodissociation dynamics
ultrafast X-ray scattering