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Title: A Deep-UV Trigger for Ground-State Ring-Opening Dynamics of 1,3-Cyclohexadiene

Abstract

While the ring-opening reaction of 1,3-cyclohexadiene upon excitation to the 1B state has been extensively studied, little is known about the reaction dynamics when exciting higher-lying states. The complexity of the potential energy surfaces found in computational studies suggests that the reaction outcome may depend sensitively on the excitation wavelength and the initially prepared electronic state. We explore the photo-induced kinetics of 1,3-cyclohexadiene upon excitation at 200 nm to the 3p state by ultrafast time-resolved, gas-phase X-ray scattering using the Linac Coherent Light Source (LCLS). Analysis of the experimental scattering data, particularly with respect to the anisotropy, and comparison to ab-initio calculations reveals that the excitation leads dominantly to the 3px and 3py Rydberg electronic states, which relax to the ground state with a time constant of 208 ±11 fs. Unlike in the conventional photochemically induced conrotatory electrocyclic reaction observed at lower excitation energies, at 200 nm the majority of the molecules (76 ± 3%) relax to vibrationally hot cyclohexadiene in the ground electronic state. Furthermore, the photoexcitation activates the reaction on the ground electronic state surface. An equilibrium between the hot cyclohexadiene and 1,3,5-hexatriene is reached by a thermal reaction, giving rates for the forward and backward reaction ofmore » 174 ±13 ps and 355 ±45 ps, respectively. The scattering pattern of the final hexatriene product reveals a thermal distribution of rotamers about the carbon-carbon single bonds. The rapid decay of the initially excited state back into the ring-closed form allows us to observe a ground state chemical reaction using ultrafast X-ray scattering.« less

Authors:
ORCiD logo [1];  [2];  [3];  [2];  [2];  [2];  [2];  [2];  [2];  [4];  [4];  [4];  [1];  [1];  [1];  [1];  [1];  [4]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Brown Univ., Providence, RI (United States)
  3. Brown Univ., Providence, RI (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Univ. of Edinburgh, Edinburgh (United Kingdom)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Energy Information Administration (EIA), Office of Energy Statistics (EI-20); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1529105
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Program Document
Journal Name:
Science Advances
Additional Journal Information:
Journal Name: Science Advances
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS

Citation Formats

Minitti, Michael P., Weber, Peter M., Ruddock, Jennifer M., Yong, Haiwang, Stankus, Brian, Du, Wenpeng, Goff, Nathan, Chang, Yu, Odate, Asami, Carrascosa, Andres Moreno, Bellshaw, Darren, Zotev, Nikola, Liang, Mengning, Carbajo, Sergio, Koglin, Jason, Robinson, Joseph S., Boutet, Sebastian, and Kirrander, Adam. A Deep-UV Trigger for Ground-State Ring-Opening Dynamics of 1,3-Cyclohexadiene. United States: N. p., 2019. Web.
Minitti, Michael P., Weber, Peter M., Ruddock, Jennifer M., Yong, Haiwang, Stankus, Brian, Du, Wenpeng, Goff, Nathan, Chang, Yu, Odate, Asami, Carrascosa, Andres Moreno, Bellshaw, Darren, Zotev, Nikola, Liang, Mengning, Carbajo, Sergio, Koglin, Jason, Robinson, Joseph S., Boutet, Sebastian, & Kirrander, Adam. A Deep-UV Trigger for Ground-State Ring-Opening Dynamics of 1,3-Cyclohexadiene. United States.
Minitti, Michael P., Weber, Peter M., Ruddock, Jennifer M., Yong, Haiwang, Stankus, Brian, Du, Wenpeng, Goff, Nathan, Chang, Yu, Odate, Asami, Carrascosa, Andres Moreno, Bellshaw, Darren, Zotev, Nikola, Liang, Mengning, Carbajo, Sergio, Koglin, Jason, Robinson, Joseph S., Boutet, Sebastian, and Kirrander, Adam. Tue . "A Deep-UV Trigger for Ground-State Ring-Opening Dynamics of 1,3-Cyclohexadiene". United States.
@article{osti_1529105,
title = {A Deep-UV Trigger for Ground-State Ring-Opening Dynamics of 1,3-Cyclohexadiene},
author = {Minitti, Michael P. and Weber, Peter M. and Ruddock, Jennifer M. and Yong, Haiwang and Stankus, Brian and Du, Wenpeng and Goff, Nathan and Chang, Yu and Odate, Asami and Carrascosa, Andres Moreno and Bellshaw, Darren and Zotev, Nikola and Liang, Mengning and Carbajo, Sergio and Koglin, Jason and Robinson, Joseph S. and Boutet, Sebastian and Kirrander, Adam},
abstractNote = {While the ring-opening reaction of 1,3-cyclohexadiene upon excitation to the 1B state has been extensively studied, little is known about the reaction dynamics when exciting higher-lying states. The complexity of the potential energy surfaces found in computational studies suggests that the reaction outcome may depend sensitively on the excitation wavelength and the initially prepared electronic state. We explore the photo-induced kinetics of 1,3-cyclohexadiene upon excitation at 200 nm to the 3p state by ultrafast time-resolved, gas-phase X-ray scattering using the Linac Coherent Light Source (LCLS). Analysis of the experimental scattering data, particularly with respect to the anisotropy, and comparison to ab-initio calculations reveals that the excitation leads dominantly to the 3px and 3py Rydberg electronic states, which relax to the ground state with a time constant of 208 ±11 fs. Unlike in the conventional photochemically induced conrotatory electrocyclic reaction observed at lower excitation energies, at 200 nm the majority of the molecules (76 ± 3%) relax to vibrationally hot cyclohexadiene in the ground electronic state. Furthermore, the photoexcitation activates the reaction on the ground electronic state surface. An equilibrium between the hot cyclohexadiene and 1,3,5-hexatriene is reached by a thermal reaction, giving rates for the forward and backward reaction of 174 ±13 ps and 355 ±45 ps, respectively. The scattering pattern of the final hexatriene product reveals a thermal distribution of rotamers about the carbon-carbon single bonds. The rapid decay of the initially excited state back into the ring-closed form allows us to observe a ground state chemical reaction using ultrafast X-ray scattering.},
doi = {},
journal = {Science Advances},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {7}
}

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