TY  - JOUR
A1  - Berrah, N.
A1  - Sánchez-González, Álvaro
A1  - Jurek, Zoltan
A1  - Obaid, Razib
A1  - Xiong, H.
A1  - Squibb, R. J.
A1  - Osipov, T.
A1  - Lutman, A.
A1  - Fang, L.
A1  - Barillot, T.
A1  - Bozek, J. D.
A1  - Cryan, J.
A1  - Wolf, T. J. A.
A1  - Rolles, Daniel
A1  - Coffee, R.
A1  - Schnorr, Kirsten
A1  - Augustin, S.
A1  - Fukuzawa, Hironobu
A1  - Motomura, K.
A1  - Niebuhr, Nina Isabelle
A1  - Frasinski, L. J.
A1  - Feifel, Raimund
A1  - Schulz, Claus-Peter
A1  - Toyota, Kenji
A1  - Son, Sang-Kil
A1  - Ueda, K.
A1  - Pfeifer, T.
A1  - Marangos, J. P.
A1  - Santra, Robin
T1  - Femtosecond-resolved observation of the fragmentation of buckminsterfullerene following X-ray multiphoton ionization
JF  - Nature physics
N2  - X-ray free-electron lasers have, over the past decade, opened up the possibility of understanding the ultrafast response of matter to intense X-ray pulses. In earlier research on atoms and small molecules, new aspects of this response were uncovered, such as rapid sequences of inner-shell photoionization and Auger ionization. Here, we studied a larger molecule, buckminsterfullerene (C-60), exposed to 640 eV X-rays, and examined the role of chemical effects, such as chemical bonds and charge transfer, on the fragmentation following multiple ionization of the molecule. To provide time resolution, we performed femtosecond-resolved X-ray pump/X-ray probe measurements, which were accompanied by advanced simulations. The simulations and experiment reveal that despite substantial ionization induced by the ultrashort (20 fs) X-ray pump pulse, the fragmentation of C-60 is considerably delayed. This work uncovers the persistence of the molecular structure of C-60, which hinders fragmentation over a timescale of hundreds of femtoseconds. Furthermore, we demonstrate that a substantial fraction of the ejected fragments are neutral carbon atoms. These findings provide insights into X-ray free-electron laser-induced radiation damage in large molecules, including biomolecules.
Y1  - 2019
U6  - https://doi.org/10.1038/s41567-019-0665-7
SN  - 1745-2473
SN  - 1745-2481
VL  - 15
IS  - 12
SP  - 1279
EP  - 1301
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wolf, Thomas J. A.
A1  - Sanchez, David M.
A1  - Yang, J.
A1  - Parrish, R. M.
A1  - Nunes, J. P. F.
A1  - Centurion, M.
A1  - Coffee, R.
A1  - Cryan, J. P.
A1  - Gühr, Markus
A1  - Hegazy, Kareem
A1  - Kirrander, Adam
A1  - Li, R. K.
A1  - Ruddock, J.
A1  - Shen, Xiaozhe
A1  - Vecchione, T.
A1  - Weathersby, S. P.
A1  - Weber, Peter M.
A1  - Wilkin, K.
A1  - Yong, Haiwang
A1  - Zheng, Q.
A1  - Wang, X. J.
A1  - Minitti, Michael P.
A1  - Martinez, Todd J.
T1  - The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction
JF  - Nature chemistry
N2  - The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subangstrom length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the subpicosecond timescale.
KW  - Organic chemistry
KW  - Photochemistry
KW  - Physical chemistry
KW  - Theoretical chemistry
Y1  - 2019
U6  - https://doi.org/10.1038/s41557-019-0252-7
SN  - 1755-4330
SN  - 1755-4349
VL  - 11
IS  - 6
SP  - 504
EP  - 509
PB  - Nature Publ. Group
CY  - London
ER  -