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  - 
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, T. J. A.
A1  - Myhre, R. H.
A1  - Cryan, J. P.
A1  - Coriani, S.
A1  - Squibb, R. J.
A1  - Battistoni, A.
A1  - Berrah, Nora
A1  - Bostedt, Christoph
A1  - Bucksbaum, Philip H.
A1  - Coslovich, G.
A1  - Feifel, R.
A1  - Gaffney, K. J.
A1  - Grilj, J.
A1  - Martinez, T. J.
A1  - Miyabe, S.
A1  - Moeller, S. P.
A1  - Mucke, M.
A1  - Natan, A.
A1  - Obaid, R.
A1  - Osipov, T.
A1  - Plekan, O.
A1  - Wang, S.
A1  - Koch, H.
A1  - Guehr, Markus
T1  - Probing ultrafast pi pi*/n pi* internal conversion in organic chromophores via K-edge resonant absorption
JF  - Nature Communications
Y1  - 2017
U6  - https://doi.org/10.1038/s41467-017-00069-7
SN  - 2041-1723
VL  - 8
SP  - 14317
EP  - 14322
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Yang, Jie
A1  - Zhu, Xiaolei
A1  - Wolf, Thomas J. A.
A1  - Li, Zheng
A1  - Nunes, João Pedro Figueira
A1  - Coffee, Ryan
A1  - Cryan, James P.
A1  - Gühr, Markus
A1  - Hegazy, Kareem
A1  - Heinz, Tony F.
A1  - Jobe, Keith
A1  - Li, Renkai
A1  - Shen, Xiaozhe
A1  - Veccione, Theodore
A1  - Weathersby, Stephen
A1  - Wilkin, Kyle J.
A1  - Yoneda, Charles
A1  - Zheng, Qiang
A1  - Martinez, Todd J.
A1  - Centurion, Martin
A1  - Wang, Xijie
T1  - Imaging CF3I conical intersection and photodissociation dynamics with ultrafast electron diffraction
JF  - Science
N2  - Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways of many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these intersections directly. Here, we present the simultaneous experimental characterization of one-photon and two-photon excitation channels in isolated CF3I molecules using ultrafast gas-phase electron diffraction. In the two-photon channel, we have mapped out the real-space trajectories of a coherent nuclear wave packet, which bifurcates onto two potential energy surfaces when passing through a conical intersection. In the one-photon channel, we have resolved excitation of both the umbrella and the breathing vibrational modes in the CF3 fragment in multiple nuclear dimensions. These findings benchmark and validate ab initio nonadiabatic dynamics calculations.
Y1  - 2018
U6  - https://doi.org/10.1126/science.aat0049
SN  - 0036-8075
SN  - 1095-9203
VL  - 361
IS  - 6397
SP  - 64
EP  - 67
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wolf, Thomas J. A.
A1  - Holzmeier, Fabian
A1  - Wagner, Isabella
A1  - Berrah, Nora
A1  - Bostedt, Christoph
A1  - Bozek, John
A1  - Bucksbaum, Phil
A1  - Coffee, Ryan
A1  - Cryan, James
A1  - Farrell, Joe
A1  - Feifel, Raimund
A1  - Martinez, Todd J.
A1  - McFarland, Brian
A1  - Mucke, Melanie
A1  - Nandi, Saikat
A1  - Tarantelli, Francesco
A1  - Fischer, Ingo
A1  - Gühr, Markus
T1  - Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra
JF  - Applied sciences
N2  - Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymines neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.
KW  - ultrafast dynamics
KW  - Auger electron spectroscopy
KW  - photofragmentation
KW  - photochemistry
Y1  - 2017
U6  - https://doi.org/10.3390/app7070681
SN  - 2076-3417
VL  - 7
IS  - 7
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Wolf, Thomas J. A.
A1  - Holzmeier, Fabian
A1  - Wagner, Isabella
A1  - Berrah, Nora
A1  - Bostedt, Christoph
A1  - Bozek, John
A1  - Bucksbaum, Philip H.
A1  - Coffee, Ryan
A1  - Cryan, James
A1  - Farrell, Joe
A1  - Feifel, Raimund
A1  - Martinez, Todd J.
A1  - McFarland, Brian
A1  - Mucke, Melanie
A1  - Nandi, Saikat
A1  - Tarantelli, Francesco
A1  - Fischer, Ingo
A1  - Gühr, Markus
T1  - Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra
JF  - Applied Sciences
N2  - Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.
KW  - ultrafast dynamics
KW  - Auger electron spectroscopy
KW  - photofragmentation
KW  - photochemistry
Y1  - 2017
U6  - https://doi.org/10.3390/app7070681
SN  - 2076-3417
VL  - 7
IS  - 7
PB  - MDPI
CY  - Basel
ER  - 
TY  - GEN
A1  - Wolf, Thomas J. A.
A1  - Holzmeier, Fabian
A1  - Wagner, Isabella
A1  - Berrah, Nora
A1  - Bostedt, Christoph
A1  - Bozek, John
A1  - Bucksbaum, Philip H.
A1  - Coffee, Ryan
A1  - Cryan, James
A1  - Farrell, Joe
A1  - Feifel, Raimund
A1  - Martinez, Todd J.
A1  - McFarland, Brian
A1  - Mucke, Melanie
A1  - Nandi, Saikat
A1  - Tarantelli, Francesco
A1  - Fischer, Ingo
A1  - Gühr, Markus
T1  - Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra
N2  - Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 386 
KW  - Auger electron spectroscopy
KW  - photochemistry
KW  - photofragmentation
KW  - ultrafast dynamics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402692
ER  -