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  - Wilkin, Kyle J.
A1  - Parrish, Robert M.
A1  - Yang, Jie
A1  - Wolf, Thomas J. A.
A1  - Nunes, J. Pedro F.
A1  - Gühr, Markus
A1  - Li, Renkai
A1  - Shen, Xiaozhe
A1  - Zheng, Qiang
A1  - Wang, Xijie
A1  - Martinez, Todd J.
A1  - Centurion, Martin
T1  - Diffractive imaging of dissociation and ground-state dynamics in a complex molecule
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - We have investigated the structural dynamics in photoexcited 1,2-diiodotetrafluoroethane molecules (C2F4I2) in the gas phase experimentally using ultrafast electron diffraction and theoretically using FOMO-CASCI excited-state dynamics simulations. The molecules are excited by an ultraviolet femtosecond laser pulse to a state characterized by a transition from the iodine 5p perpendicular to orbital to a mixed 5p parallel to sigma hole and CF2 center dot antibonding orbital, which results in the cleavage of one of the carbon-iodine bonds. We have observed, with sub-Angstrom resolution, the motion of the nuclear wave packet of the dissociating iodine atom followed by coherent vibrations in the electronic ground state of the C2F4I radical. The radical reaches a stable classical (nonbridged) structure in less than 200 fs.
Y1  - 2019
U6  - https://doi.org/10.1103/PhysRevA.100.023402
SN  - 2469-9926
SN  - 2469-9934
VL  - 100
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Wang, Feipeng
A1  - Zhang, Zheng
A1  - Yan, Yuyang
A1  - Shen, Zijia
A1  - Wang, Qiang
A1  - Gerhard, Reimund
T1  - Surface reconstruction on electro-spun PVA/PVP nanofibers by water evaporation
JF  - Nanomaterials
N2  - Tailoring the secondary surface morphology of electro-spun nanofibers has been highly desired, as such delicate structures equip nanofibers with distinct functions. Here, we report a simple strategy to directly reconstruct the surface of polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) nanofibers by water evaporation. The roughness and diameter of the nanofibers depend on the temperature during vacuum drying. Surface changes of the nanofibers from smooth to rough were observed at 55 degrees C, with a significant drop in nanofiber diameter. We attribute the formation of the secondary surface morphology to the intermolecular forces in the water vapor, including capillary and the compression forces, on the basis of the results from the Fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy. The strategy is universally effective for various electro-spun polymer nanofibers, thus opening up avenues toward more detailed and sophisticated structure design and implementation for nanofibers.
KW  - surface reconstruction
KW  - intermolecular force
KW  - surface-roughened
KW  - nanofiber
Y1  - 2022
U6  - https://doi.org/10.3390/nano12050797
SN  - 2079-4991
VL  - 12
IS  - 5
PB  - MDPI
CY  - Basel
ER  -