TY  - JOUR
A1  - Battistoni, A.
A1  - Dürr, H. A.
A1  - Gühr, Markus
A1  - Wolf, Thomas J. A.
T1  - A tilted pulse-front setup for femtosecond transient grating spectroscopy in highly non-collinear geometries
JF  - Journal of optics
N2  - We demonstrate a tilted pulse-front transient grating (TG) technique that allows to optimally utilize time resolution as well as TG line density while probing under grazing incidence as typically done in extreme ultraviolet (EUV) or soft x-ray (SXR) experiments. Our optical setup adapts the pulse front tilt of the two pulses that create the TG to the grazing incident pulse. We demonstrate the technique using all 800 nm femtosecond laser pulses for TG generation on a vanadium dioxide film. We probe that grating via diffraction of a third 800 nm pulse. The time resolution of 90 fs is an improvement by a factor of 30 compared to our previous experiments on the same system. The scheme paves the way for EUV and SXR probing of optically induced TGs on any material.
KW  - transient grating spectroscopy
KW  - ultrafast spectroscopy
KW  - pulse front matching
Y1  - 2018
U6  - https://doi.org/10.1088/2040-8986/aad60a
SN  - 2040-8978
SN  - 2040-8986
VL  - 20
IS  - 9
PB  - IOP Publ. Ltd.
CY  - Bristol
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  - Xiong, Hui
A1  - Fang, Li
A1  - Osipov, Timur
A1  - Kling, Nora G.
A1  - Wolf, Thomas J. A.
A1  - Sistrunk, Emily
A1  - Obaid, Razib
A1  - Gühr, Markus
A1  - Berrah, Nora
T1  - Fragmentation of endohedral fullerene Ho3N@C-80 in an intense femtosecond near-infrared laser field
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - The fragmentation of gas phase endohedral fullerene, Ho3N@C-80, was investigated using femtosecond near-infrared laser pulses with an ion velocity map imaging spectrometer. We observed that Ho+ abundance associated with carbon cage opening dominates at an intensity of 1.1 x 10(14) W/cm(2). As the intensity increases, the Ho+ yield associated with multifragmentation of the carbon cage exceeds the prominence of Ho+ associated with the gentler carbon cage opening. Moreover, the power law dependence of Ho+ on laser intensity indicates that the transition of the most likely fragmentation mechanisms occurs around 2.0 x 10(14) W/cm(2).
Y1  - 2018
U6  - https://doi.org/10.1103/PhysRevA.97.023419
SN  - 2469-9926
SN  - 2469-9934
VL  - 97
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Myhre, Rolf H.
A1  - Wolf, Thomas J. A.
A1  - Cheng, Lan
A1  - Nandi, Saikat
A1  - Coriani, Sonia
A1  - Gühr, Markus
A1  - Koch, Henrik
T1  - A theoretical and experimental benchmark study of core-excited states in nitrogen
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. The computational results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure. Published by AIP Publishing.
Y1  - 2018
U6  - https://doi.org/10.1063/1.5011148
SN  - 0021-9606
SN  - 1089-7690
VL  - 148
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Holzmeier, Fabian
A1  - Wolf, Thomas J. A.
A1  - Gienger, Christian
A1  - Wagner, Isabella
A1  - Bozek, J.
A1  - Nandi, S.
A1  - Nicolas, C.
A1  - Fischer, Ingo
A1  - Gühr, Markus
A1  - Fink, Reinhold F.
T1  - Normal and resonant Auger spectroscopy of isocyanic acid, HNCO
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - In this paper, we investigate HNCO by resonant and nonresonant Auger electron spectroscopy at the K-edges of carbon, nitrogen, and oxygen, employing soft X-ray synchrotron radiation. In comparison with the isosteric but linear CO2 molecule, spectra of the bent HNCO molecule are similar but more complex due to its reduced symmetry, wherein the degeneracy of the π-orbitals is lifted. Resonant Auger electron spectra are presented at different photon energies over the first core-excited 1s → 10a′ resonance. All Auger electron spectra are assigned based on ab initio configuration interaction computations combined with the one-center approximation for Auger intensities and moment theory to consider vibrational motion. The calculated spectra were scaled by a newly introduced energy scaling factor, and generally, good agreement is found between experiment and theory for normal as well as resonant Auger electron spectra. A comparison of resonant Auger spectra with nonresonant Auger structures shows a slight broadening as well as a shift of the former spectra between −8 and −9 eV due to the spectating electron. Since HNCO is a small molecule and contains the four most abundant atoms of organic molecules, the reported Auger electron decay spectra will provide a benchmark for further theoretical approaches in the computation of core electron spectra.
Y1  - 2018
U6  - https://doi.org/10.1063/1.5030621
SN  - 0021-9606
SN  - 1089-7690
VL  - 149
IS  - 3
PB  - American Institute of Physics
CY  - Melville
ER  -