Gessner Group
At the Forefront of Ultrafast X-ray Science
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Our group explores ultrafast dynamics in molecules, clusters, and interfacial systems by a variety of state-of-the-art time-resolved XUV and X-ray spectroscopy as well as X-ray and electron imaging techniques. We strive to provide the most detailed understanding possible of the atomic-scale couplings, correlations and dynamics that govern collective behavior in atomic clusters, chemical transformations in molecules, and solar light harvesting processes in molecular and condensed phase systems. Our experiments reach sensitivities on the level of single electrons, atoms, and molecules, and cover temporal scales ranging from femtoseconds to microseconds. We employ laboratory based femtosecond XUV transient absorption, XUV photoelectron and ion imaging, X-ray free electron laser (X-FEL) and synchrotron based time-resolved X-ray spectroscopy and coherent diffractive imaging techniques, as well as ultrafast electron diffraction (UED) to study ultrafast reaction dynamics in molecules, energy and charge transfer dynamics at interfaces relevant for solar light harvesting applications, as well as the fundamental dynamics underlying the coupled and correlated motion in ground state, excited state, and highly ionized atomic clusters.
Working across boundaries of a variety of scientific disciplines, our group is a lively mixture of chemists and physicists with diverse backgrounds and origins, joined by their excitement for science and the knowledge that our team's diversity is key to our success. Together with our international collaborators, we push the boundaries of knowledge in an environment fostered by mutual respect, personal growth, and a shared passion for scientific excellence.
More details of our research projects can be found here, our list of publications can be found here.
We frequently have openings for internships, graduate projects, and postdoctoral research opportunities. Feel free to contact us.
Recent News
Happy New Year 2025! The UNESCO International Year of Quantum Science and Technology.
Watching a Molecular Reaction in Real Time
Enjoying some sweets during group meeting to celebrate Lars' JACS article on studying ultrafast UV-induced dynamics in bromoform using femtosecond ultrafast electron diffraction (UED). LBNL's landing page looked really good that day thanks to Melody's artwork for the occasion and our sponsors liked it, too. The experiment had been performed at the LCLS UED facility at SLAC National Accelerator Laboratory with incredible support by the facility staff. Thanks so much!
Successful Picosecond Time-Resolved Ambient-Pressure X-ray Photoelectron Spectroscopy campaign at the ALS
Smiling faces after our team successfully completed the first picosecond time-resolved ambient pressure XPS experiment on photoinduced charge-transfer dynamics in a nanoplasmonic solar light harvesting system at the Advanced Light Source. Many thanks to the ALS staff for all their support!
Anisotropic Nanoplasma Dynamics work published in Physical Review Letters
A big thank you to all our collaborators from around the globe for making this possible, and congratulations to Camila on achieving this exceptional feat in the world of ultrafast X-ray imaging.
UXSS 2022 at SLAC National Accelerator Laboratory
UXSS 2022 at SLAC National Accelerator Laboratory
Zach and Sahan joined the Ultrafast X-ray Summer School 2022, a 4 day workshop that introduces students and postdocs to the opportunities and ultrafast science available at X-ray Free Electron Lasers (FELs), such as LCLS.
October 2024: Lars' study of ultrafast UV-induced dynamics in bromoform using femtosecond ultrafast electron diffraction appears in JACS. Congrats Lars!
February 15, 2023: Zach passes his PhD qualifying exam. Congratulations Zach!
February 6, 2023: Elham re-joins our group, following her ASPIRES internship in 2022. Welcome back Elham!
November 2022: Performed the first picosecond time-resolved ambient pressure x-ray photoelectron spectroscopy experiment at the Advanced Light Source. The results will provide deeper insight into critical parameters determining interfacial charge transfer dynamics in nanoplasmonic solar light harvesting systems.
August 2022: Catherine graduates with her work on Dynamics in Helium Nanodroplets Induced via Multiphoton Absorption in the XUV and X-ray Regimes. Congratulations Catherine!
August 12, 2022: Camila's work on Anisotropic Surface Broadening and Core Depletion during the Evolution of a Strong-Field Induced Nanoplasma is published in Physical Review Letters!
June 2022: Sahan and Zach attend the UXSS 2022 Summer School at SLAC National Accelerator Laboratory.
June 6th, 2022: Welcome to our new intern student Elham! She will be with us for the summer as part of the LBNL ASPIRES program.
June 2022: Lars attends DAMOP 2022 in Orlando FL and presents the latest results of his ultrafast electron diffraction study of UV-induced dissociation of bromoform.
May 11th, 2022: Matthew's baby is born, welcome to the group Wesley!
April 27th, 2022: Johannes passes his PhD defense and graduates with his work on Probing Photoinduced Charge and Energy Transfer on the Nanoscale with Time-Resolved X-ray Spectroscopy Techniques; congratulations Johannes!
February 2022: Sahan joins the group as a Postdoc to study interfacial energy and charge transfer by time-resolved X-ray photoemission spectroscopy. Welcome Sahan!
January 2022: Zach joins the group as a Graduate Student, working on charge transfer dynamics in nanoplasmonic light harvesting systems. Welcome Zach!
December 9, 2021: Stefans' and Johannes' paper on Nanoscale Confinement of Photo-Injected Electrons at Hybrid Interfaces is published as a Cover Article in The Journal of Physical Review Letters.
September 6, 2021: Catherine's paper on Charging and ion ejection dynamics of large helium nanodroplets exposed to intense femtosecond soft X-ray pulses is published in The European Physical Journal Special Topics.
Selected Recent Publications
Selected Recent Publications
Lars Hoffmann, Benjamin W. Toulson, Jie Yang, Catherine A. Saladrigas, Alfred Zong, Sri Bhavya Muvva, Joao Pedro Figueira Nunes, Alexander Reid, Andrew R. Attar, Duan Luo, Fuhao Ji, Ming-Fu Lin, Qingyuan Fan, Stephen Weathersby, Xiaozhe Shen, Xijie Wang, Thomas J. A. Wolf, Daniel M. Neumark, Stephen R. Leone, Michael W. Zuerch, Martin Centurion and Oliver Gessner, “UV-induced reaction pathways in bromoform probed with ultrafast electron diffraction”, J. Am. Chem. Soc. 146, 28070 (2024), DOI: 10.1021/jacs.4c07165, Department of Energy Science Highlight.
Benjamin W. Toulson, Diptarka Hait, Davide Faccialà, Daniel M. Neumark, Stephen R. Leone, Martin Head-Gordon, and Oliver Gessner, “Probing C–I Bond Fission in the UV Photochemistry of 2-Iodothiophene with Core-to-Valence Transient Absorption Spectroscopy”, J. Chem. Phys. 159, 034304 (2023), DOI: 10.1063/5.0151629.
C. Bacellar, A. S. Chatterley, F. Lackner, C. D. Pemmaraju, R. M. P. Tanyag, D. Verma, C. Bernando, S. O’Connell, M. Bucher, K. R. Ferguson, T. Gorkhover, R. Coffee, G. Coslovich, D. Ray, T. Osipov, D. M. Neumark, C. Bostedt, A. F. Vilesov, and O. Gessner, “Anisotropic surface broadening and core depletion during the evolution of a strong-field induced nanoplasma”, Phys. Rev. Lett. 129, 073201 (2022), DOI: 10.1103/PhysRevLett.129.073201.
Alexandra J. Feinberg, Deepak Verma, Sean M.O. O’Connell, Swetha Erukala, Rico M.P. Tanyag, Weiwu Pang, Catherine A. Saladrigas, Benjamin W. Toulson, Mario Borgwardt, Niranjan Shivaram, Ming-Fu Lin, Andre Al Haddad, Wolfgang Jäger, Christoph Bostedt, Peter Walter, Oliver Gessner and Andrey F. Vilesov, “Aggregation of solutes in bosonic versus fermionic quantum fluids”, Sci. Adv. 7, eabk2247 (2021), DOI: 10.1126/sciadv.abk2247.
Stefan Neppl, Johannes Mahl, Friedrich Roth, Giuseppe Mercurio, Guosong Zeng, Francesca M. Toma, Nils Huse, Peter Feulner, and Oliver Gessner, “Nanoscale confinement of photoinjected electrons at hybrid interfaces”, J. Phys. Chem. Lett. 12, 11951 (2021), DOI: 10.1021/acs.jpclett.1c02648, Cover Article, Department of Energy Science Highlight.
Davide Faccialà, Benjamin W. Toulson, and Oliver Gessner, “Removal of correlated background in high-order harmonic transient absorption spectra with principal component regression”, Opt. Express 29, 35135 (2021), DOI: 10.1364/OE.435008.
Felix Brausse, Mario Borgwardt, Johannes Mahl, Matthew Fraund, Friedrich Roth, Monika Blum, Wolfgang Eberhardt, and Oliver Gessner, “Real-time Interfacial Electron Dynamics Revealed through Temporal Correlations in X-ray Photoelectron Spectroscopy”, Struct. Dyn. 8, 044301 (2021), DOI: 10.1063/4.0000099.
Friedrich Roth, Mario Borgwardt, Lukas Wenthaus, Johannes Mahl, Steffen Palutke, Günter Brenner, Serguei Molodtsov, Wilfried Wurth, Oliver Gessner, and Wolfgang Eberhardt, “Direct observation of charge separation in an organic light harvesting system by femtosecond time-resolved XPS”, Nat. Commun. 12, 1196 (2021), DOI: 10.1038/s41467- 021-21454-3, Science Highlight in DESY Annual Photon Science Report 2021.
Mario Borgwardt, Johannes Mahl, Friedrich Roth, Lukas Wenthaus, Felix Brauße, Monika Blum, Klaus Schwarzburg, Guiji Liu, Francesca M. Toma, and Oliver Gessner, “Photoinduced charge carrier dynamics and electron injection efficiencies in Au nanoparticlesensitized TiO2 determined with picosecond time-resolved X-ray photoelectron spectroscopy”, J. Phys. Chem. Lett. 11, 5476 (2020), DOI: 10.1021/acs.jpclett.0c00825, Department of Energy Science Highlight.
Benjamin W. Toulson, Mario Borgwardt, Han Wang, Florian Lackner, Adam S. Chatterley, C. D. Pemmaraju, Daniel M. Neumark, Stephen R. Leone, David Prendergast and Oliver Gessner, “Probing Ultrafast C–Br Bond Fission in the UV Photochemistry of Bromoform with Core-to-Valence Transient Absorption Spectroscopy”, Struct. Dyn. 6, 054304 (2019), DOI: 10.1063/1.5113798.
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