Dr. Gregor Knopp

Gregor Knopp studied  Physics at the  ‘Institut für Angewandte Physik'  TU-Darmstadt in Germany and finished his Diploma in the group of Prof. W. Seelig 1995 in the field of application of nonlinear optical spectroscopy for combustion research.  Later on he completed his PHD (Dr. rer. nat.) at the ‘Institut für Physikalische Chemie ' at the University of Würzburg, Germany  in the group of Prof. W. Kiefer in field of fs-time resolved pump probe and Raman spectrroscopy. In continuation of his interest he joint the group of Prof. Y. Prior at the Weizmann Institute of Science for post doc activities in fs time resolved four wave mixing spectroscopy and quantum control. 2001 Gregor Knopp joined the Paul Scherrer Institute and till 2014 was working in the Molcelur dynamics group within the general energy department (ENE), beeing responsible for time resolved nonlinear spectroscopies and the corresponding laser laserlab facility. From 2014 on he exteneted his interestes towards X-ray - matter interaction and participated in the built up phase of SwissFEL as beamline scientist for the chemical and biological endstation 'Alvra' in the Photon Science Division. Momentarily Gregor Knopp works as research scientist within the 'Laboratory for Synchrotron Radiation and Femtochemistry' (LSF) in the direction of  'advanced experiments' employing the specific modes of the upcomming  'Maloja - Athos  SwissFEL' endstation.

• Exploring the coherent interaction between X-ray photons and matter on the basis of nonlinear X-ray interactions and development of novel types of X-ray spectroscopy.

Nonlinear optical methods have been exploited for molecular dynamics, control and multidimensional correlation spectroscopy and for practical applications, ranging from advanced materials characterization to biomedical imaging to coherent optics used in photonic switching and magnetism. My intention is to extend the momentarily rather limited application field for nonlinear X-ray methods to a similar variety of systems, research fields and methodologies. To date, most applied nonlinear X-ray processes are rather static approaches, detecting characteristic (e.g. spectrally resolved) photon or electron emissions at increased X-ray photon intensities. Time resolved nonlinear X-ray methodologies that comprise spectral-temporal and/or structural-wavevector dependent information in this respect denote a new emerging field of research.  Common X-ray spectroscopy methods provide a high locality and typically involve single-particle transitions between core and valence electronic orbitals. Quantum coherence, which can be revealed and employed by nonlinear spectroscopy, does not usual play a role in linear X-ray techniques. Complex many-body quantum systems involve electron and nuclei motion and/or the evolution of quasi particles like phonons, excitons, magnons or plasmons. Collective relaxation and decoherence gives rise to often complex dynamics. Unambiguous association of the fast (fs) time and short (nm) length scales of the electronic and collective structural rearrangements requires measurements addressing both regimes simultaneously.

1. G. Smolentsev, C. Milne, A. Guda, K. Haldrup, J. Szlachetko, N. Azzaroli, C. Cirelli, G. Knopp, R. Bohinc, S. Menzi, G. Pamfilidis, D. Gashi, M. Beck, A. Mozzanica, D. James, C. Bacellar, G. Mancini, A. Tereshchenko, V. Shapovalov, W. Kwiatek , J. Czapla-Masztafiak, A. Cannizzo, M. Gazzetto, M. Sander, M. Levantino, V. Kabanova, E. Rychagova, S. Ketkov, M. Olaru, J. Beckmann and M. Vogt, Taking a snapshot of the triplet excited state of an OLED organometallic luminophore using X-rays, Nat. Comm., 11, 2131, DOI: 10.1038/s41467-020-15998-z, (2020).
2. R. Bohinc, G. Pamfilidis, J. Rehault, P. Radi, C. Milne, J. Szlachetko, F. Bencivenga, F. Capotondi, R. Cucini, L. Foglia, C. Masciovecchio, R. Mincigrucci, E. Pedersoli, A. Simoncig, A. Cannizzo, H. M. Frey, Z. Ollmann, T. Feurer, A. A. Maznev, K. Nelson, and G. Knopp, Nonlinear XUV-optical transient grating spectroscopy at the Si L2;3 – edge, Appl. Phys. Lett. 114, 181101, DOI:10.1063/1.5085413, (2019).
3. M. Beck, P. Bornhauser, B. Visser, G. Knopp, J. A. van Bokhoven, P. P. Radi, Spectroscopic disentanglement of the quantum states of highly excited Cu₂, Nat. Comm., DOI: 10.1038/s41467-019-11156-2, (2019).
4. Y. Kayser, C. Milne, P. Juranić, L. Sala, J. Czapla-Masztafiak, R. Follath, M. Kavčič, G. Knopp, J. Rehanek, W. Błachucki, M. G. Delcey, M. Lundberg, K. Tyrala, D. Zhu, R. Alonso-Mori, R. Abela, J. Sá, J. Szlachetko, Core-level nonlinear spectroscopy triggered by stochastic X-ray pulses, Nat. Comm., DOI: 10.1038/s41467-019-12717-1, (2019).
5. M. Steglich, G.Knopp and P. Hemberger, How the methyl group position influences the ultrafast deactivation in aromatic radicals, Phys.Chem.Chem.Phys., 21, 581, DOI: 10.1039/c8cp06087h, (2019).
6. C. Svetina, R. Mankowsky, G. Knopp, F. Koch, G. Seniutinas, B. Rösner, A. Kubec, M. Lebugle, I. Mochi, M. Beck, C. Cirelli, J. Krempasky, C. Pradervand, J. Rouxel, G. F. Mancini, S. Zerdane, B. Pedrini, V. Esposito, G. Ingold, U. Wagner, U. Flechsig, R. Follath, M. Chergui, C. Milne, H. T. Lemke, C. David, and P. Beaud, Towards X-ray transient grating spectroscopy, Optics Letters,  Vol. 44,3, 574-577, DOI: 10.1364/OL.44.000574, (2019).
7. A. A. Maznev, F. Bencivenga , A. Cannizzo, F. Capotondi, R. Cucini , R. A. Duncan, T. Feurer, T. D. Frazer , L. Foglia , H.-M. Frey, H. Kapteyn, J. Knobloch, G. Knopp, C. Masciovecchio, R. Mincigrucci, G. Monaco, M. Murnane, I. Nikolov, E. Pedersoli , A. Simoncig, A. Vega-Flick , and K. A. Nelson, Generation of coherent phonons by coherent extreme ultraviolet radiation in a transient grating experiment, Appl. Phys. Lett., 113, 221905; DOI: 10.1063/1.5048023, (2018).
8. M. Tulej, R. Wiesendanger, A. Riedo, G. Knopp, and P. Wurz, Mass spectrometric analysis of the Mg plasma produced by double-pulse femtosecond laser irradiation, J. Anal. At. Spectrom., 33, 1292, DOI: 10.1039/c8ja00036k ,(2018).
9. Yuzhu Liu, Wenyi Yin, Thomas Gerber, Feng Jin and Gregor Knopp, Visualization of the formation of cyclopentylcarbene using time-resolved photoelectron imaging spectroscopy, Laser Phys. Lett., 14 105301, DOI: 10.1088/1612-202X/aa8019, (2017)
10. P. Bornhauser, B. Visser, M. Beck, G. Knopp, J. A. van Bokhoven, R. Marquardt, and P. P. Radi, Experimental and theoretical investigation of the vibrational band structure of the 1⁵P_u - 1⁵P_g  high-spin system of C₂, The Journal of Chemical Physics 146, 114309; DOI: 10.1063/1.4978334, (2017).
11. F. Bencivenga, A. Calvi, F. Capotondi, R. Cucini, R. Mincigrucci, A. Simoncig, M. Manfredda, E. Pedersoli, E. Principi, F. Dallari, R. A. Duncan, M. G. Izzo, G. Knopp, A. A. Maznev, G. Monaco, S. Di Mitri, A. Gessini, L. Giannessi, N. Mahne, I. P. Nikolov, R. Passuello, L Raimondi,M. Zangrando, and C. Masciovecchio, Four-wave-mixing experiments with seeded free electron lasers, Faraday Discussions, doi:10.1039/C6FD00089D, (2016).
12. Yuzhu Liu, Thomas Gerber, Chaochao Qin, Feng Jin, and Gregor Knopp, Visualizing competing intersystem crossing and internal conversion with a complementary measurement, The Journal of Chemical Physics, 144, 084201, DOI: 10.1063/1.4942124, (2016).
13. J. Szlachetko, J.Hoszowska, J.-C. Dousse, M. Nachtegaal, W. Błachucki, Y. Kayser, J. Sà, M. Messerschmidt, S. Boutet, G. J. Williams, C. David, G. Smolentsev, J. A. van Bokhoven, B. D. Patterson, T. J. Penfold, G. Knopp, M. Pajek, R. Abela and C. J. Milne, Establishing nonlinearity thresholds with ultra-intense X-ray pulses, Nature Scientific Reports, DOI: 10.1038/srep33292, (2016).

more Publications

PSI Representative and Member of the FELs of Europe Steering Committee

CLEO-Europe  'Applications of nonlinear optics’
Member of the Scientific Subcommittee (2013-2017) Topic Chair of the Subcommittee (2019)                                   

COST  (European Cooperation in Science and Technology) ’Chemical Imaging by Coherent Raman Microscopy’
 Member of the Management Committee (2012 - 2015)

SNF project: ‘Towards applications of nonlinear X-ray spectroscopy’   Main-Applicant (2016 - 2020)

SNF project: ‘Investigation of ultrafast molecular dynamics of combustion relevant species by time resolved non-linear Raman spectroscopy’. Main-Applicant (2003-2007)

SNF project: ‘Investigations of stable and transient molecules in the gas phase by spectrally and temporally resolved non-linear laser spectroscopy’. Co-Applicant (2010-2012)