001041609 001__ 1041609 001041609 005__ 20250424202216.0 001041609 0247_ $$2doi$$a10.48550/ARXIV.2010.02599 001041609 037__ $$aFZJ-2025-02343 001041609 1001_ $$0P:(DE-HGF)0$$aWallauer, Robert$$b0 001041609 245__ $$aTracing orbital images on ultrafast time scales 001041609 260__ $$barXiv$$c2020 001041609 3367_ $$0PUB:(DE-HGF)25$$2PUB:(DE-HGF)$$aPreprint$$bpreprint$$mpreprint$$s1745495498_9276 001041609 3367_ $$2ORCID$$aWORKING_PAPER 001041609 3367_ $$028$$2EndNote$$aElectronic Article 001041609 3367_ $$2DRIVER$$apreprint 001041609 3367_ $$2BibTeX$$aARTICLE 001041609 3367_ $$2DataCite$$aOutput Types/Working Paper 001041609 520__ $$aFrontier orbitals, i.e., the highest occupied and lowest unoccupied orbitals of a molecule, generally determine molecular properties, such as chemical bonding and reactivities. Consequently, there has been a lot of interest in measuring them, despite the fact that, strictly speaking, they are not quantum-mechanical observables. Yet, with photoemission tomography a powerful technique has recently been introduced by which the electron distribution in orbitals of molecules adsorbed at surfaces can be imaged in momentum space. This has even been used for the identification of reaction intermediates in surface reactions. However, so far it has been impossible to follow an orbital's momentum-space dynamics in time, for example through an excitation process or a chemical reaction. Here, we report a key step in this direction: we combine time-resolved photoemission employing high laser harmonics and a recently developed momentum microscope to establish a tomographic, femtosecond pump-probe experiment of unoccupied molecular orbitals. Specifically, we measure the full momentum-space distribution of transiently excited electrons. Because in molecules this momentum-space distribution is closely linked to orbital shapes, our experiment offers the extraordinary possibility to observe ultrafast electron motion in time and space. This enables us to connect their excited states dynamics to specific real-space excitation pathways. 001041609 536__ $$0G:(DE-HGF)POF4-5213$$a5213 - Quantum Nanoscience (POF4-521)$$cPOF4-521$$fPOF IV$$x0 001041609 588__ $$aDataset connected to DataCite 001041609 650_7 $$2Other$$aChemical Physics (physics.chem-ph) 001041609 650_7 $$2Other$$aMesoscale and Nanoscale Physics (cond-mat.mes-hall) 001041609 650_7 $$2Other$$aOther Condensed Matter (cond-mat.other) 001041609 650_7 $$2Other$$aFOS: Physical sciences 001041609 7001_ $$0P:(DE-Juel1)172607$$aRaths, Miriam$$b1 001041609 7001_ $$0P:(DE-HGF)0$$aStallberg, Klaus$$b2 001041609 7001_ $$0P:(DE-HGF)0$$aMünster, Lasse$$b3 001041609 7001_ $$0P:(DE-HGF)0$$aBrandstetter, Dominik$$b4 001041609 7001_ $$0P:(DE-Juel1)165181$$aYang, Xiaosheng$$b5 001041609 7001_ $$0P:(DE-HGF)0$$aGüdde, Jens$$b6 001041609 7001_ $$0P:(DE-HGF)0$$aPuschnig, Peter$$b7 001041609 7001_ $$0P:(DE-HGF)0$$aSoubatch, Serguei$$b8 001041609 7001_ $$0P:(DE-Juel1)128774$$aKumpf, Christian$$b9$$ufzj 001041609 7001_ $$0P:(DE-HGF)0$$aBocquet, Francois C.$$b10 001041609 7001_ $$0P:(DE-Juel1)128791$$aTautz, Frank Stefan$$b11$$eCorresponding author$$ufzj 001041609 7001_ $$0P:(DE-HGF)0$$aHöfer, Ulrich$$b12 001041609 773__ $$a10.48550/ARXIV.2010.02599 001041609 8564_ $$uhttps://arxiv.org/abs/2010.02599 001041609 909CO $$ooai:juser.fz-juelich.de:1041609$$pVDB 001041609 9101_ $$0I:(DE-588b)5008462-8$$6P:(DE-Juel1)128774$$aForschungszentrum Jülich$$b9$$kFZJ 001041609 9101_ $$0I:(DE-588b)5008462-8$$6P:(DE-Juel1)128791$$aForschungszentrum Jülich$$b11$$kFZJ 001041609 9131_ $$0G:(DE-HGF)POF4-521$$1G:(DE-HGF)POF4-520$$2G:(DE-HGF)POF4-500$$3G:(DE-HGF)POF4$$4G:(DE-HGF)POF$$9G:(DE-HGF)POF4-5213$$aDE-HGF$$bKey Technologies$$lNatural, Artificial and Cognitive Information Processing$$vQuantum Materials$$x0 001041609 9201_ $$0I:(DE-Juel1)PGI-3-20110106$$kPGI-3$$lQuantum Nanoscience$$x0 001041609 980__ $$apreprint 001041609 980__ $$aVDB 001041609 980__ $$aI:(DE-Juel1)PGI-3-20110106 001041609 980__ $$aUNRESTRICTED