Molecular radicals are efficient electroluminescent emitters due to the spin multiplicity of their electronic states. The excited states often exhibit a complex composition with multiple significant electronic configurations, which are essential for their optoelectronic properties but difficult to probe directly. Here we use light-scanning tunneling microscopy to investigate such an excited state by visualizing the response of a single radical molecule to a laser excitation. We observe characteristic atomic-scale spatial photocurrent patterns that can be tuned by applied bias voltage. We interpret these patterns as resulting from decay of an excited doublet state through sequential electron transfers with the tip and the substrate. The relative contributions of two dominating electronic configurations involved in this excited state are tuned by the applied voltage. This approach thus allows for disentangling the components of multiconfigurational excited states in single molecules.

Faculty of Mathematics and Physics Charles University Ke Karlovu 3 CZ12116 Praha 2 Czech Republic

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo náměstí 542 2 CZ16000 Praha 6 Czech Republic

Institute of Physics Czech Academy of Sciences Cukrovarnická 10 112 CZ16200 Praha 6 Czech Republic

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Ai, X. et al. Efficient radical-based light-emitting diodes with doublet emission. PubMed

Tonnelé, C. & Casanova, D. Rationalization and tuning of doublet emission in organic radicals.

Heil, A. & Marian, C. M. DFT/MRCI-R2018 study of the photophysics of the zinc(ii) tripyrrindione radical: non-Kasha emission?. PubMed

Doležal, J. et al. Real space visualization of entangled excitonic states in charged molecular assemblies. PubMed

de Campos Ferreira, R. C. et al. Resonant tip-enhanced raman spectroscopy of a single-molecule kondo system. PubMed PMC

Gouterman, M. Spectra of porphyrins.

Parusel, A. B. J. & Grimme, S. DFT/MRCI calculations on the excited states of porphyrin, hydroporphyrins, tetrazaporphyrins and metalloporphyrins.

Schulten, K., Ohmine, I. & Karplus, M. Correlation effects in the spectra of polyenes.

Bettinger, H. F., Tönshoff, C., Doerr, M. & Sanchez-Garcia, E. Electronically excited states of higher acenes up to nonacene: a density functional theory/multireference configuration interaction study. PubMed

Jiang, S., Neuman, T., Boeglin, A., Scheurer, F. & Schull, G. Topologically localized excitons in single graphene nanoribbons. PubMed

Abdurahman, A. et al. Understanding the luminescent nature of organic radicals for efficient doublet emitters and pure-red light-emitting diodes. PubMed

Xu, Z. et al. Revealing generation, migration, and dissociation of electron-hole pairs and current emergence in an organic photovoltaic cell. PubMed PMC

Kristiansson, M. K. et al. Experimental and theoretical studies of excited states in Ir

Regeta, K., Bannwarth, C., Grimme, S. & Allan, M. Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method. PubMed

Helmich-Paris, B. CASSCF linear response calculations for large open-shell molecules. PubMed

Lischka, H. et al. Multireference approaches for excited states of molecules. PubMed

Lüftner, D. et al. Imaging the wave functions of adsorbed molecules. PubMed PMC

Imai-Imada, M. et al. Orbital-resolved visualization of single-molecule photocurrent channels. PubMed

Zhu, R. et al. Revealing single-molecule photocurrent generation mechanisms under on- and off-resonance excitation. PubMed

Garg, M., Martin-Jimenez, A., Luo, Y. & Kern, K. Ultrafast photon-induced tunneling microscopy. PubMed PMC

Garg, M. et al. Real-space subfemtosecond imaging of quantum electronic coherences in molecules.

Yao, J., Park, Y., Shi, W., Chen, S. & Ho, W. Origin of photoinduced DC current and two-level population dynamics in a single molecule. PubMed PMC

Chen, C., Chu, P., Bobisch, C. A., Mills, D. L. & Ho, W. Viewing the interior of a single molecule: vibronically resolved photon imaging at submolecular resolution. PubMed

Yang, B. et al. Sub-nanometre resolution in single-molecule photoluminescence imaging.

Jaculbia, R. B. et al. Single-molecule resonance Raman effect in a plasmonic nanocavity. PubMed

Sellies, L., Eckrich, J., Gross, L., Donarini, A. & Repp, J. Controlled single-electron transfer enables time-resolved excited-state spectroscopy of individual molecules. PubMed PMC

Cochrane, K. A., Schiffrin, A., Roussy, T. S., Capsoni, M. & Burke, S. A. Pronounced polarization-induced energy level shifts at boundaries of organic semiconductor nanostructures. PubMed PMC

Kimura, K. et al. Selective triplet exciton formation in a single molecule. PubMed

Scheuerer, P., Patera, L. L. & Repp, J. Manipulating and probing the distribution of excess electrons in an electrically isolated self-assembled molecular structure. PubMed

Doležal, J., Sagwal, A., de Campos Ferreira, R. C. & Švec, M. Single-molecule time-resolved spectroscopy in a tunable stm nanocavity. PubMed PMC

Rosławska, A. et al. Submolecular-scale control of phototautomerization. PubMed

Friedrich, N. et al. Fluorescence from a single-molecule probe directly attached to a plasmonic STM tip. PubMed PMC

Hernangómez-Pérez, D. et al. Reorganization energy and polaronic effects of pentacene on NaCl films.

Lin, C. et al. Continuous-wave multiphoton-induced electron transfer in tunnel junctions driven by intense plasmonic fields.

Ortiz, J. V. Dyson-orbital concepts for description of electrons in molecules. PubMed

Pomogaev, V., Lee, S., Shaik, S., Filatov, M. & Choi, C. H. Exploring dyson’s orbitals and their electron binding energies for conceptualizing excited states from response methodology. PubMed

Truhlar, D. G., Hiberty, P. C., Shaik, S., Gordon, M. S. & Danovich, D. Orbitals and the interpretation of photoelectron spectroscopy and (e,2e) ionization experiments. PubMed

Neuman, T., Esteban, R., Casanova, D., García-Vidal, F. J. & Aizpurua, J. Coupling of molecular emitters and plasmonic cavities beyond the point-dipole approximation. PubMed

Rosławska, A. et al. Mapping lamb, stark, and purcell effects at a chromophore-picocavity junction with hyper-resolved fluorescence microscopy.

Kaiser, K. et al. Gating single-molecule fluorescence with electrons. PubMed

Koch, J., von Oppen, F. & Andreev, A. V. Theory of the Franck-Condon blockade regime.

Jiang, S. et al. Many-body description of STM-induced fluorescence of charged molecules. PubMed

Vasilev, K. et al. Exploring the role of excited states’ degeneracy on vibronic coupling with atomic-scale optics. PubMed PMC

Becke, A. D. Density-functional thermochemistry. III. The role of exact exchange.

Frisch, M. J. et al.

Grimme, S., Ehrlich, S. & Goerigk, L. Effect of the damping function in dispersion corrected density functional theory. PubMed

Lu, T. A comprehensive electron wavefunction analysis toolbox for chemists. PubMed

Tancogne-Dejean, N. et al. Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems. PubMed

Perdew, J. P. & Zunger, A. Self-interaction correction to density-functional approximations for many-electron systems.

Slater, J. C. A Simplification of the hartree-fock method.

Dirac, P. A. M. Note on exchange phenomena in the thomas atom.

Imai-Imada, M. et al. Energy-level alignment of a single molecule on ultrathin insulating film.