Research

Methods development for high-dimensional quantum dynamics

Our main tool for simulating and studying the quantum dynamics of molecular systems is the MCTDH method and its multilayer-MCTDH generalization. Our research group is very active in further developing MCTDH both in theory as well as software implementation, together with a comprehensive set of tools for analysis and visualization. We distribute the source code on request to interested researchers.

MCTDH wavepacket dynamics
  1. O. Vendrell, H.-D. Meyer, J. Chem. Phys. 134, 044135 (2011). DOI
  2. L. Cao, S. Krönke, O. Vendrell, P. Schmelcher, J. Chem. Phys. 139, 134103 (2013). DOI
  3. M. Schröder, J. Chem. Phys. 152, 024108 (2020). DOI
  4. S. Sasmal, O. Vendrell J. Chem. Phys. 153, 154110 (2020). DOI
  5. D. Mendive-Tapia, H.-D. Meyer, O. Vendrell, J. Chem. Theory Comput. 19, 1144 (2023). DOI
  6. S. Sasmal, M. Schröder, O. Vendrell J. Chem. Phys. 160, 064109 (2024) DOI

Strong coupling and molecular polaritonics

Strong coupling between confined field modes in optical cavities and molecular degrees of freedom opens the way to the formation of hybrid light-matter states, named polaritons, that showcase novel properties. We tackle these coupled systems via full quantum dynamical simulations to gain insight into phenomena like transport, energy transfer and rate modifications, shining light onto the fundamental principles governing polaritonic dynamics.

Molecular polaritonics
  1. O. Vendrell, Phys. Rev. Lett. 121, 253001 (2018). DOI
  2. I. S. Ulusoy, O. Vendrell, J. Chem. Phys. 153, 044108 (2020). DOI
  3. J. Sun, O. Vendrell, J. Phys. Chem. Lett. 13, 4441 (2022). DOI
  4. F. Mellini, O. Vendrell, J. Phys. Chem. Lett. 16, 6155 (2025). DOI
  5. N. Krupp, O. Vendrell, Nat. Commun. 16, 5431 (2025). DOI

Dynamics of highly flexible molecules and clusters

Protonated water clusters are key to understand charge transfer in liquid water and are the building blocks of what is known as the Grotthus mechanism. Interestingly, protonated water clusters of different sizes exhibit very different gas phase IR spectra caused by the strong coupling of the proton motion to the solvation shells. New developments of surface refitting in our group made it possible to study these systems in full-dimensional quantum simulations.

Protonated water clusters
  1. O. Vendrell, F. Gatti, H.-D. Meyer, Angew. Chem. Int. Ed. 46, 6918 (2007). DOI
  2. O. Vendrell, F. Gatti, H.-D. Meyer, J. Chem. Phys. 127, 184303 (2007). DOI
  3. M. Schröder, F. Gatti, D. Lauvergnat, H.-D. Meyer, O. Vendrell, Nat. Commun. 13, 6170 (2022). DOI

Non-adiabatic phenomena

Quantum systems in which the Born-Oppenheimer approximation breaks down and which are hence vibronically strongly coupled are common in the photochemistry of poly-atomic molecules. We extensively work on the development of computational tools to treat the non-adiabatic couplings of such systems in full dimensionality, which allows us to analyze the dynamics through conical intersections and avoided crossings.

Non-adiabatic dynamics
  1. C. Arnold, O. Vendrell, R. Welsch, R. Santra, Phys. Rev. Lett. 120, 123001 (2018). DOI
  2. I. S. Ulusoy, J. A. Gomez, O. Vendrell, J. Phys. Chem. A 123, 8832 (2019). DOI
  3. K. R. Nandipati, O. Vendrell, Phys. Rev. A 107, L061101 (2023). DOI
  4. K. R. Nandipati, O. Vendrell, J. Chem. Phys. 153, 224308 (2020). DOI

Time-resolved spectroscopy

Our focus lies on the simulation of time-resolved observables which are experimentally accessible. This includes time-resolved X-ray photoelectron spectra and time-resolved X-ray absorption spectra among others. These spectra encode information about the dynamics of the molecule and allow to track electron and nuclear dynamics in detail.

Time-resolved spectroscopy
  1. A. Freibert, D. Mendive-Tapia, N. Huse, O. Vendrell, J. Phys. B: At. Mol. Opt. Phys. 54, 244003 (2021). DOI
  2. A. Freibert, D. Mendive-Tapia, N. Huse, O. Vendrell, J. Chem. Theory Comput. 20, 2167 (2024). DOI
  3. E. Rodríguez-Cuenca, A. Picón, S. Oberli, A. I. Kuleff, O. Vendrell, Phys. Rev. Lett. 132, 263202 (2024). DOI

Ultrafast dynamics of highly excited molecules

Attosecond spectroscopy gives us insights into electron motion on its natural timescale. Using high-level electronic structure ab-initio calculations together with the full quantum treatment of the nuclei we are studying ultrafast processes in core excited molecules.

Intermolecular Coulombic decay

Intermolecular Coulombic decay (ICD) is an environment driven relaxation process that can occur in weakly bound systems, including liquid water. In ICD, excess energy of an initially ionized atom or molecule is efficiently transferred to a neighboring atom or molecule, ionizing also the latter. We develop accurate models to simulate the full quantum dynamics of the system, including building of non-Hermitian Hamiltonians, methods for the calculation of decay rates and diabatization procedures, used together with the MCTDH approach.

Bibliography of ICD and related phenomena