2024 

A.R. Ramos, E.W. Fischer,  P. Saalfrank, O. Kühn

Shaping the laser control landscape of a hydrogen transfer reaction by vibrational strong coupling. A direct optimal control approach

J. Chem. Phys. 21 February 2024; 160 (7): 074101. 

Controlling molecular reactivity by shaped laser pulses is a long-standing goal in chemistry. Here, we suggest a direct optimal control approach that combines external pulse optimization with other control parameters arising in the upcoming field of vibro-polaritonic chemistry for enhanced controllability. The direct optimal control approach is characterized by a simultaneous simulation and optimization paradigm, meaning that the equations of motion are discretized and converted into a set of holonomic constraints for a nonlinear optimization problem given by the control functional. Compared with indirect optimal control, this procedure offers great flexibility, such as final time or Hamiltonian parameter optimization. A simultaneous direct optimal control theory will be applied to a model system describing H-atom transfer in a lossy Fabry–Pérot cavity under vibrational strong coupling conditions. Specifically, optimization of the cavity coupling strength and, thus, of the control landscape will be demonstrated.

E.W. Fischer, J.A. Syska, and P. Saalfrank

A Quantum Chemistry Approach to Linear Vibro-Polaritonic Infrared Spectra with Perturbative Electron–Photon Correlation

The Journal of Physical Chemistry Letters 2024 15 (8), 2262-2269

In the vibrational strong coupling (VSC) regime, molecular vibrations and resonant low-frequency cavity modes form light−matter hybrid states, vibrational polaritons, with characteristic infrared (IR) spectroscopic signatures. Here, we introduce a molecular quantum chemistry-based computational scheme for linear IR spectra of vibrational polaritons in polyatomic molecules, which perturbatively accounts for nonresonant electron−photon interactions under VSC. Speci cally, we formulate a cavity Born− Oppenheimer perturbation theory (CBO-PT) linear response approach, which provides an approximate but systematic description of such electron−photon correlation e ects in VSC scenarios while relying on molecular ab initio quantum chemistry methods. We identify relevant electron−photon correlation e ects at the second order of CBO-PT, which manifest as static polarizability-dependent Hessian corrections and an emerging polar- izability-dependent cavity intensity component providing access to transmission spectra commonly measured in vibro-polaritonic chemistry. Illustratively, we address electron−photon correlation e ects perturbatively in IR spectra of CO2 and Fe(CO)5 vibro-polaritonic models in sound agreement with nonperturbative CBO linear response theory.