Computational Molecular Spectroscopy of Electronic States

Computational molecular spectroscopy of electronic states encompasses a suite of quantum‐chemical and dynamical methods aimed at predicting and interpreting the interaction of molecules with electromagnetic radiation in electronically excited configurations. Central to this field is the construction of potential energy surfaces that describe the nuclear motion within both ground and excited electronic manifolds. High‐level electronic structure methods such as coupled‐cluster theory and multi‐reference approaches are combined with wavepacket propagation or variational treatments of nuclear motion to yield vibrational and rotational spectra. Recent advances have focused on extending these techniques to larger polyatomic systems, incorporating non‐adiabatic couplings and environment effects, and improving computational efficiency through machine‐learning potentials. Applications span atmospheric and astrochemical processes, photochemical reaction pathways, and the development of novel photonic materials.

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Computational Molecular Spectroscopy of Electronic States publication trend

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Technical terms

Potential energy surface: A multidimensional surface that maps the energy of a molecular system as a function of nuclear coordinates for a given electronic state.

Electronic excited state: A molecular configuration in which one or more electrons occupy higher energy orbitals than in the ground state, often accessed by photon absorption.

Coupled‐cluster singles and doubles with perturbative triples (CCSD(T)): A high‐accuracy quantum‐chemical method that accounts for electron correlation by including single and double excitations exactly and triple excitations approximately.

Equation‐of‐motion coupled‐cluster (EOM-CC): A post-Hartree–Fock approach for computing excited‐state energies and properties by diagonalising a transformed Hamiltonian within the coupled‐cluster framework.

Infrared predissociation spectroscopy: A technique in which weakly bound messenger atoms (e.g., He, Ar) are used to tag ions or neutrals; absorption of infrared photons leads to dissociation of the tag, allowing sensitive measurement of vibrational transitions.

References

1. Ab Initio Potentials for the Ground S 0 and the First Electronically Excited Singlet S 1 States of Benzene–Helium with Application to Tunneling Intermolecular Vibrational States. The Journal of Physical Chemistry A (2024).
2. Structures of the (Imidazole)nH+ ... Ar (n=1,2,3) complexes determined from IR spectroscopy and quantum chemical calculations. Structural Chemistry (2022).