• rotational spectroscopy
• QED
• multipolar Hamiltonian
• enantiomer
• chiral cavity

It is known that strong coupling to light can be used to manipulate properties of matter. This regime can be experimentally achieved by inserting a molecular system into an optical cavity. In this thesis, we introduce quantum electrodynamic theory inside a chiral cavity (i.e. hosting a precise handedness of circularly polarised light) to study the effects on enantiomers. The important issue of discrimination between two enantiomers is here addressed through a theoretical study of the interaction Hamiltonian. Starting from minimal coupling formalism, for convenience the Hamiltonian has been expanded in multipoles and truncated at the quadrupole level. Quantum electrodynamical Hartree-Fock (QED-HF) was developed for energy calculations inside cavities. Rotational spectroscopy was chosen for the investigation of energy differences of molecules placed in left (LCP) and right (RCP) circularly polarised cavities. The theory of rotations for asymmetric tops has been used for the calculation of transition energies of the tested systems (peroxide, L-Serine, D-Proline, D-Thalidomide). We show that the distinction of enantiomers is possible through the analysis of rotational spectra.