Prediction of optically-induced vibrations in large biomolecules

Non-covalent van Der Waals (vdW) forces are due to coupled dipole oscillations, and play a key role in determining structural properties of large molecules, actively influencing their vibrational spectra. Upon optical excitation, charge oscillation modes can be activated, causing a dramatic change of vdW interactions and introducing non-local stress in the molecular structure. Vibrational modes are thus expected to be activated by energy transfer from optically-excited charge-fluctuation modes. A quantum-mechanical model for the interaction between charge oscillations and vibrational modes is proposed here, based on the many body dispersion (MBD) model, where the problem is reduced to a set of coupled quantum harmonic oscillators. The aim is to study the vibrational modes activation, analyzing the transition between relevant quantum states within a perturbative framework, and to specifically analyze molecular systems such as photo-receptors and host-guest complexes.