Molecular Properties, Spectroscopy, and Photochemistry

We use linear-response coupled-cluster methods, along with other ab initio approaches, to calculate molecular multipole moments and (hyper)polarizabilities and the effect of nuclear motion on these properties. We use first-principles theories to obtain rovibrational, electronic, and rovibronic spectra of molecules and weakly bound species, including van der Waals precursors of photo-induced charge-transfer reactions. We have demonstrated that the lowest excited state of methylcobalamin should be interpreted as metal-to-ligand charge-transfer excitation and that azulene possesses the doubly excited state below the ionization threshold, which can drive multi-photon ionization experiments related to Rydberg fingerprint spectroscopy. We have provided definitive information about structural, electronic, and spectroscopic properties of several organic biradicals and small metal nanoparticles, including, for example, beryllium, magnesium, silver, and gold clusters.