Title: Modelling molecules in electric and magnetic fields
Próf. Kenneth Ruud Centre for Theoretical and Computational Chemistry Department of Chemistry University of Tromsø, N-9037 Tromsø, Norway
Abstract:
The study of molecules in electric and magnetic fields is gaining increas- ing theoretical interest, due to the possibilities offered by nonlinear optics in designing functional materials with superior properties for use for instance in three dimensional optical data storage, microfabrication, optical power lim- iting, upconverted lasing, fluorescence imaging, and photo-dynamic therapy. Added control comes also from involving vibrational excitations as well as the possibilities of exploring the magnetic component of the electromagnetic light, leading to a range of chiroptical spectroscopies and birefringences. A challenge for the theoretical study of such nonlinear phenomena in- volving electronic and vibrational degrees of freedoms for molecules exposed to electric and magnetic fields is the high order of the molecular properties and the fact that the basis set depends explicitly on the positions of the nuclei and also on the external magnetic field if Gauge-Including Atomic Orbitals (GIAOs) are used. In the lecture, I will outline the main features of a new approach we have developed for the calculation of higher-order frequency-dependent molec- ular response properties using perturbation-dependent basis sets for self- consistent field states and wave functions. A novelty of the approach is the fact that the theory is formulated fully in the atomic orbital basis, allowing us to take advantage of recent advances in linearly scaling computational methodology. Being formulated in the atomic orbital basis, the formalism is also easily extended to two- and four-component relativistic SCF methods. The main part of the lecture will focus on showing different applications of the methodology, demonstrating both how theory may aid experimen- tal analysis, as well as give examples where agreement between theory and experiment is still lacking. Particular attention will be given to nonlinear vibrational spectroscopy and different Raman scattering processes in par- ticular, but examples of nonlinear optical properties as well a birefringences will be given.
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