Dynamics of optical and X-ray responses of molecules

Abstract: The aim of this licentiatethesis is to investigate by means of theoretical simulationsthe dynamics of light scattering by molecules, with specialemphasis on molecules in gas phase and in solutions.The first part of the thesisconcerns the two-photon absorption (TPA) process in the opticalwavelength region. A new dynamical theory for TPA of moleculesin solutions is developed. The roles of collisions with solventparticles, of pulse duration, of saturation effects and ofpropagation effects on the absorbing capacity of nonlinearmedia are analyzed which can promote a choice of new compoundsfor various applications.The second part addresses thesoft X-ray region of exciting light, namely resonant X-rayRaman scattering (RXS). It is shown that collisional dephasingin solutions changes the physics of X-ray scattering. Anadditional, incoherent contribution to the RXS cross sectioncomes into play, resulting in a doubling of the spectrallines.A theoretical analysis ofdissociative resonant photoelectron spectra of homonucleardiatomic molecules is performed. Special attention is paid tothe electron Doppler effect and to the role of the interferencebetween scattering channels on formation of an atomic-like partof the spectra.The quantum oscillatorybehaviour for the vibrational collapse in the resonant Augerdecay of core excited nitrogen molecule is explored. Aone-phonon model is presented which opens a new possibility todetermine the equilibrium bond distance for a core excitedstates.