Perturbations on quantum dynamical systems are of great relevance both in chemical physics and physical chemistry. The present study has answered a few such questions and raised many more. The ionization of halide anions explored through model can be calculated on solvated halide anions to extract accurate ion-water potentials. Studies on modelling thermal effects on photo-dissociation dynamics and dynamics of tunnelling indicate that part of the effects is accounted for by our choice and may be compared with experimental results. The proton as well as electron transfer processes can be explored in the connection of tunnelling phenomena. The quantum hysteresis is interesting as it arises out of the competition between two time-scales, the time scale of driving and relaxation. The time-lag between the two processes is important in determining the fate of energy redistribution in the systems after it is pumped in. Another important question concerning the Landau-Zener transition rates...