The project aims at developing a coherent control scheme in the perturbative interaction regime by using a phase and amplitude shaped UV pump pulses and at exploiting them as a new spectroscopic tool. Pulse shaping consists in changing the Gaussian amplitude profile of femtosecond pulses by modifying both the phase relationships between the frequencies that make up the pulse and their relative amplitudes.Shaping of ultrafast pulses enabled the active control of physicochemical processes. We propose the implementation of coherent control methods in small systems to steer the outcome of chemical reactions from electronically excited states. This will be realized in gas phase reactions by femtosecond shaped pulses pump-probe spectroscopy involving velocity map imaging for the photoelectron/photoion detection.Gas phase experiments provide the standard for the evaluation of high level ab-initio calculations. A change in the time-resolved signal by the application of a frequency sweep across the pump pulse may elucidate the vibronic couplings governing the molecular dynamics. With theoretical support, we can access to information relating to the critical parameters of these transition barriers.Our goal is to control the outcome of a unimolecular reaction by taking advantage of the phase of the electromagnetic field and the quantum-mechanical phase of the polyatomic molecule. To circumvent the dynamical complexity, we will implement experimentally an adaptive feedback control. As the pulse shaper comprises a very large number of pixels, finding the solution to achieve the desired control is a very time consuming process.We propose a different approach where a phase mask is defined by a mathematical function with a minimum number of control parameters. Then physical effects such as linear and quadratic chirp, pulse duration are maintained, making the problem easier to analyse in order to elucidate the relaxation dynamics and to further propose rational solutions.