English, E.M.L.; (2007) Laser induced ultrafast dynamics in atoms and molecules. Doctoral thesis , University of London.

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Abstract

The dynamics of atoms and molecules in an intense femtosecond laser field are studied experimentally using time-of-flight spectroscopy. 10fe laser pulses have been used to resolve ultrafast vibrational and rotational wave packet dynamics in deuterium, using a pump-probe technique. The revival and subsequent de-phasing of the wave packet is observed with a view to controlling these processes. A new non-Gaussian intensity deconvolution technique is presented, which removes beam diffraction effects and defines the ionisation rate as a constant with respect to ellipticity of laser polarisation. As a consequence of this technique, ultrafast shake-up excitation during tunnel ionisation in atoms has been observed for the first time. The dependence of recollision in an atomic ion on the ellipticity of the laser field has been observed experimentally using laser pulses of 40fs. Through the use of an experimental intensity selective scanning technique, intensity resolved ion yields have been obtained. Following the removal of the laser confocal volume and diffraction effects, the experimental results have been compared with a theoretical model. This quasi-classical model simulates the recollision process in an elliptically polarised laser field.

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