PhD defence by Nerijus Rusteika – Niels Bohr Institute - University of Copenhagen

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PhD defence by Nerijus Rusteika

Computational and Experimental Investigation of Ultrafast Photodissociation in Isolated Organic Molecules: Understanding the Effects of Femtosecond Laser Excitation

In this study the ultrafast dissociation of a few organic molecular systems was investigated both experimentally and computationally to clarify some aspects of the photochemical and photophysical reactions in these molecules and to address the effects of their interaction with femtosecond light pulses. The combination of femtosecond mass and photoelectron spectroscopy on gas phase acetone revealed that ultrafast response to the excitation with femtosecond pulses could be attributed to wavepacket relaxation on excited state surface. Similarly, for formaldehyde it was found that internal conversion from the Rydberg states is responsible for ultrafast decay of the ion current. Ultrafast bond breakage was deduced to proceed on the sub-100 fs timescale in the two aliphatic nitrogen containing systems we have studied - N-Chloro-N-ethyl-butylamine and amyl nitrite. The large contribution to the observed dynamics was from the excited state ions efficiently generated by multiphoton ionization. Our research on of amyl nitrite showed that experimental investigation of ultrafast reactivity of molecular ions is possible applying standard techniques of femtochemistry.