<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers"^^ . "The phenomena of photo-induced chemical reactions can exhibit kinetics as short as a few femtoseconds. The development of femtosecond UV pulses enables the investigation of such ultrafast phenomena in more experimentally challenging, UV absorbing systems. This thesis describes, chronologically, development of a UV transient absorption (TA) system and its application to various coumarin-based molecular systems. The experimental section details the TA system comprising of three major components: two tunable UV excitation sources giving a total excitation range of 250-350 nm, supercontinuum generation enabling 240-700 nm probe range, and multichannel detection with greater than 5 ×10-5 OD sensitivity. The potential of the TA setup was tested on the study of ultrafast relaxation in 7-hydroxy coumarin. Following successful tests, the photo-induced cleavage reaction of coumarin dimer was studied in order to understand the ultrafast dynamics. The experiments utilized 280 nm excitation and broadband (300-650 nm) probing. The results revealed fast cleavage occurring through short-lived nonradiative (<200 fs) singlet states. Two branched kinetic models were developed to describe the monomer formation and dimer relaxation dynamics, identify intermediate states, and determine the quantum yields. The anti-hh displayed the highest cleavage efficiency of ~20 %. Finally, variation in the quantum yields between isomers was rationalized using a sequential bond cleavage mechanism over a concerted, “pericyclic-style” ring cleavage."^^ . "2017" . . . . . . . "Man"^^ . "Jiang"^^ . "Man Jiang"^^ . . . . . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers (PDF)"^^ . . . "Man-Jiang-Dissertation-2016.pdf"^^ . . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Femtosecond UV Transient Absorption Study of Coumarin Dimers (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #22677 \n\nFemtosecond UV Transient Absorption Study of Coumarin Dimers\n\n" . "text/html" . . . "500 Naturwissenschaften und Mathematik"@de . "500 Natural sciences and mathematics"@en . . . "530 Physik"@de . "530 Physics"@en . .