Photophysics and photochemistry of molecules /
We present a model suitable for performing realistic simulations of nonadiabatic processes in complex molecules and materials. The model was first used within an orthogonal tight-binding scheme to simulate the photoexcitation of coherent phonons. It was then generalized to incorporate nonorthogonal...
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
2001.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728909061&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | We present a model suitable for performing realistic simulations of nonadiabatic processes in complex molecules and materials. The model was first used within an orthogonal tight-binding scheme to simulate the photoexcitation of coherent phonons. It was then generalized to incorporate nonorthogonal basis sets. With further extension to a density-functional based tight-binding scheme, simulations were performed on the fullerene C₆₀ to study various photoexcitation phenomena over a range of intensities. Photofragmentation of C₆₀ proceeds with the emission of carbon dimers. The photofragmentation of small linear chains, on the other hand, leads to the emission of trimers. The collision of C₆₀ with a projectile atom was observed to produce cage fragmentation, with the emission of two carbon dimers, followed by subsequent reformation of a new fullerene C₅₆ with a 7-membered ring and a compensating extra pentagon. Simulations with organic molecules include the photoinduced 2+2 cycloaddition reaction in which cyclobutane is produced from two ethylene molecules. The selective photodissociation reaction of cyclobutane revealed the formation of the tetramethylene diradical reaction intermediate. The photoisomerization of butadiene was observed to proceed from both trans-to-cis and cis-to-trans. Lastly, it was demonstrated that both electronic excitations and vibrations can be coherently controlled in benzene. The above results are compared to the available experimental data, and the agreement is remarkably good. However, the simulations provide detailed microscopic information about ultrafast phenomena which is inaccessible in the experiments. |
|---|---|
| Item Description: | Vita. "Major Subject: Physics". |
| Physical Description: | xxv, 168 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 159-167). |