Static and Dynamic Theoretical Studies on Vibronic Model Based Potential Energy Surface(s): Locating Transition Structures and Fundamental Investigations in Time-resolved Spectroscopy

Vibronic Model;TRPES;Transition State Search;Empirical Valence Bond;Potential Energy Surface;Femtosecond Spectroscopy;Quantum Dynamics

Goel, Prateekaffiliation1:Faculty of Science ; advisor:Nooijen, Marcel ; Nooijen, Marcel ;

University of Waterloo

关键词: Potential Energy Surface;    Empirical Valence Bond;    Quantum Dynamics;    Femtosecond Spectroscopy;    TRPES;    Vibronic Model;    Doctoral Thesis;    Transition State Search;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/12528/1/Goel_Prateek.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Construction and exploration of Potential Energy Surfaces (PES) is central to the study of manyinteresting chemical phenomena, such as computing the rate of a chemical reaction or elucidatingstructure of a complex molecule. Locating a transition state structure on a PES is an importantproblem as it provides a qualitative as well as quantitative understanding of reaction rates andmechanisms. A powerful example of this is the celebrated Transition State Theory (TST). Finding a transition state structure is a nontrivial and challenging task for reasons such as the lackof a good starting geometry or the PES having complicated topological features. The problemof characterizing critical points on a PES can be classified as ;;static;; approaches to understandchemical structure and reactivity. When the interest lies in understanding dynamical processes,one needs to solve the time-dependent Schr¨odinger equation (TDSE). Although solving TDSEcontains more ;;Physics;;, however, it also becomes harder to interpret the complex information itcarries and to provide simple answers.In this work, an attempt has been made on both static and dynamic fronts to address problemsof fundamental importance, while proposing new and unconventional solutions to these problems.In first part of the thesis, a strategy to locate transition states using the vibronic model basedPES has been proposed, implemented, and tested on a primary test set of unimolecular reactions.The approximate representation of the ground state PES using vibronic model serves as a powerful tool for transition state search by providing cheap means to compute the gradient and hessian on the PES, which are essential (or desirable, in particular the hessian) quantities for geometry optimization techniques. On the dynamic front, in second part of the thesis a new schemefor time-dependent photoelectron spectroscopy has been proposed, denoted as pump-repump-cwphotoelectron spectroscopy (PRP-CW-PES), which provides vibronically resolved fingerprintsfor a series of time-delay between pump-and repump pulses. In principle, the proposed schemecan be used to distinguish between closely related molecular structures, and can also serve as anew tool to study wave packet interferometry (WPI). The basic theory of the proposed scheme isoutlined with application to simple model systems. Attention of the experimental community iscalled for realization of the experiment in the laboratory.