טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShira Weissman
SubjectSite Directed Tunneling in a Multiple Terminal Molecular
Network
DepartmentDepartment of Chemistry
Supervisor Full Professor Peskin Uri
Full Thesis textFull thesis text - English Version


Abstract

A method is introduced for optimizing molecular network parameters so that coherent electron tunneling is possible between a donor and a desired acceptor. The system is   described by a tight-binding Hamiltonian which consists of "sites", associated with

pseudo-potential energies and connected with coupling energies. The molecular network is composed of a donor and several available acceptors sites, connected by some molecular bridges, so that different tunneling pathways are available. Relying on the Feshbach formalism, the Hamiltonian is reduced to an effective donor-acceptor Hamiltonian. In addition, a criterion for maximal possible electron population of the acceptor is derived. Applying an appropriate criterion to the effective Hamiltonian allows an efficient optimization of the full Hamiltonian's parameters such that electron transfer between the donor and the desired acceptor would be maximized.

This non-perturbative approach allows flexible and successful optimization for a wider range of parameters, compared to alternative perturbative methods for reducing the Hamiltonian. Three different model molecular network architectures are examined and comparison is carried out between the different optimization methods for different parameters. The effective Hamiltonian enables calculating an effective donor-acceptor coupling energy parameter, as appears in the Marcus formula for

electron transfer rate in a single donor-acceptor pair.

In addition, when more than a single tunneling pathway connects between the donor and the acceptor, the additive nature of the effective coupling energies regarding each pathway is revealed according to the effective Hamiltonian analysis.