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Spin absorption in triplet exciton systems

Citation

Krugler, Joel I. (1965) Spin absorption in triplet exciton systems. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-04112003-110832

Abstract

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A theoretical study of the low-temperature paramagnetic resonance lines of linear-chain organic free-radical crystals characterized by triplet excitons is made by means of a generalized moment method. Techniques which permit the determination of the moments of absorption lines at all temperatures, and to any desired order in interaction parameters, are developed. The necessity for the usual truncation of the hamiltonian is avoided with the aid of the absorption operator expansions of Cheng.

The method is used to calculate the zeroth through fifth moments of the g=2 doublet absorption lines of crystals of Wurster's blue perchlorate. The hamiltonian for the system includes exchange and anisotropic spin interactions, and coupling to a strong external magnetic field. It is shown that exciton creation, annihilation, and transfer processes have negligibly small effect on the absorption. The calculated exciton density, [rho], and the line width, W, have temperature dependence given by [...].

The inclusion of phonon coupling, through distance-dependent exchange integrals, is shown, by means of a canonical linear transformation, to produce an effective exciton-exciton repulsion; this repulsion decays exponentially with distance.

Inclusion of this phonon interaction in the moment calculation leads to exciton density and line width varying like [....] The activation energy, [...]E, can account for the "anomalous" line broadening observed in many triplet systems.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • McConnell, Harden M.
Thesis Committee:
  • Unknown, Unknown
Defense Date:30 September 1964
Record Number:CaltechETD:etd-04112003-110832
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-04112003-110832
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1339
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:11 Apr 2003
Last Modified:26 Dec 2012 02:37

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