TY - JOUR

T1 - Generalized quasiclassical ground state for an interacting two-level system

AU - Englman, Robert

AU - Yahalom, Asher

PY - 2004/6

Y1 - 2004/6

N2 - We treat a system (a molecule or a solid) in which electrons are coupled linearly to any number and type of harmonic oscillators and which is further subject to external forces of arbitrary symmetry. With the treatment restricted to the lowest pair of electronic states, approximate "vibronic" (vibration-electronic) ground-state wave functions are constructed having the form of simple, closed expressions. The basis of the method is to regard electronic density operators as classical variables. It extends an earlier "guessed solution," devised for the dynamical Jahn-Teller effect in cubic symmetry, to situations having lower (e.g., dihedral) symmetry or having no symmetry at all. While the proposed solution is expected to be quite close to the exact one, its formal simplicity allows straightforward calculations of several interesting quantities, like energies and vibronic reduction (or Ham) factors. We calculate for dihedral symmetry two different q factors ("qz" and "qx") and a p factor. In simplified situations we obtain p=qz+qx-1. The formalism enables quantitative estimates to be made for the dynamical narrowing of hyperfine lines in the observed electron spin resonance spectrum of the dihedral cyclobutane radical cation.

AB - We treat a system (a molecule or a solid) in which electrons are coupled linearly to any number and type of harmonic oscillators and which is further subject to external forces of arbitrary symmetry. With the treatment restricted to the lowest pair of electronic states, approximate "vibronic" (vibration-electronic) ground-state wave functions are constructed having the form of simple, closed expressions. The basis of the method is to regard electronic density operators as classical variables. It extends an earlier "guessed solution," devised for the dynamical Jahn-Teller effect in cubic symmetry, to situations having lower (e.g., dihedral) symmetry or having no symmetry at all. While the proposed solution is expected to be quite close to the exact one, its formal simplicity allows straightforward calculations of several interesting quantities, like energies and vibronic reduction (or Ham) factors. We calculate for dihedral symmetry two different q factors ("qz" and "qx") and a p factor. In simplified situations we obtain p=qz+qx-1. The formalism enables quantitative estimates to be made for the dynamical narrowing of hyperfine lines in the observed electron spin resonance spectrum of the dihedral cyclobutane radical cation.

UR - http://www.scopus.com/inward/record.url?scp=42749108229&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.69.224302

DO - 10.1103/PhysRevB.69.224302

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AN - SCOPUS:42749108229

SN - 0163-1829

VL - 69

SP - 224302-1-224302-11

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

IS - 22

M1 - 224302

ER -