The exciton transfer Hamiltonian

For a dimer it is easy to show that the symmetric and antisymmetric states 

Electron models with particle-hole symmetry satisfy the condition that 

To prove this, note that under a particle-hole transformation, 

if an eigenstate of the Hamiltonian is also an eigenstate of J, which is automatically the case for a state of definite charge when the number of charges equals the number of orbitals, then 

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For the exciton transfer Hamiltonian defined by eqn (9.16) the general time... 

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