MOLECULAR-DYNAMICS FROM ELECTRONIC-SPECTRA - A SIMPLE APPROACH FOR DONOR-ACCEPTOR COMPLEXES OF IODINE

A simple semiempirical model for the B <-- X optical transition, which is strongly manifested in the visible absorption spectra of the free and complexed iodine molecule, is presented. The blue shift and broade ning of the band seen on donor-acceptor complexation are shown to be t he result of an essential increase in the overall reorganization energ y of the molecular systems involved. Contributions to the resulting re organization energy arise from the molecular dynamics associated with iodine-iodine bond elongation and donor-diiodine bond compression, lea ving the overall distance between the two partially charged terminal a toms virtually constant. Numerical values for these contributions aris ing from two considered degrees of freedom are estimated.