Influence of Exciton Phonon Interaction on Metallic Reflection from Molecular Crystals

Optical Reflection Spectroscopy of Organic Solids

“…This phenomenon, which we here call "quasimetallic" reflection, was first investigated spectroscopically by Anex & Simpson (14), who found that the stop-bands of some polymethine dye crystals were 1 to 2 e V in width. In subsequent work many more examples of quasi-metallic reflection were discovered (15)(16)(17). Unfor tunately, in the early work, lack of detailed crystal structure information hampered penetrating theoretical interpretation of the spectra.…”

“…There have been many theoretical treatments of the exciton-phonon coupling problem-much of it relevant to molecular crystals (16,(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). However, there have been no calculations based on any of the theories advanced so far that satisfactorily account for the apparent vibrational structure within the stop-band region of the reflection spectrum.…”

Background Polarization in the Dipole Theory of Molecular Exciton States

“…G L ·aL (13) where T=T(k), ax=ax(w) , and (14) with X = L or U. In the absence of any driving field Ex the polarization PL of the lower states satisfies (15) The allowed exciton frequencies are found by setting the determinant of the coefficient of P L , in Eq. (15), to zero.…”

“…15 The influence of high-lying states on the energy and intensity of lower exciton levels is considered using a theory which is exact in the dipole and single-particle approximations.…”

The crystal and molecular structure of the polymethine dye 1,3-bis(dimethylamino)trimethinium perchlorate: a comparison of optical and X-ray crystal structure determination

“…The crystals of certain polymethine dyes are of interest because of their most unusual optical properties (Anex & Simpson, 1960;Fanconi, Gerhold & Simpson, 1969). For incident light polarized in one direction and frequency near an intense transition of the isolated molecule, these crystals have reflection properties akin to metals, whereas for light polarized in a different direction the crystals are essentially transparent.…”