Hypochromism in two low-energy transitions of B-2 (B-2u) symmetry in the electronic spectrum of the carbazole crystal

TitleHypochromism in two low-energy transitions of B-2 (B-2u) symmetry in the electronic spectrum of the carbazole crystal
Publication TypeJournal Article
Year of Publication2007
AuthorsNakhimovsky L, Fuchs R
Journal TitleMolecular Crystals and Liquid Crystals
Volume473
Pages87-102
Type of ArticleArticle
ISBN Number1542-1406
Accession NumberISI:000251130500008
KeywordsABSORPTION-SPECTRA, ANTHRACENE, carbazole crystal, hypochromism, optical-properties, oscillator strengths, POLY(N-VINYLCARBAZOLE), POLYMERS, POLYNUCLEOTIDES, spectra, transmittance
Abstract

tronic transitions of B-2 (B-2u) symmetry in the carbazole crystal was studied. We have shown that the two lowest-energy transitions of this symmetry exhibit very strong hypochromism-only 22% of the molecular oscillator strength is retained in the crystal spectrum. Polarized transmittance spectra of thin (similar to 0.1 mu) carbazole monocrystals were obtained in the near LW region at normal and oblique incidence of light on the sample. An expression for transmittance as a function of oscillator strengths of the B-2 (B-2u) symmetry electronic transitions in the crystal, and of the angle of incidence of light on the ac face of the crystal, was derived. The experimental oscillator strengths were obtained by fitting the measured transmittance spectra with the derived function. Local field theory was employed to calculate the theoretical values of the oscillator strengths of five individual electronic transitions in the carbazole crystal. The calculations are in agreement with the oscillator strengths sum rule. The theoretically predicted and experimentally obtained values of oscillator strengths of the two lowest B-2 (B-2u) symmetry transitions in the carbazole crystal are in very good agreement.

DOI10.1080/16421400701613441
Alternate JournalMol. Cryst. Liquid Cryst.