Triplet states in isotopically mixed anthracene crystals: High resolution optical spectroscopy

The triplet O,O transitions of guest and host in isotopically mixed anthracene crystals of various compositions (A-h₁₀, ¹³C-monosubstituted A-h₁₀, A-d₁h₉, A-d₂h_g in A-d₁₀ and A-d₁₀ in A-h₁₀) have been investigated using high resolution laser excitation spectroscopy. The guest aggregate spectra have been studied in polarized light as a function of guest concentration up to 15%. The analyses allow us to identify the monomer, dimer and trimer lines. From the dimer splittings the dominant resonance pair interactions are dedu The comparison of different mixed crystal systems with guest levels below and above the host exciton band reveals that quasiresonance and superexchange corrections are of minor importance. The experimental resonance pair interactions are used to calculate the triplet exciton band structure of anthracen and the observed guest polarization behaviour is interpreted quantitatively by the Rashba effect. Finally, the lower Davydov component of the host is s and broadened with increasing guest concentration. The shift is discussed using a theoretical model of Lifshitz.