Thermomodulation Study of 0–0 Exciton Absorption Bands in Anthracene

Thermoreflectance spectra in the lowest singlet-singlet transition region of anthracene have been measured at liquid nitrogen temperature. The derivative optical constants are obtained by the Kramers-Kronig analysis of the spectra. The asymmetric broadening of the b -polarized 0-0 exciton absorption band with temperature is suggested. The frequency of the K =0 polariton for the 0-0 bsorpton band has been confirmed to be located at 25484 cm -1 and at 25497 cm -1 in the a - and the b -polarized spectra respectively. The K =0 polariton-exciton splittings for the a - and b -polarization are respectively 77 cm -1 and 378 cm -1 , whose magnitudes are proportional to the oscillator strength of the respective 0-0 absorption band. The b -polarized thermoreflectance spectrum at liquid helium temperature has also been measured and discussed briefly.