Optical Properties of Anthracene Single Crystals

Abstract

Reflection spectra of anthracene are analysed by Kramers-Kronig method in the wavelength region from 192 to 600 mμ. The oscillator strength of the first electronic transition A_1g→B_2u is obtained with Lorentz field correction. The oscillator strength for individual vibronic band at room temperature is in excellent agreement with that obtained in the solution spectrum. The total oscillator strength f_a+f_b is 0.100 and 0.107 at room and at liquid nitrogen temperatures respectively. The quantity of the ratio of the oscillator strength as well as the absolute value of the oscillator strength is discussed in connection with the ratio of absorption intensities. Result suggests that the first vibronic band involves a contribution which arises from a thermally induced transition.
Lorentz field in the anthracene crystal shows large anisotropy with respect to the direction of electric field applied. The oscillator strength obtained by simplified method is compared with that reported by several investigators.