The Optical Properties of Anthracene Single Crystals

A single crystal of anthracene with (010) orientation is grown from melt by Bridgman method. A large and transparent crystal with a mirror-like cleavage plane can be grown with an insertion of seed. From the remarkable double refraction and the optical axis, three axes of the crystal are determined by visual observation. The three principal indices obtained for 5893 Å are 1.550±0.010, 1.775±0.010, and 2.04±0.08. The absorption coefficients in the fundamental absorption tail are measured for polarized radiation along various crystal axes. The absorption coefficient measured along the b-axis is five times larger than that of the a-axis. The absorption along the c-axis is a little different from the others, but it is not so distinguished as is expected from the arrangement of the molecules. All the absorption coefficients decrease exponentially for wavelength.