Effect of solidified gas layers on the reflection spectra of anthracene crystals

Measurements are reported for the b-polarized reflection spectrum of anthracene crystals off the (001) face coated with solidified layers of some permanent gases. In the wavelength range 4020 to 3800 Å spanning the 0-0 vibronic transition to the first electronic state there are several narrow minima attributed to surface transitions. The minimum I at 3954 Å is shifted 11 Å to longer wavelengths by solidified air, whilst the rest of the spectrum exhibits little or no change. This red-shift, expecied for transitions to surface exciton states, is new evidence for the assignment of minimum I as such. In addition a new minimum at ca. 3985 Å has been observed on the long wavelength edge of the 0-0b reflection band, very close to minimum II at 3984 Å. © 1976.