The effect of crystalline phase on the fluorescence characteristics of solid cyclohexane and bicyclohexyl

Emission from cyclohexane and bicyclohexyl solids has been found to critically depend on their crystalline structure. The emission spectrum of cyclohexane suddenly blue-shifts 2900 cm^?1 on cooling below its solid—solid phase transition temperature (?87.1°C). The bicyclohexyl emission intensity sharply decreases on freezing to solid and then again sharply recovers at a heretofore unreported phase transition temperature (≈ 0°C) with the spectrum 2500 cm^?1 blue-shifted from that of the liquid. The results are discussed utilizing the partial Rydberg nature of the excited cycloalkane states.