Temperature Dependence of Width and Position of the Lowest Singlet-Singlet Transition in Crystalline Tetracene

Linewidth and position of the lowest singlet-singlet transition in crystalline tetracene are investigated in the temperature range 130 °K to room-temperature. It is found that below 200 °K the linewidth is temperature independent. The values for both Davydov components are 450 ± 50 cm−1 (‖b) and 30± 50 cm−1 (⊥b), i.e., at least twice as much as for crystalline anthracene. Upon slow cooling the redshift of the absorption peaks, which is reported to occur below 70° K, is found to occur almost continuously in the temperature range 300 to 180 °K. This raises doubts whether it results from a first order phase transition of the crystal lattice.