Time-Resolved Electronic Spectroscopy To Examine Shock-Wave-Induced Changes in Anthracene Single Crystals

Shock-wave-induced electronic structure changes in anthracene single crystals were examined using time-resolved absorption and fluorescence spectroscopy. Crystals were subjected to stepwise loading normal to the (001) crystallographic plane to peak stresses between 2.5 and 6.0 GPa. Absorption experiments revealed (i) a monotonic shift of the absorption edge of the singlet state toward lower energies (red shift) and (ii) formation of a new band on the lower energy side of the red-shifted absorption edge. Furthermore, laser excitation to the new absorption band produced fluorescence with excimer-like characteristics. The combined absorption and fluorescence results indicate the formation of new electronic states as a consequence of shock-wave compression and the resulting plastic deformation. The new states are attributed to dimer-type defects formed in shocked anthracene crystals.