Mechanical properties of anthracene crystals under illumination: Photoplastic effect

The mechanical properties of the photoplastic effect (PPE) in anthracene crystals were extensively studied. Detailed results of its dependence on strain rates ε̇, strain-rate sensitivity, temperature, and wavelength of exciting light have been obtained, and also the photomemory effect of PPE has been observed. Temperature dependence of PPE showed that the formation energy of physical dimers (photoinduced products) was estimated to be about 0.2 eV. Moreover, the strain-rate dependence of PPE indicated that the change in stress Δτs decreased with increasing strain rates, namely, the strain-rate sensitivity m=Δτs/Δ ln ε̇<0. In addition, the photomemory effect shows that physical dimers were stable at dislocation cores with a long life.