Knowledge Bank

Molecular ions such as $S2-$, $S3-$ or $Se2-$ may be introduced in alkali halides by heating the crystals close to their melting point in S or Se vapor. These ions ar usually $paraelastic1$ above a characteristic temperature. We have measured their stress-induced linear dichroism and obtained detailed information regarding the identification of the ions, the assignment of their excited states and the ground state paraelastic relaxation. Measurements have been performed with a very sensitive apparatus and cover a wide range of temperatures $(300\circ$ $K-4\circ K$ ). The possibility of studying the relaxation of the excited state will be discussed.