Temperature dependence of the optical homogeneous width of mesoporphyrin and its aggregate in polyvinylalcohol at 1.8–50 K

Abstract

The temperature dependence of the optical homogeneous width was investigated for mesoporphyrin and its aggregate doped in polyvinylalcohol from 1.8 to 50 K by means of persistent spectral hole burning and accumulated photon echo. Because the exponent of the temperature dependence changes around 10 K, there exist two dephasing mechanisms that are characteristic for amorphous polymers. At lower temperatures, phonon-assisted tunneling of two-level systems (TLS) is dominant. On the other hand, the Raman process of low-frequency phonons is dominant at higher temperatures.