Low-energy excitations in noncrystalline arsenic trioxide

The liquid to glass transition for arsenic trioxide has been studied by performing low-frequency Raman scattering in the temperature range 300–770 K. For this glass forming system the light scattering intensity ratio of the relaxational $\text{(ω<15\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}})$ to the vibrational (Boson peak) contribution is much higher than that expected for low fragility systems near the glass transition temperature. A possible explanation for this unexpected feature is given by employing a structural model that is also able to interpret the hypersound propagation and absorption peculiarities found previously in this system. The depolarization ratio, in the quasi-elastic frequency region for different oxide glasses, is associated with local microstructural transformations causing fast relaxations in these systems. The Boson peak region is discussed in the context of different models and current theoretical approaches for the glass transition.