Frequency behavior of Raman coupling coefficient in glasses

The low-frequency Raman coupling coefficient C(nu) of 11 different glasses is evaluated. It is shown that the coupling coefficient demonstrates a universal linear frequency behavior C(nu)proportional to(nu/nu(BP)+B) near the boson peak maximum nu(BP). The frequency dependence of C(nu) allows us to separate the glasses studied into two groups: the first group has a frequency independent contribution Bsimilar to0.5, while the second one has Bsimilar to0. It was found that C(nu) demonstrates a superlinear behavior at very low frequencies. This observation suggests a vanishing of the coupling coefficient when frequency tends to zero.