Temperature dependence of the vibrational modes of MoO3

Transmission and reflection spectra of orthorhombic MoO3 crystals have been measured from 20 to 600 cm−1 as a function of temperature. Reflectivity spectra are fitted with a four-parameter dispersion model based on the factorized form of the complex dielectric function. The temperature dependence of the frequency is analysed using the anharmonic model with two- and three-phonon decay functions. This temperature dependence is dominated by the cubic term in the anharmonic model.