Temperature Dependence of Optical Spectra for the CDW Gap and Optical Phonons in BaBiO₃

We have studied the temperature dependence of the optical spectra for the CDW gap and optical phonons in a single crystal of BaBiO_3 and a film deposited by laser ablation. The integrated optical conductivity for optical phonons decreases rapidly with increasing temperature above 150 K, while the single-particle excitation across the CDW gap remains constant.