  The temperature dependence of in plane optical conductivity has been
investigated for Ca0.86Pr0.14Fe2As2 which shows a structural transition from
tetragonal (T) to collapsed tetragonal(cT) phase at TcT=73 K. Upon entering the
cT phase, drastic change characterized by the formation of a midinfrared peak
near 3200 cm-1(0.4 eV) in the optical conductivity is observed.Analysis of the
spectral weight reveals reduced electron correlation after the cT phase
transition.Based on the calculated band structure and simulated optical
conductivity, we attribute the new feature around 0.4 eV to the formation of
interlayer As-As bond. The As-As bond strongly affects the Fe-As
hybridizations, and in turn, drastically changes the Ca0.86Pr0.14Fe2As2 into a
nonmagnetic Fermi liquid system without bulk superconductivity in the cT phase.
