The excitation-energy, polarization, pressure, and temperature dependences of Raman scattering spectra have been measured for the RB 6 crystals ( R = Ca 2 + , La 3 + , Ce 3 + , Pr 3 + , Sm 2.6 + , Gd 3 + , Dy 3 + , and Yb 2 + ). In the Raman spectra, the extra peaks have been clearly observed at around 200 cm - 1 , except for the Raman-active phonons and CEF excitations. The extra peaks show anomalous behavior in the temperature, polarization, and lattice parameter dependences. These anomalous behaviors originate from the vibration of the rare-earth ions in octahedral B 6 cage, and the extra peaks can be assigned as the second-order Raman excitations of T 1 u phonon at Brillouin zone boundary. In the results of pressure dependence, the valence of all Sm ions in SmB 6 becomes trivalent above 20 GPa at room temperature.