High-pressure FT IR measurements of crystalline methylene chloride up to 120 kbar in the diamond anvil cell

The FT IR spectra of pressure-induced crystalline CH₂Cl₂ at room temperature were measured at hydrostatic pressures up to 120 kbar in the diamond anvil cell. The pressure dependences of the internal modes (ν₃, ν₉, ν₈, and ν₂) are reported and compared with the result of Raman scattering measurements. The discontinuity of the slope (dν/dP) at ≈ 45 kbar for the ν₉ antisymmetric CCl streching mode indicates the pressure-induced second-order phase transition which seems to be triggered by the interaction between the ν₉ mode and the ν₃ symmetric CCl stretching mode.