SPECTROSCOPIC STUDY OF MOLECULAR VIBRATIONAL-ENERGY IN PHASE-CHANGINGPROCESS

The vibrational energy of molecules in phase-changing processes was st udied by measuring the infrared absorption spectra using a Fourier tra nsform infrared (FTIR) spectrometer. IR spectra of (NO)(2)(nu(1), nu(4 )), CO2(nu(2), nu(3)), N2O(nu(1), nu(2), nu(3)), and C2H2(nu(3),nu(5)) in the gas, cluster, and solid phases were compared. Absorption bands of solid-phase molecules are blue or red shifted from those of gas-ph ase molecules: but those for the cluster phase are always blue shifted from those for the solid phase. This leads to two kinds of vibrationa l energy change when the phase changes from gas to solid : blue and re d shifts, and red and red shifts of the absorption bands. These result s can he explained in terms of the vibrational mechanisms of the epsil on, sigma, and m effects, which characterize the effective potential a nd mass of molecules.