Spectroscopic Study of Molecular Vibrational Energy in Phase-Changing Process

The vibrational energy of molecules in phase-changing processes was studied by measuring the infrared absorption spectra using a Fourier transform infrared(FTIR)spectrometer. IR spectra of(NO)2(ν1, ν4), CO2(ν2, ν3), N2O(ν1, ν2, ν3), and C2H2(ν3, ν5)in the gas, cluster, and solid phases were compared. Absorption bands of solid-phase molecules are blue or red shifted from those of gas-phase molecules : but those for the cluster phase are always blue shifted from those for the solid phase. This leads to two kinds of vibrational energy change when the phase changes from gas to solid : blue and red shifts, and red and red shifts of the absorption bands. These results can be explained in terms of the vibrational mechanisms of the ε, σ, and m effects, which characterize the effective potential and mass of molecules.