Time-dependent processes in polyatomic molecules during and after intense infrared irradiation

Abstract

The time-dependent processes occurring in polyatomic molecules during and after intense infrared irradiation, for example in infrared photochemistry, are discussed in terms of underlying structures in the absorption spectra. Origins of homogeneous and inhomogeneous spectral structures are identified in high-resolution spectra of small molecules (CF₃H and CF₃CCH). Temperature-dependent bandshapes of large polyatomic molecules, (CF₃)₃CH and (CF₃)₃C—CCH are evaluated in terms of the most relevant parameters of the vibrational structures, using a new method. The bandshape parameters can be interpreted in terms of intramolecular vibrational processes on the picosecond and subpicosecond time-scales. Characteristic differences in the dynamic coupling behaviour of the acetylenic CH stretching and the saturated CH stretching vibrations are identified in the fundamental and the overtone spectra.