Vibrational relaxation of CH2I2 in solution:: Excitation level dependence

Transient electronic absorption monitors the flow of vibrational energy in methylene iodide (CH2I2) following excitation of five C-H stretch and stretch-bend modes ranging in energy from 3000 to 9000 cm(-1). Intramolecular vibrational relaxation (IVR) occurs through a mechanism that is predominantly state-specific at the C-H stretch fundamental but closer to the statistical limit at higher excitation levels. The IVR times change with the excitation energy between the fundamental and first C-H stretch overtone but are constant above the overtone. The intermolecular energy transfer (IET) times depend only weakly on the initial excitation level. Both the IVR and the IET times depend on the solvent [CCl4, CDCl3, C6D6, C6H6, or (CD3)(2)CO] and its interaction strength, yet there is no energy level dependence of the solvent influence. (C) 2003 American Institute of Physics.