Infrared multiphoton excitation of CF3I. II. Collisional energy transfer of vibrationally highly excited CF3I

Abstract

Energy transfer of vibrationally highly excited CF3I molecules (E≈18 000 cm−1) in collisions with argon, propane, and octane was studied using hot UV absorption spectroscopy of CF3I. the preparation of the excited CF3I was achieved by IR multiphoton absorption which, under the conditions applied, produces a narrow initial energy distribution of CF3I near to the dissociation energy. The average energies 〈ΔE〉 transferred per collision were found to be proportional to E for the bath gases propane and octane; they showed a stronger increase with energy at low excitation energies in the bath gas argon. The energy dependence of 〈ΔE〉, therefore, is not only governed by the properties of the excited molecule (e.g., its density of states) but also by features of the collision partner (e.g., the magnitude of 〈ΔE〉). At energies near to the dissociation energy for all colliders, 〈ΔE〉 was found to approach values similar to those obtained from single UV photon excitation experiments with highly excited triatomic and large polyatomic molecules.