Direct Observations of Energy Transfer of Vibrationally Highly Excited Triatomic and Large Polyatomic Molecules

Average energies 〈ΔE〉 transferred per collision between vibrationally highly excited molecules and surrounding bath gases have been measured directly by using time resolved UV absorption spectroscopy after laser excitation. The experiments have been performed with highly excited CS2, SO2, toluene, azulene, ethyl‐, and isopropyl‐cycloheptatriene respectively. A great variety of up to 60 different bath gas molecules has been investigated. The temperature has been varied from 300 K to 1000 K. For the same bath gas molecule, the effect of the molecular size of the excited molecule on the 〈ΔE〉 values has been shown to be large at low degrees of excitation while it becomes almost negligible at high excitation energies. In contrast to that the molecular size of the deactivating molecule shows always a large effect on the 〈ΔE〉 values independent from the internal energy of the “hot” molecule. The reported temperature coefficients on the 〈ΔE〉 values are small in all cases. They vary from 〈ΔE〉αT−0.5 for n‐heptane deactivating “hot” toluene or “hot” CS2 molecules, to 〈ΔE〉αT0.0 for collisions of the noble gases with “hot” toluene, and to 〈ΔE〉αT1.0 for Ne deactivating “hot,” CS2.