ROTATIONAL GATEWAY FOR THE VIBRATIONAL-ENERGY TRANSFER FROM EXCITED NONLINEAR TRIATOMIC-MOLECULES

Classical trajectory calculations for the collisional energy transfer between vibrationally excited SO2 molecules and thermal Ar and He atom s are analyzed with respect to a partitioning of the total energy tran sfer between the ''rotational'' and ''vibrational'' components. It is shown that for the case studied (total energy of SO2 being 10 kcal/mol ), ''vibrational'' energy transfer is governed by energy transfer to t he active rotation. Therefore, the active rotation represents a gatewa y for vibrational energy transfer provided that during the time betwee n successive collisions the intramolecular vibrational relaxation ensu res microcanonical equipartitioning of the molecular energy. A compari son with previous trajectory calculations (Schranz, H. W.; Tree, J, J. Phys. Chem. 1986, 90, 6168) on the same system indicates that, at hig her total energies of SO2, direct vibrational deactivation becomes mor e effective than the transfer via the rotational gateway.