Dissociation of vibrationally-rotationally excited I2 (B 3Πou+)

The collisional dissociation of ${\mathrm{I}}_2{\mathrm{(B\hspace{0.17em}}}^3{\Pi }_{o_u^{+}})$ , initially excited near its dissociation limit in the presence of an excess of He, Ar, or Xe, has been studied, by trajectory calculations, as a function of the initial internal energy of the molecule. It was found that the percent dissociation is a steep function of temperature and total internal energy of ${\mathrm{I}}_2{\mathrm{(B\hspace{0.17em}}}^3{\Pi }_{o_u^{+}})$ . The rotational energy of the molecule is less effective than the vibrational energy in inducing collisional dissociation. The results are compared with several experiments which have recently been performed on these systems. The present calculations are in rough agreement with some experiments on the ${\mathrm{I}}_2{\mathrm{(B\hspace{0.17em}}}^3{\Pi }_{o_u^{+}})\mathrm{–Xe}$ system, but predict photochemical quantum yields for the ${\mathrm{I}}_2{\mathrm{(B\hspace{0.17em}}}^3{\Pi }_{o_u^{+}})\mathrm{–He}$ system which are smaller than those obtained experimentally. Recent fluorescence quenching experiments are also discussed in light of the present findings. Some reasons for the discrepancies and additional experimental tests are suggested.