Cluster Ion Thermal Decomposition (I):  Experimental Kinetics Study and ab Initio Calculations for HSO₄⁻(H₂SO₄)x(HNO₃)y

Rate coefficients for the thermal decomposition of cluster ions of the type HSO 4 - (H 2 SO 4 ) x for x = 1−5, HSO 4 - (HNO 3 ) y for y = 1, 2 and HSO 4 - H 2 SO 4 HNO 3 were measured as functions of temperature and pressure in a quadrupole ion trap. The measured decomposition kinetics are in the low-pressure limit or in the fall-off region between the low and high-pressure limits. Moments of inertia and vibrational frequencies of the clusters were obtained via ab initio HF/6-31+G(d) geometry optimizations. Bond energies were determined from analysis of the second-order rate coefficient data for the cluster ions with kinetics in the low-pressure limit. Upper limits of the bond energies were derived for the clusters with kinetics in the fall-off region.