COLLISION-INDUCED DISSOCIATION OF CS2+ - HEAT OF FORMATION OF THE CS RADICAL

Guided-ion beam mass spectrometry is used to probe the reaction of CS2+ with Xe as a function of ion kinetic energy from thermal to 16 eV.S+, CS+, and Xe+ are the only observed reaction products. Formation of S+(4S(u)) is observed, even though it is spin forbidden, providing evidence for the importance of spin-orbit coupling in the dissociation of CS2+. The threshold for formation of S+ + CS, 4.74 +/- 0.04 eV, leads to a heat of formation of the CS radical DELTA(f)H0(0)(CS) of 65.8 +/- 0.9 kcal/mol. From this value, we derive the bond energies D0(0)(CS) = 169.8 +/- 0.9 kcal/mol, D0(0)(S-CS) = 103.8 +/- 0.9 kcal/mol, and D0(0)(O-CS) = 158.7 +/- 0.9 kcal/mol. The onset for production of CS+ by collision-induced dissociation of CS2+ is observed at 6.16 +/- 0.07, 0.40 eV above the thermodynamic threshold, but coincident with the threshold for excitation to the C approximately state of CS2+. The cross section for charge transfer to form Xe+ displays a threshold of almost-equal-to 2 eV, corresponding to the difference in ionization energies of Xe and CS2. This process is significantly enhanced at higher energies where the concomitant dissociation of CS2 to CS and S becomes accessible.