Photoionization and ion cyclotron resonance studies of the reaction of vibrationally excitedC2H2plus;ions with H2

摘要

The reactionC2H2plus;plus;H2rarr;C2H3plus;plus;Hhas been studied using ion cyclotron resonance and photoionization mass spectrometric techniques. At thermal kinetic energies, the cross section for the reaction is near zero for ground state reactants but increases rapidly with increasing vibrational energy in theC2H2plus;ions. The ratio of the cross sections for ions in the ngr;2equals; 1 and ngr;2equals; 2 states is approximately 1:2, respectively. Some reaction is observed at photoionization energies below the theshold for formation of ngr;2equals; 1 ions owing to reaction of thermally excited ions and neutrals. For the distribution of vibrational energies inC2H2plus;ions formed by electron impact at 15 eV, the rate constant for the reaction is 6.3plusmn;1.8times;10minus;11cm3sol;sec. Exchange of hydrogen atoms in nonreactive collisions betweenC2H2plus;ions and D2molecules has also been observed. An upper limit ofDgr; Hflpar;C2H3plus;rpar;equals;267thinsp;kcalsol;moleis obtained.