Photoelectric Observation of the Rate of Recombination of Iodine Atoms

摘要

The rate of the homogeneous threehyphen;body recombination of iodine atoms,Iplus;Iplus;Mrarr;I2plus;M,thinsp;dlsqb;I2rsqb;sol;dtequals;klsqb;Irsqb;2lsqb;Mrsqb;, is measured. A short intense pulse of light from a flash lamp dissociates 1ndash;9 percent of theca1018iodine molecules in a 200hyphen;cc cell, and the subsequent recombination of iodine atoms is followed by fast photoelectric techniques.The measured values ofkat room temperature are 4.2(plusmn;0.4)times;109liter2molesminus;2secminus;1(argon), 58(plusmn;4)times;109(neopentane), 65(plusmn;6)times;109(pentane). The value for neopentane is the same at 200deg;C.The large values of the recombination rate constants indicate that an important recombining process consists of a ``sticky'' collision between an I atom and an M molecule or atom, leading to the formation of a complex IM, which reacts with a second I atom. The lifetimes of the collision complexes are estimated.The rates of the reverse process, the dissociation of I2by collision with M, are calculated; the prehyphen;exponential factors are extraordinarily large.The extinction coefficients of gaseous iodine have been remeasured.