| A pulse radiolysis facility for the study of fast chemical kinetics in the gas phase, based on a Febetron 706 electron beam accelerator, has been established at the University of Florida Radiation Chemistry Laboratories. Maximum accelerator specifications are 600 keV electron energy, 8000 amps, and 10 joules per pulse; pulse width is 3 nanoseconds (FWHM). Hardware has been developed for studies in the ultraviolet and vacuum ultraviolet regions using absorption spectrophotometry.; Parameters relevant to a linear electron beam initiated atomic iodine laser, which would lase on the transition 5('2)P(,1/2) (I*) (--->) 5('2)P(,3/2) (I), have been investigated by pulse radiolysis. Kinetic data for the parent compound quenching of I* were obtained by variation of the parent compound pressure at constant buffer gas pressure and observing I* decay rates versus time. Deactivation rate constants for the perfluoroalkyl iodides were found to be much lower than for alkyl iodides (in cm('3)/molec s): CH(,3)I, 2.0 (+OR-) 0.1 x 10('-13); C(,2)H(,5)I, 5.0 (+OR-) 0.3 x 10('-13); CF(,3)I, 8.8 (+OR-) 1.5 x 10('-16); C(,2)F(,5)I, 9.7 (+OR-) 1.0 x 10('-15); i-C(,3)F(,7)I, 1.7 (+OR-) 0.1 x 10('-15); C(,4)F(,9)I, 1.8 (+OR-) 0.1 x 10('-14).; The extent of population inversion was investigated by measuring initial excited state and ground state atomic iodine concentrations and calculating the branching ratio, {lcub}I*{rcub}(,0)/{lcub}I{rcub}(,0): CH(,3)I, 2.7; CF(,3)I, 3.8; C(,2)F(,5)I, 2.7; i-C(,3)F(,7)I, 3.2; C(,4)F(,9)I, 1.8. Perfluoromethyl iodide showed the largest population inversion from electron beam irradiation.; Using formation of O(,3) from O(,2) as the dosimeter (G = 13.8 molecules/100 eV for ozone), energy deposited per electron pulse in 750 torr O(,2) was 7.3 x 10('18) eV/g. Spectrophotometric detection of ozone utilized the 253.7 nm Hg line.; The rate of formation of ground vibrational state ozone in the pulse radiolysis of oxygen was followed using the 253.7 nm Hg line. The rate of formation was found to be nearly second-order with a rate constant of 4.1 (+OR-) 0.4 x 10('-15) cm('3)/molec s. It is formed from direct combination of oxygen atoms and oxygen molecules and from collisional quenching of vibrationally excited ozone and/or an electronically excited ozone precursor, probably ozone (('3)B(,2)). |
