Publication costs assisted by Hahn-Meitner-lnstitut fur Kerntorschung Berlin GmbH Simultaneous optical absorption and polarographic current measurements were carried out to investigate the free radicals formed in the pulse irradiation of N2O saturated 10-1 M ethylene glycol solutions. In the pH range from 3 to 7, only the 1,2-dihydroxyethyl radical could be observed. It disappears with 2k = 8.7 X 10* M'1 sec-1. Below pH 3, the dehydration of this radical to yield the formylmethyl radical was observed. The equilibrium constant of the protonization of 1,2-dihydroxyethyl and the decay constant of the protonated radical were found to be 1.8 X 10~a M (or pK = 0.74) and 8.6 X 10s sec-1, respectively.The formylmethyl radical disappears with 2k = 9 X 10s M*1 sec-1. In alkaline solutions, a rapid dehydration also occurs. The diffusion-controlled reaction OH-+ OH-CHCH2OH H2O + -QCHCH2OH and the rapid decay -OCHCH2OH -* OH--I-OCHCH2 are postulated. The short time polarograms of 1,2-dihydroxyethyl and formylmethyl differ significantly. 1,2-Dihydroxyethy 1 is oxidized at the mercury electrode at potentials more positive than -1.0 V (us. saturated calomel electrode) and reduced at more negative potentials. Formylmethyl is oxidized beyond -0.1 V and reduced at potentials more negative than -0.3 V. The 1,2-dihydroxyethyl radical therefore is a much stronger reducing agent than the formylmethyl radical.

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Quartet excited halogen atoms produced in the electron pulse irradiation of rare gases containing halogenated compounds J. Chem. Phys. 103, 999 (1995); 10.1063/1.470700 Fluorocarbon high density plasmas. VIII. Study of the ion flux composition at the substrate in electron cyclotron resonance etching processes using fluorocarbon gases Rate constants for electron attachment to some highly reactive fluorocarbon gases have been determined by microwave conductometric methods. Initial ionization of the gas was by pulse radiolysis with 2.8 MeV electrons. To facilitate measurements on very reactive compounds a method has been developed which is applicable when the electron half-life is < I J.Lsec. This method uses the amplitude of the steady-state response of the detector during the pulse and the rate of production of electrons based on measurements on the nonattaching buffer gas alone. This steady-state method was tested on mixtures of CFzCl z or SF 6 in C3H8 and was shown to agree with direct measurements of the decay of the electron concentration. With propane as the buffer gas the method is applicable where the electron half-life is greater than about 0.5 J.Lsec at I torr total pressure. At higher pressures of attaching gas decreases in apparent rate constant were observed which could be attributed to electron reaction before complete thermalization. Values for thermal attachment rate constants (cm 3 molecule-I. sec-I) at 25·C found in this work are 1.3 X 10-9 for CF 2 CI 2 ; 1.2 X 10-8 for cyclo-C 4 F 8 , 1.4 X 10-7 for cyc10-C 4 F 6' and 4.9 X 10-8 for C4F8-2. In comparison to these values that for cyclo-C3F6 was determined to be < 3 X 10-14 . Perfluoropropylene was found to undergo a transition from three-to two-body behavior at high pressures of buffer gas, and the rate constant values imply a negative ion lifetime near I J.lsec. The limiting value of the two-body rate constant was found to be 3 X 10-10 cm 3 molecule-I. sec-I.