W. C. Wang

Dissociative electron attachment to some chlorine‐containing molecules

The electron‐attachment rate constants of CH3Cl, C2H5Cl, and C2H3Cl in N2 and Ar were measured as a function of reduced electric field (E/N). These data and the previous data of SOCl2 and CCl2F2 were converted to the electron‐attachment cross sections as a function of electron energy. The present results are compared with existing fragmentary data. The dissociative electron‐attachment processes of the studied molecules are discussed.

Low‐energy electron attachment to BCl3

The rate constants of low‐energy electron attachment to BCl3 diluted in N2 are measured as a function of E/N at 1–11 Td, corresponding to mean electron energies at 0.4–1.0 eV. The negative ions produced by hollow‐cathode discharges of either pure BCl3 or mixtures of BCl3 in N2 are mass analyzed to identify the products of electron attachment to BCl3. Only Cl− ion is found in the discharge media, although BCl−3 is observed at the applied voltage significantly lower than the breakdown voltage. The electron attachment processes of BCl3 are discussed.

Electron attachment rate constants of SO2 and CS2 in Ar, N2, and CH4 at varied E/N

The electron attachment rate constants of SO2 and CS2 in the buffer gases of Ar, N2, and CH4 (150 to 530 Torr) at various E/N (1–16 Td) were measured by a parallel‐plate drift‐tube electron‐swarm technique. The electrons were produced by irradiating the cathode with KrF laser photons. For the SO2–Ar mixture, the electron attachment rate constant of SO2 increases with increasing E/N and is independent of Ar pressure. For SO2 in N2 and CH4, the electron attachment rates decrease with increasing E/N and increase with increasing buffer gas pressure. For CS2 in N2 and CH4, the electron attachment rates increase with increasing CS2 and buffer gas pressures and decrease with increasing E/N. The electron attachment to SO2 and CS2 in the buffer gases of N2 and CH4 is a three‐body process. The collisional‐stabilized rates of ‘‘temporary’’ negative compound ions SO−*2 and CS−*2 by various gases are investigated.

Attachment of low‐energy electrons to HCl

The electron‐attachment rate constants of HCl diluted in Ar and N2 were measured as a function of the reduced electric field E/N. These data were converted to the electron‐attachment cross section of HCl using the electron‐energy distribution functions of pure Ar and N2. The dependence of the electron‐attachment rate constant and the mean electron energy on the fraction of HCl in each buffer gas was investigated. A comparison of the current result with both available experimental data and theoretical calculations is made.

CH2OH+O2 reaction rate constant measured by detecting HO2 from photofragment emission

The HO2 radical was produced in a flow tube by the Cl+CH3OH→HCl+CH2OH and CH2OH+O2→HO2+CH2O reactions. HO2 was detected by the OH(A 2∑+→X 2Π) photofragment emission produced by photodissociative excitation of HO2 in the vacuum ultraviolet region. Using this detection method, the rate constant for the CH2OH and O2 reaction was measured to be (1.4±0.4)×10−12 cm3/s.

Electron attachment to H2O in Ar, N2, and CH4 in electric field

The attachment of electrons to H2O in Ar, N2 or CH4 is investigated using a parallel‐plate drift‐tube apparatus. Electrons are produced either by irradiation of the cathode with ArF laser photons or by two‐photon‐ionization of a trace of trimethylamine in a buffer gas. The transient voltage pulses induced by the electron motion between the electrodes are observed. The electron attachment rate of H2O is determined from the ratio of transient voltage with and without H2O added to the buffer gas. The measured electron attachment rate constants of H2O in Ar increase with E/N from 2 to 15 Td. Electron attachment due to the formation of ‘‘temporary’’ negative ions in the H2O–N2 and H2O–CH4 mixture were observed. The lifetime of the negative ion was determined to be about 200 ns, whose nature is discussed. The ‘‘apparent’’ electron attachment rate constants for the formation of ‘‘temporary’’ negative ions in the H2O–CH4 gas mixture are measured for E/N from 1 to 20 Td. The electron drift velocities for the gas m...

Electron attachment rate constants of HBr, CH3Br, and C2H5Br in N2 and Ar

The electron attachment rate constants of bromine compounds in the buffer gases of N2 and Ar (∼250 Torr) were measured as a function of E/N (or mean electron energy). The measured electron attachment rate constants of HBr, CH3Br, and C2H5Br show maximum values of 1.05×10−9, 1.08×10−11, and 9.3×10−11 cm3/s at mean electron energies of 0.55, 0.4, and 0.8 eV, respectively. The electron drift velocities for the gas mixtures of CH3Br in N2 and Ar were also measured.

Electron attachment rate constants of SOCl2 in Ar, N2, and CH4

The electron attachment rate constants of SOCl2 in the buffer gases of Ar, N2, and CH4 (150 to 500 Torr) at various E/N (1–15 Td) were measured by a parallel‐plate drift‐tube electron‐swarm technique. Electrons were produced by irradiating the cathode with KrF laser photons. For the SOCl2–Ar mixture, the electron attachment rate constant has a maximum value of 6.2×10−10 cm3/s at E/N=4 Td. For SOCl2 in N2, the electron attachment rate constant is 1.25×10−9 cm3/s at E/N=1.3 Td, and decreases with increasing E/N. For SOCl2 in CH4, the electron attachment rate constant is 4.8×10−9 cm3/s at E/N=1 Td, and decreases with increasing E/N. For every gas mixture studied, the electron attachment rate constant is independent of buffer gas pressure, indicating that the electron attachment to SOCl2 is due to a dissociative process. The electron attachment processes in the studied gas mixtures are discussed.

Shortening of electron conduction pulses by electron attacher C3F8 in Ar, N2, and CH4

The attachment rate constants of C3F8 in the buffer gases of Ar, N2, and CH4 are measured using a parallel‐plate drift‐tube apparatus. The dependences of the electron drift velocities on the contents of C3F8 in various buffer gases are investigated. Electrons are produced by irradiating the cathode with ArF laser photons. The transient voltage pulses induced by the electron motion are observed. We find that the C3F8‐CH4 mixture has the desirable characteristics of both electron drift velocity and attachment rate constant for the application of diffuse‐discharge opening switches.

Two‐photon‐ionization coefficients of CS2, SO2, and (CH3)3N

Electrons produced by two‐photon ionization of CS2, SO2, and (CH3)3N in N2 and CH4 buffer gases at 193 nm were investigated using a parallel‐plate drift‐tube apparatus. At a low charge density, the transient voltage induced by electron motion between the electrodes is proportional to the gas pressure and the square of laser power. The two‐photon‐ionization coefficients measured from the number of electrons produced are 3.3×10−27, 8.3×10−30, and 1.7×10−27 cm4/W for CS2, SO2, and (CH3)3N, respectively. The coefficient for (CH3)3N agrees with the earlier value measured by ion current. At a high charge density, the number of electrons observed deviates from the square dependence of laser power. The numbers of ions and electrons are greatly reduced by charge recombination whose reaction rate is enhanced in the presence of space charge.