Dissociative recombination at elevated temperatures. II. Comparison between theory and experiment in neon and argon afterglows

Finite Automorphism Groups of Torsion-Free Abelian Groups of Finite Rank

“…The pressure-driven shock tube used in this work was structurally similar to that described previously by Cunningham and Hobson ( 1972). Tu undertake measurements of recombination rate coefficients at elevated temperatures between 500 and 3000 K, non-ionising shock waves (Mach 1.6 to Mach 6) were propagated into downstream pressures of the helium-neon mixtures between 2 and 6Torr.…”

“…Tu undertake measurements of recombination rate coefficients at elevated temperatures between 500 and 3000 K, non-ionising shock waves (Mach 1.6 to Mach 6) were propagated into downstream pressures of the helium-neon mixtures between 2 and 6Torr. Depending upon the helium partial pressure and hence speed of sound in the mixture, different combinations of diaphragm thicknesses (0.1 to 0.3 mm) and driver gas (helium, argon or nitrogen) were used to vary the Mach number (Cunningham and Hobson 1972). The thin diaphragm was ruptured by over-pressurisation and the attendant shock wave travelled along a 7 m long Pyrex flow channel of 4 cm internal diameter.…”

“…The transit time of the slice between the electrode region and the first of the probe stations exceeded 1 ms, which allowed translational temperature equilibrium to be established between the ions, electrons and neutrals in the plasma slice. The saturated current to each probe was captured using a 1 ps channel transient digitiser (Gutherie et a1 1987) and was related to the ion density in the slice along the flow channel using the reduction procedure discussed by Cunningham and Hobson (1972). Knowledge of the shock velocity was then used to construct reciprocal number density against time plots for individual shock waves.…”

“…Figure 3 displays recombination data obtained using pure neon (0% He) as the test gas. The different symbols on this plot represent the shock tube measurements of Cunningham and Hobson (1972) and results obtained using the apparatus constructed for this investigation. Both data sets are seen to be in excellent agreement throughout the common temperature range examined.…”

“…The shock-tube technique developed by Cunningham and Hobson (1972) was used and mixtures containing 0,25,49 and 75% helium seeded in neon were examined. Mass spectrometric studies of the kinetic processes occurring in afterglows containing helium and neon by Veatch and Oskam (1972) indicate that, at pressures exceeding a few Torr, the ion undergoing recombination will be Ne: in each of the mixtures.…”