Electron Attachment-Detachment Processes in Dry Air

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Abstract
The pulses due to electron avalanches released in dry air from a cathode of a uniform field gap (6 cm) by photoelectrons in a time interval of about 40 nsec are investigated. Using a new method of evaluation which yields simpler formulas, the attachment coefficient η for formation of unstable negative ions and the mean lifetime τ of these ions are determined. In the pressure range 4–60 Torr, η/p is independent of pressure and increases in the E/p range 33–53 V cm−1 Torr−1 from 0.006 cm−1 Torr−1 to 0.017 cm−1 Torr−1. In the same pressure range, τp is independent of pressure and decreases from 35 μsec Torr to about 2 μsec Torr. Our results confirm the earlier assumption of one prevailing kind of unstable negative ion. The value of η/p agrees with that obtained earlier at E/p close to 40 V cm−1 Torr−1. A distinct variation of η/p with E/p, not reported earlier, is obtained.