Measurement of electron-transport coefficients in O by a double-shutter drift-tube method

A double-shutter drift-tube technique based on an analysis of arrival-time spectra has been applied to experimentally determine three electron-transport coefficients in , namely the ratio of the effective ionization coefficient to the gas density , the mean-arrival-time drift velocity and the product of the longitudinal electron-diffusion coefficient and the gas density over a wide range of 7-5000 Td . The result shows that the obtained is in excellent agreement with that of the steady-state Townsend experiment at of 500-5000 Td. In a lower range, however, some difference is observed. As a result of examination, it is revealed that the difference approximately gives the true attachment coefficient under the present experimental conditions. The determined takes an almost constant value at Td and, in the other ranges, monotonically increases with . Its profile differs from available experimental data at Td but is rather close to theoretically derived data. The ratio of the longitudinal diffusion coefficient to the electron mobility is also deduced. Furthermore, the result analysed by the conventional time-of-flight method is presented for comparison.