Momentum transfer cross section of argon deduced from electron drift velocity data

The momentum transfer cross section of argon is deduced from experimental electron drift velocity data over the energy range from 0.02 to 100 eV. A method proposed earlier by Suzuki et al. (1989) which is improved by adding a minimising procedure of the fractional difference between calculated and experimental electron drift velocities, is used. In an E/N range below 0.1 Td, the electron drift velocity data of Robertson (1977) at a gas temperature of 89.6 K are analysed and the cross section for the low-energy region is deduced. The result shows that the Ramsauer-Townsend minimum is located at an electron energy of 0.23 eV with a magnitude of 9.35*10 -18 cm 2 . It is found that the present result is in excellent agreement with the theoretically determined values of Dasgupta and Bhatia (1985) and that the characteristic energy calculated from the present cross section agrees very well with the measurements of Milloy and Crompton (1982). In an E/N range above 0.1 Td, the experimental electron drift velocity data of Nakamura and Kurachi (1988) and Kucukarpaci and Lucas (1981) are analysed to deduce the cross section for the high-energy region. In order to obtain consistency among the present momentum transfer cross sections, ionisation cross sections by Krishnakumar and Srivastava (1988) and excitation cross sections by de Heer et al. (1979), reference is made to the ionisation coefficient data by Kruithof (1940), Abdulla et al. (1981) and Ishizuka et al. (1987). It is found that the peak of the momentum transfer cross section is located at an electron energy of 10 eV with a magnitude of 1.5*10 -15 cm 2 .