Abstract
The drift velocity of electrons in helium at 300°K has been measured for values between 4× and 40 volt/cm-mm Hg. The data for volt/cm-mm Hg were obtained from measurements of electron transit time in a modernized version of the double shutter tube developed by Bradbury and Nielsen. The data at high were obtained from microwave measurements of the electron density in a positive column of a low-pressure discharge. The measured drift velocities are in good agreement with previous results in the range from to 3 volt/cm-mm Hg. At less than 3× volt/cm-mm Hg the electrons are essentially in thermal equilibrium with the gas. Margenau's theoretical expression for the drift velocity of electrons in a gas for which the cross section for momentum transfer is independent of electron energy is found to fit the data for volt/cm-mm Hg to the accuracy of measurements. The cross section which gives the best fit of the theory to the data is 6× .
- Received 10 August 1959
DOI:https://doi.org/10.1103/PhysRev.117.470
©1960 American Physical Society