Electron Drift and Diffusion in Parahydrogen at 77°K

Abstract

This paper reports a series of experiments to measure electron diffusion and drift in pure parahydrogen at 77° K. Tables of data are given for the electron drift velocity W in the range 1.2 X l0⁻¹⁹ ≤ E/N ≤ 9.5 x l0⁻¹⁷ V cm² and for the ratio of diffusion coefficient to mobility D/μ for 2 X 10⁻²⁰ ≤ E/N ≤ 6 X 10⁻¹⁷ V cm². As expected, these data are indistinguishable from the data for normal hydrogen in the thermal region and at the higher values of E/N where vibrational excitation is the dominant process controlling the electron energy distribution. However, at intermediate values of E/N, the values of W and D/μ differ by more than 10 and 20% respectively from the corresponding values in normal hydrogen, demonstrating the influence of the difference in the statistical weights of the rotational levels in the two gases.