Velocity Distribution of $\hbox {H}^{-}$ Ions in Low Temperature Hydrogen Plasma

A Monte Carlo solution of the Boltzmann equation is applied to the calculation of the velocity distribution of negative atomic ions H^- in uniform H/H₂ plasmas in a wide parameter range. Results are shown for the energy distribution n(epsiv), the 2-D velocity distribution, and the energy-dependent coefficients of the spherical harmonics expansion of its angular part, for different values of the reduced electric field E/N, the atomic fraction, and the H⁺ mole fraction. By increasing E/N or the atomic fraction at constant ion energy, the velocity distribution becomes highly anisotropic, and at same time, n(epsiv) features a suprathermal tail consistent with analytical results.