The Absorption of Slow Hydrogen Positive Rays in Hydrogen

An experimental method for studying the absorption of slow hydrogen positive rays in hydrogen is described. The absorption coefficients of ${\mathrm{H}}^{+}$, ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_3^{+}$ in hydrogen were measured in the region between 60 and 850 volts. The absorption coefficient of ${\mathrm{H}}_3^{+}$ was found to be smaller than that of ${\mathrm{H}}_2^{+}$ and very much nearer the absorption coefficient of ${\mathrm{H}}^{+}$ in magnitude. The absorption coefficient of ${\mathrm{H}}_2^{+}$ decreased from a value of 40 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$ at 60 volts velocity to 20 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$ at 850 volts and that of ${\mathrm{H}}_3^{+}$ decreased from 17 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$ at 60 volts to 12 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$ at 500 volts. The absorption coefficient of ${\mathrm{H}}^{+}$ remained nearly constant at 8 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$, about one-half the kinetic theory value. No minimum of absorption was observed for any of the ions in the region investigated. Qualitative experiments upon the nature of the absorbing process indicate that the absorption of ${\mathrm{H}}_2^{+}$ is probably due to neutralization while scattering is probably the most important factor in the absorption of ${\mathrm{H}}^{+}$ and ${\mathrm{H}}_3^{+}$ ions.