The Scattering of Low Velocity Hydrogen Ions in Helium

The low velocity scattering of H+, H2+ and H3+ in helium was measured. No neutralization was experienced and the potential laws were evaluated. For H+ in the range 3 to 130 volts (ra = 2.66 to 0.55A), V=−1.36×10−18r2.27. For H2+ in the range 4 to 50 volts (ra = 1.67 to 0.87A), V=−1.47×10−32r4. In the range 50 to 120 volts (ra = 0.87 to 0.66A), V=−1.31×10−32r4. For H3+ in the range 1.5 to 14 volts (ra = 2.22 to 1.59A), V=−3.9×10−53r6.68. In the range 14 to 65 volts (ra = 1.59 to 1.12A), V=−1.06×10−24r4.46. In the range 65 to 130 volts (ra = 1.12 to 0.89A),V=−4.83×10−24r3.01. The interaction of H+ in He shows the effect of the chemical combination to form HeH+. Assuming an equilibrium distance of 0.8A, the interaction energy is 3.27 ev. H2+ in He follows the law expected on the basis of the interaction of the charge on an ion with a polarizable molecule. The interaction of H3+ with He is more complex. An exact analytical treatment of the scattering problem shows that n, calculated from the experimental data by the previously used general approximate method, is correct. An exact numerical solution is given for the case n = 4 and several values of the mass ratio of ion to molecule and values of fc obtained, where fcKa = Ke. A less laborious method of calculating f, involving a simplifying assumption, is used; and it is shown that fc = f well within the precision of the experiments. A similar method is used to calculate f for the same mass ratios and n = 0, 1, and 2. A family of curves is obtained from which values of f can be interpolated for other values of n and mass ratio.