Charge States of a Helium Beam in Hydrogen, Helium, Air, and Argon

Measurements have been made of the fractions of a helium beam in the ${\mathrm{He}}^0$, ${\mathrm{He}}^{+}$, and ${\mathrm{He}}^{++}$ charge states in the energy range of 100 kev to 480 kev for beams in hydrogen, helium, air, and argon. For the four gases, the ${\mathrm{He}}^0$ and ${\mathrm{He}}^{+}$ components are equal for helium energies of 148 kev, 145 kev, 98 kev, and 115 kev, respectively. The ratios of the electron loss to electron capture cross sections between ${\mathrm{He}}^{+}$ and ${\mathrm{He}}^{++}$ fitted a simple power dependence of $\left(\frac{{\sigma }_l}{{\sigma }_c}\right)\propto V^m$, where $V$ is the velocity of the helium in the beam and $m$ equals 6.1, 5.1, 5.2, and 6.3, respectively, for the four gases studied. For electron capture and electron loss between ${\mathrm{He}}^0$ and ${\mathrm{He}}^{+}$ the exponent $m$ varies from 2.6, 2.0, 2.8, and 3.4 at 100 kev to 4.0, 4.0, 4.3, and 5.1 at 450 kev.