Stopping Cross Sections of Gases forαParticles from 0.3 to 2 MeV

Abstract

Stopping cross sections for $\alpha$ particles have been measured in a differentially pumped gas-cell system from 300 keV to 2 MeV in 13 gaseous compounds: ${\mathrm{H}}_2$, ${\mathrm{N}}_2$, ${\mathrm{O}}_2$, N${\mathrm{H}}_3$, ${\mathrm{N}}_2$O, CO, C${\mathrm{O}}_2$, C${\mathrm{H}}_4$, ${\mathrm{C}}_2$ ${\mathrm{H}}_2$, ${\mathrm{C}}_2$ ${\mathrm{H}}_4$, ${\mathrm{C}}_2$ ${\mathrm{H}}_6$, ${\mathrm{C}}_3$ ${\mathrm{H}}_6$, and ${\left(\mathrm{C}{\mathrm{H}}_2\right)}_3$. The probable random error of the measurements varies from 1 to 2%. Independent measurements have also been made with a sealed gas cell in a scattering chamber for ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$, and are found to agree with the differentially pumped gas-cell measurements to within 2.7%. Tests for water-vapor adsorption on thin carbon films used by Chu and Powers are also made and show that a deviation no greater than 3.8% would occur in their original $\frac{\mathrm{dE}}{\mathrm{dx}}$ measurements.