Stopping Cross Sections of Gases for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>Particles from 0.3 to 2 MeV

Abstract

Stopping cross sections for $\ensuremath{\alpha}$ 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 ${(\mathrm{C}{\mathrm{H}}_{2})}_{3}$. 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.