Molecular Stopping Cross Sections of Air, N2, Kr, Co2 and CH4 for Alpha Particles

Abstract

A method was developed to measure the stopping powers of gases for alpha particles using a semiconductor detector mounted opposite a natural source of particles in a gas chamber. By varying the gas pressure and taking an energy loss measurement at each pressure, the molecular stopping cross sections as a function of alpha particle energy were calculated. Experimental data are given for air, N2, A, Kr, CO2 and CH4 for alpha particles in the energy range 300 keV–5 meV. The estimated probable error in the cross sections ranges from approximately 4 per cent at the highest energies to approximately 12 per cent at the lowest energies.