Stopping powers of N2 and O2 for protons from 4.0 to 13.0 MeV

Abstract

Stopping powers of N2 and O2 for protons from 4.0 to 13.0 MeV were measured with an accuracy of ±0.8% using a surface barrier silicon detector set inside a sealed gas cell. Energy loss in the gases was obtained from the peak shift of the proton pulse heights measured separately with and without gas filling. One-half of the experimental data obtained for molecules N2 and O2 was compared with that of experimental data for 4.4 MeV protons reported by Brolley and Ribe [Phys. Rev. 98 (1955)1112], the calculated values given in ICRU Report 49 [Stopping Powers and Ranges for Protons and Alpha Particles (International Commission on Radiation Units and Measurements, 1993)], and the values calculated by Andersen and Ziegler's formula [Hydrogen Stopping Powers and Ranges in All Elements (Pergamon, New York, 1977)] for atoms N and O. By analyzing the experimental results with the modified Bethe–Bloch formula that includes the Barkas correction term, we extracted the mean excitation energies, the I values, for N and O. The I values were compared with other reported values.