The proton stopping cross section of gases at low energies

• Main Author: Reynolds, Harlan Kendall
• Format: Others
• Published: 1953
• Online Access: https://thesis.library.caltech.edu/1688/1/Reynolds_hk_1953.pdf; Reynolds, Harlan Kendall (1953) The proton stopping cross section of gases at low energies. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XGRY-HH72. https://resolver.caltech.edu/CaltechETD:etd-05092003-080704 <https://resolver.caltech.edu/CaltechETD:etd-05092003-080704>

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Proton stopping cross sections for gases and vapors were measured in the energy range 30 to 600 kev. A beam of protons was passed through a chamber with thin aluminum end walls containing the gas or vapor to be measured. The energy of the beam was measured before and after passing through the chamber and with and without the gas in the beam in order to measure the energy loss in the foils and in the gas. The beam was accelerated by an electrostatic generator, and the beam energies measured by an electrostatic analyzer and magnetic spectrometer. The substances measured were air, H[subscript 2], He, N[subscript 2], O[subscript 2], Ne, A, Kr, Xe, H[subscript 2]O, CO[subscript 2], CH[subscript 4], C[subscript 2]H[subscript 2], C[subscript 2]H[subscript 4], C[subscript 6]H[subscript 6], NH[subscript 3], NO, and N[subscript 2]O. Bragg's rule was tested by comparison of NH[subscript 3] with N[subscript 2]/2 + 3H[subscript 2]/2, NO with N[subscript 2]/2 + O[subscript 2]/2 etc., for H[subscript 2]O, NH[subscript 3], NO, and N[subscript 2]O, and found to be valid above 150 kev, except for NO. On the assumption of Bragg's rule, the stopping cross section of carbon was calculated from the data on the hydrocarbons, CO[subscript 2], and oxygen and hydrogen. The results were consistent for energies above 100 kev. The mean excitation potentials calculated from the measured stopping cross sections are: Oxygen, I = 103[...]5 ev; nitrogen, I = 89.5[...]4 ev; carbon, I = 7.24[...]3 ev; and helium, I = 32.8[...]1.5 ev.