Energy and Angular Distributions of Secondary Electrons from 5-100-keV-Proton Collisions with Hydrogen and Nitrogen Molecules

Cross sections for the ejection of electrons from hydrogen and nitrogen by protons have been measured as a function of the energy and angle of ejection of the electrons at incident proton energies of 5-70 keV and 100 keV for hydrogen. The range of angles measured was 10-160° and the electron energy range was 1.5-300 eV. The doubly differential cross sections were also integrated over angle, over electron energy, or over both to obtain singly differential and total cross sections for electron production. Average electron energies were also calculated from the data. The angular distributions of electrons are peaked in the forward direction but become more isotropic as the proton energy decreases. Nitrogen yields a more isotropic distribution than hydrogen. In this range of proton energies the cross sections integrated over angle are found to fall off approximately exponentially with electron energy, and a simple empirical equation has been found that describes the singly differential and total cross sections within a factor of 2 for several targets. A theoretical interpretation of this result in terms of the molecular promotion model is given in which Meyerhof\u27s method of calculating cross sections for K-shell excitation is applied for the first time to the ionization of outer shells of atoms

The Rainbow and the Achromatic Telescope: Two Case Studies

From the history of science we can learn not only some science and some history, but also something about how science is done and how it interacts with technology. The First case study chosen illustrates the development of an understanding of a phenomenon of nature-one that has been observed with awe and wonder for as long as man has walked the Earth, but has only been well understood in the last 200 years. Some of the greatest thinkers of all time have worked on the problems of the rainbow. The second study shows how an important invention became possible only when nature was well enough understood. It also illustrates the interaction of science and technology, that is, between understanding and application

Energy Spectra of Auto-Ionizing Electrons in Oxygen

Experimental and theoretical data are presented showing the energy spectra of auto-ionizing electrons from atomic oxygen. The experimental data were obtained by bombarding oxygen gas with 100-keV H+ and He+ ions; the theoretical results were obtained in a close-coupling calculation which coupled the 4S, 2D, and 2P terms of the ground-state configuration of O+ in electron-O+ scattering

Auger Electrons from Argon with Energies 150-210 eV Produced by H\u3csup\u3e+\u3c/sup\u3e and H\u3csub\u3e2\u3c/sub\u3e\u3csup\u3e\u3c/sup\u3e Impacts

Secondary electrons in the energy range 150-210 eV produced by 125-300-keV H+ and H2+ impacts on argon gas are measured as a function of their energy and angle of emission. Discrete line spectra are due to Auger transitions from L2 and L3 vacancy states as well as satellite transitions from multivacancy states. The widths, energies, and branching ratios of the L2 and L3 vacancy states are presented. Widths of these states are appreciably greater than those obtained with electron impact excitation. This can be attributed to the recoil velocities of the target atom and to the presence of the proton in the vicinity of the emitting atom. The angular distribution of Auger electrons is found to be nearly isotropic, in marked contrast to electrons in the continum spectrum. The cross sections for the production of L2,3 and L3 vacancy states are determined as a function of impact energy

Angular and Energy Distribution of Cross Sections for Electron Production by 50-300-keV-Proton Impacts on N\u3csub\u3e2\u3c/sub\u3e, O\u3csub\u3e2\u3c/sub\u3e, Ne, and Ar

Cross sections differential in angle and ejection energy for electron production by proton impact on nitrogen, oxygen, neon, and argon have been measured using electrostatic analysis and counting of individual electrons. The range of proton energies was 50-300 keV, the angles ranged from 10° to 160°, and the electron energies were measured from 1.5 to 1057 eV. Integrations over angle and/or electron energy yielded singly differential and total electron production cross sections. Our total cross sections for oxygen fall halfway between previous data of deHeer et al. and Hooper et al., but our argon cross sections agree better with deHeer et al. Cross sections for electron ejection in the backward hemisphere are much greater for these multishell targets than for hydrogen and helium. The momentum-energy conservation hump which was prominent in hydrogen is less conspicuous for these gases

Auger Electrons from Argon with Energies 150-210 eV Produced by H\u3csup\u3e+\u3c/sup\u3e and H\u3csub\u3e2\u3c/sub\u3e\u3csup\u3e\u3c/sup\u3e Impacts

Secondary electrons in the energy range 150-210 eV produced by 125-300-keV H+ and H2+ impacts on argon gas are measured as a function of their energy and angle of emission. Discrete line spectra are due to Auger transitions from L2 and L3 vacancy states as well as satellite transitions from multivacancy states. The widths, energies, and branching ratios of the L2 and L3 vacancy states are presented. Widths of these states are appreciably greater than those obtained with electron impact excitation. This can be attributed to the recoil velocities of the target atom and to the presence of the proton in the vicinity of the emitting atom. The angular distribution of Auger electrons is found to be nearly isotropic, in marked contrast to electrons in the continum spectrum. The cross sections for the production of L2,3 and L3 vacancy states are determined as a function of impact energy

Energy and Angular Distribution of Electrons Ejected from Hydrogen and Helium Gas by Protons

Differential cross sections for ejection of secondary electrons of various energies at various angles were measured for hydrogen gas bombarded by 100-keV protons and for helium gas bombarded by 50-, l00-, and 150-keV protons. The range of angles investigated was 10° to 160° and the range of electron energies was 1 to 500 eV. A unique fixed-port, double-walled scattering chamber was used. Electrons were counted by an electron multiplier after passing through a 127° electrostatic analyzer. The efficiency of the detector was determined by replacing the analyzer and multiplier by a Faraday cup and making absolute measurements of cross sections differential only in angle. Comparison with the integral of the differential cross sections over all electron energies gave a value of about 78% for the efficiency. As a function of electron energy the cross sections decrease monotonically above about 2.5 eV and are uncertain below this value. All cross sections decrease monotonically with an increase in angle but are relatively constant above about 110°. The differential cross sections have been integrated in various ways to obtain distributions over electron energy and angle, total cross sections for ionization, average energies of the ejected electrons, and the stopping cross sections due to ionization. Comparisons are made with other experimental results and with theoretical treatments by the Born approximation and the Gryzinski classical theory

Experimental Evidence for the Mechanism of Charge Transfer into Continuum States

We have observed a prominent peak in the energy spectrum of electrons ejected in the forward direction from helium bombarded by protons ranging in energy from 100 to 300 keV. The peak occurs at an ejected-electron velocity equal to the velocity of the incident proton. The experimental results verify the existence of the mechanism of charge transfer into continuum states of the incident ion

Absolute Doubly Differential Cross Sections for Ejection of Secondary Electrons from Gases by Electron Impact. II. 100-500-eV Electrons on Neon, Argon, Molecular Hydrogen, and Molecular Nitrogen

Absolute doubly differential cross sections for secondary electron production by electron impact have been measured for static gas targets of neon, argon, hydrogen, and nitrogen. Electron impact energies were from 100 to 500 eV. An electrostatic analyzer was used to analyze secondary electrons with energies between 4 eV and the primary electron energy minus the first ionization potential of the target. Angles of emission were 10° to 150°. The present data agree well with the data of Opal, Beaty, and Peterson at 90° but, as was observed previously for helium, the agreement becomes increasingly poorer for larger and smaller angles. This angular disagreement, which is independent of target gas and impact energy, is approximately given by a+(1-a) sin θ, where a=0.10±0.12. Previously we compared the experimental data of Opal, Beaty, and Peterson with calculations by Manson for helium and obtained a similar correction but with a=0.53. Recent Born-approximation calculations of Manson are compared with our 500- eV argon data. The calculations reproduce the angular distributions of the measured cross sections quite well for small secondary-electron energies. For intermediate energies the agreement is still quite good near the momentum-conservation peak but poorer for large scattering angles

Angular and Energy Distribution of Cross Sections for Electron Production by 50-300-keV-Proton Impacts on N\u3csub\u3e2\u3c/sub\u3e, O\u3csub\u3e2\u3c/sub\u3e, Ne, and Ar

Cross sections differential in angle and ejection energy for electron production by proton impact on nitrogen, oxygen, neon, and argon have been measured using electrostatic analysis and counting of individual electrons. The range of proton energies was 50-300 keV, the angles ranged from 10° to 160°, and the electron energies were measured from 1.5 to 1057 eV. Integrations over angle and/or electron energy yielded singly differential and total electron production cross sections. Our total cross sections for oxygen fall halfway between previous data of deHeer et al. and Hooper et al., but our argon cross sections agree better with deHeer et al. Cross sections for electron ejection in the backward hemisphere are much greater for these multishell targets than for hydrogen and helium. The momentum-energy conservation hump which was prominent in hydrogen is less conspicuous for these gases