Ionizing Collisions of Metastable Helium Atoms in Gases

Journal Article · Sun Apr 01 04:00:00 EST 1962 · Dissertation Abstr.

DOI:https://doi.org/10.1063/1.1732469· OSTI ID:4818262

Sholette, W P

A molecular beam method was employed to measure ionization cross sections for collisions of metastable helium atoms in various gases. A cylindrical beam of therraal energy metastable atoms, produced by electron bombardment of helium gas, was passed through a scattering chamber containing the scattering gas at pressures of the order of 10/sup -3/ mm Hg. Ions produced in the gas by inelastic collisions were detected at a metal electrode, and unscattered or elastically scattered metastable atoms were detected by observing the electrons they ejected from metal surfaces. From the ratios of the ion current to the total current, ionization cross sections in A/sup 2/, sigma /sub i/, were calculated. Ionization cross sections were measured for each of the metastable states of helium in argon. krypton, xenon, hydrogen, oxygen, nitrogen, and carbon monoxide. Within the experimental error of the measurements, the cross sections for the 2/sup 1/S and 2/sup 3/S states of helium were the same in all cases except that of hydrogen. The results are discussed in terms of energetically possible ionization processes for each gas, the energy excess, DELTA E for these processes, and the size of the scattering atoms or molecules. For the rare gases, the results indicated that the size of the struck particle is the primary factor in deterraining the cross section for ionization, rather than the energy excess. In the case of the diatomic molecules, an additional consideration, that of the number and type of ionization processes possible, was also found to be important.

• Research Organization: Univ. of Florida, Gainesville
• Sponsoring Organization: USDOE
• NSA Number: NSA-16-024296
• OSTI ID: 4818262
• Journal Information: Dissertation Abstr., Journal Name: Dissertation Abstr. Vol. Vol: 22
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ARGON
ATOMS
BEAMS
CARBON MONOXIDE
CROSS SECTIONS
DETECTION
ELASTIC SCATTERING
ELECTRODES
ELECTRON BEAMS
ELECTRONS
ENERGY
ENERGY LEVELS
ENERGY RANGE
EV RANGE
HELIUM
HYDROGEN
INELASTIC SCATTERING
INTERACTIONS
ION SOURCES
IONIZATION
IONS
KRYPTON
MEASURED VALUES
METALS
METASTABLE STATES
MOLECULES
NITROGEN
OXYGEN
PHYSICS
PRODUCTION
SCATTERING
SECONDARY EMISSION
SURFACES
VACUUM
VOLUME
XENON