Accession Number : AD0813425

Title :   ELECTRON-IONIZATION CROSS SECTIONS.

Descriptive Note : Semiannual progress rept. no. 7, 16 Jun-15 Dec 66,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE

Personal Author(s) : Crawford, Charles K.

Report Date : 15 DEC 1966

Pagination or Media Count : 26

Abstract : Absolute electron ionization cross sections have been measured for silver using a single crossed beam method. Absolute values for the formation of Ag(+) and Ag(++) were determined at 100 volts electron energy by integrating the ion current produced in a carefully controlled intersection of an electron beam with a beam of monatomic silver. Absolute values at other electron energies were then obtained using ratios of mass spectrometer peak heights. The cross section values at 75 electron volts were determined to be 4.65 x 10 to the -16th power sq cm for Ag(+) and 4.75 x 10 to the -17th power sq cm for Ag(++). The value for Ag(+) agrees to within experimental error with the extrapolated experimental values of other workers, but disagrees with theoretical predictions. A new Knudsen cell assembly was designed and constructed, and many tests were made on its performance. Thus two Knudsen cell assemblies are now available for making cross section measurements though only the new one can be used with the multiple-crossed-beam technique. A new ultrahigh vacuum system with a multiflange test chamber, gauging, and an automatic pressure control system, was obtained for use in studying the modulating ionizer. Modulating ionizer tests were initiated. (Author)

Descriptors :   *IONIZATION), (*SILVER, ELECTRONS, MASS SPECTROSCOPY, SPECTRUM ANALYZERS, HEAT SHIELDS, ELECTRON BEAMS, NUCLEAR CROSS SECTIONS.

Subject Categories : Atomic and Molecular Physics and Spectroscopy
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE