Accession Number : AD0625451

Title :   THE CESIUM IONIZATION CROSS SECTION FROM THRESHOLD TO 50 EV.,

Corporate Author : HUGHES RESEARCH LABS MALIBU CALIF

Personal Author(s) : Heil,H. ; Scott,B.

Report Date : NOV 1965

Pagination or Media Count : 27

Abstract : The ionization cross section sigma which was recently measured by Brink at 50 eV and above has been measured down to threshold in a Tate and Smith type apparatus designed for absolute measurements. The density in the collision space was determined by a surface ionization detector which permitted an over-all accuracy on the cross section of 10 percent. It was found: (1) sigma = 5.3 A squared at 50 eV. This is smaller by a factor of 1.8 than the above experiment and the theoretical values of the Gryzinski method - the discrepancy has not been explained. (2) The cross section near threshold is linear over a range of 0.8 eV with a slope of 2.2 A squared eV. Above 0.8 eV, it rises less than linearly. The initial slope is smaller by a factor of 3 than the earlier measurements of Nottingham. (3) Above 12 eV, excitation to the autoionizing states is seen, and above 18 eV, an additional contribution to the total cross section begins. The latter is due to ionization to an excited state of the ion. Cross sections for these two processes have been related to spectroscopic measurements of Beutler, et al., and have been separated from the basic ionizing channel. The curve for autoionization is resonant in nature with a maximum of 0.8 A squared. The ionization to the excited ion has an estimated maximum cross section of 1.5 A squared at 60 eV. (Author)

Descriptors :   (*CESIUM, IONIZATION), (*IONIZATION, PROBABILITY), EXCITATION, DISCHARGE TUBES, VOLTAGE, ATOMIC ENERGY LEVELS

Subject Categories : Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE