scholarly journals An Experimental Determination of the Photo-ionization Cross-section of Atomic Hydrogen

Nature ◽  
1965 ◽  
Vol 207 (4995) ◽  
pp. 405-405 ◽  
Author(s):  
J. D. E. BEYNON
Keyword(s):  
Experimental Determination ◽  
Cross Section ◽  
Atomic Hydrogen ◽  
Ionization Cross Section ◽  
Ionization Cross ◽  
Photo Ionization

The photo-ionization cross-section of neon

1953 ◽  
Vol 220 (1140) ◽  
pp. 71-76 ◽  
Keyword(s):  
Cross Section ◽  
Ionization Cross Section ◽  
Wave Length ◽  
Grazing Incidence ◽  
Absorption Coefficients ◽  
Ionization Cross ◽  
Ionization Limit ◽  
Resonance Transitions ◽  
Photo Ionization ◽  
Dipole Length

The absorption of radiation of wave-length between 230 and 800 Å in neon was measured photometrically in a grazing incidence vacuum spectrograph. For wave-lengths longer than that corresponding to the first ionization limit the absorption coefficients were found to be zero except for photo-excitation of resonance transitions. Two sharp absorption edges were observed at 575 and 256 Å corresponding to the L 3 - and L 1 -edges respectively with a flat maximum between them. The photo-ionization cross-section at the first ionization limit was found to be 5⋅4 x 10 -18 cm 2 independent of the pressure between 50 and 500 μ ; this should be compared with the theoretical value of 5⋅8 x 10 -18 cm 2 obtained by Seaton using a dipole-length approximation. Between 575 and 400 Å the calculated and experimental curves agreed closely within the limits of measurement.

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