Photoionization cross section of atomic and molecular oxygen
Photoionization cross sections of atomic oxygen and dissociative photoionization cross sections of molecular oxygen were measured from their respective thresholds to 120 angstrom by use of a photoionization mass spectrometer in conjunction with a spark light source. The photoionization cross sections O/sub 2//sup +/ parent ion and O/sup +/ fragment ion from neutral O/sup 2/ were obtained by a technique that eliminated the serious problem of identifying the true abundances of O/sup +/ ions. These ions are generally formed with considerable kinetic energy and, because most mass spectrometers discriminate against energetic ions, true O/sup +/ abundances are difficult to obtain. In the present work the relative cross sections for producing O/sup +/ ions are obtained and normalized against the total cross sections in a spectral region where dissociative ionization is not possible. The fragmentation cross sections for O/sup +/ were then obtained by subtraction of O/sub 2//sup +/ cross sections from the known total photoionization cross sections. The results are compared with the previously published measurements. The absolute photoionization cross section of atomic oxygen sigma/sub 8//sub +/ was measured at 304 A. The actual number density of oxygen atoms within the ionization region was obtained by measuring the fraction of 0/sup 2/ molecules dissociated. This sigma/sub +/ at 304 angstrom was used to convert the relative photoinization cross sections, measured as a function of wavelength using a calibrated photodiode, to absolute cross sections. The results are compared with previous measurements and calculated cross sections. angstrom Rydberg series converging to the OII /sup 4/P state was observed.
- Research Organization:
- Nebraska Univ., Lincoln (USA)
- OSTI ID:
- 5014236
- Country of Publication:
- United States
- Language:
- English
Similar Records
Absolute photoionization cross-section of the methyl radical.
EUV studies of N/sub 2/ and O/sub 2/ produced by low energy electron impact
Related Subjects
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ABUNDANCE
ATOMS
CATIONS
CHARGED PARTICLES
COMPARATIVE EVALUATIONS
CROSS SECTIONS
DISSOCIATION
ELEMENTS
ENERGY LEVELS
EXCITED STATES
IONIZATION
IONS
MASS SPECTROMETERS
MEASURING INSTRUMENTS
MOLECULAR IONS
MOLECULES
NONMETALS
OXYGEN
OXYGEN IONS
PHOTOIONIZATION
RYDBERG STATES
SPECTROMETERS