Excitation of the b /sup 1/. sigma. /sup +//sub g/ state of O/sub 2/ by low energy electrons
Rate coefficients for excitation of the b /sup 1/..sigma../sup +//sub g/ state of O/sub 2/ by low energy electrons have been measured using a drift tube technique. The time dependence of the absolute intensity of the 762 nm band emission was measured for O/sub 2/ densities between 10/sup 16/ and 2 x 10/sup 18/ molecules/cm/sup 3/. When corrected for electron attachment, ionization, and metastable diffusion, the number of b /sup 1/..sigma../sup +//sub g/ molecules produced per centimeter of electron drift and per O/sub 2/ molecule calculated from the 762 nm emission varied from 1.3 x 10/sup -18/ cm/sup 2/ at E/N=5 x 10/sup -17/V cm/sup 2/ to 2.1 x 10/sup -16/ cm/sup 2/ at E/N=2 x 10/sup -15/V cm/sup 2/. These values of electric field to oxygen density ratio E/N correspond to mean electron energies of 0.75 and 6 eV, respectively. Measured decay constants for the 762 nm radiation yield a value for the product of the diffusion coefficient and the O/sub 2/ density of (5.0 +- 0.3) x 10/sup 8/ cm/sup -1/ sec/sup -1/ and a quenching coefficient for the b /sup 1/..sigma../sup +//sub g/ state of (3.9 +- 0.2) x 10/sup -17/ cm/sup 3/ sec/sup -1/. Comparison of measured excitation coefficients with values calculated using a recommended set of electron collision cross sections for O/sub 2/ show that the cross sections for direct excitation of the b /sup 1/..sigma../sup +//sub g/ state are accurate near threshold and suggest that essentially all of the O/sub 2/ molecules excited to levels at and above 1.63 eV result in the formation of molecules in the b /sup 1/..sigma../sup +//sub g/ state.
- Research Organization:
- Joint Institute for Laboratory Astrophysics, National Bureau of Standards and University of Colorado, Boulder, Colorado 80309
- OSTI ID:
- 6752848
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 69:3; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
COLLISIONS
CRYOGENIC FLUIDS
ELECTRON COLLISIONS
ELECTRON-MOLECULE COLLISIONS
ELEMENTS
EMISSION SPECTRA
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EV RANGE
EV RANGE 01-10
EXCITATION
FLUIDS
MOLECULE COLLISIONS
NONMETALS
OXYGEN
SPECTRA