Quasi-free scattering in the ionization and destruction of hydrogen and helium Rydberg atoms in collision with neutral targets
Hydrogen and helium Rydberg atoms (H** and He**), with principal quantum number n ranging from 10 to 20, have been used in collision experiments from 1 to 40 keV/amu. These were produced by electron capture in a charge-exchange cell and analyzed by ionization in a modulated electric field combined with phase-sensitive detection. Three experiments have been conducted. In the first, spectra of the band of H and He Rydberg states from electron capture were produced by the modulated field technique and compared. Considerable differences were found between the two. Both types of spectra were analyzed with calculations of Stark energies and field ionization rates. Attempts were made to simulate the spectra using this information and some assumptions about the state distribution produced in the electron capture. In the second experiment, destruction cross sections for H** incident on N[sub 2], Ar, and SF[sub 6] were measured. This was a further test of the independent-particle model for Rydberg atom scattering; in this model, the atom is destroyed by quasi-free scattering of either the ionic core or the outer electron. Already proven valid for n = 20-35, this has been extended to n as low as 10, as measurements with n = 10 showed full compliance with the model. In the third experiment, not only destruction cross sections but also ionization cross sections for H** and He** incident on Xe, AR, and N[sub 2] were measured. The ionization measurement is a more sensitive test of the quasi-free scattering of the Rydberg electron. This was especially important for the Xe and Ar targets, which exhibits a Ramsauer-Townsend minimum in their free-electron scattering cross sections. The quasi-free Rydberg electron should reproduce these data. Unmistakable deviations from the quasi-free prediction were seen in Xe and N[sub 2] but not in Ar. This represents the first measurement of a breakdown of the Independent Particle Model for fast Rydberg atom scattering.
- Research Organization:
- Wesleyan Univ., Middletown, CT (United States)
- OSTI ID:
- 7233002
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOM-ATOM COLLISIONS
CAPTURE
COLLISIONS
DIRECT REACTIONS
ELECTRON CAPTURE
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
GASES
HELIUM
HYDROGEN
IONIZATION
MATHEMATICAL MODELS
NONMETALS
NUCLEAR REACTIONS
PARTICLE MODELS
QUASI-ELASTIC SCATTERING
QUASI-FREE REACTIONS
RARE GASES
RYDBERG STATES
SCATTERING
SINGLE-PARTICLE MODEL