Excitation of highly excited states of atomic hydrogen in electron-detachment collisions of H- with H, H2, and Ar
Abstract
We have measured cross sections for formation of highly excited H (D) atoms in electron-detachment collisions of 2.8-60-keV/amu H- (D-) ions with H, H2, and Ar. The experimental technique employed a tungsten-tube furnace target and static electric field ionization. Excited hydrogen states with principal quantum number n between 12 and 28 were detected by measuring either the electrons or the protons resulting from field ionization. Electron detachment from H- is found to produce a 1/n3 distribution of highly excited levels over the entire energy range studied. Comparisons with low-n data indicate that 1/n3 scaling does not hold down to n=2 and n=3. The fraction of electron-detachment collisions that produce highly excited states has been measured as well. Above 20 keV the fraction is equal in H2 and H, yet the cross section for high excitation in H2 is twice as large as in H. This strongly suggests the validity of the independent-atom picture for H2 in these collisions above 20 keV. For direct comparison with electron capture, measurements have been performed with use of H+ projectiles. For H- collisions we have calculated the cross sections based on a simple high-energy model proposed by Drukarev which neglects electron correlation effects; poor agreement with experiment is found.
- Publication:
-
Physical Review A
- Pub Date:
- June 1985
- DOI:
- 10.1103/PhysRevA.31.3612
- Bibcode:
- 1985PhRvA..31.3612S
- Keywords:
-
- Atomic Excitations;
- Electron Transfer;
- Gas-Ion Interactions;
- Hydrogen Atoms;
- Ionic Collisions;
- Neutral Atoms;
- Argon;
- Atomic Energy Levels;
- Deuterium;
- Hydrogen Ions;
- Negative Ions;
- Quantum Numbers;
- Rydberg Series;
- Scattering Cross Sections;
- Atomic and Molecular Physics;
- 34.50.Fa;
- 34.50.Gb;
- Electronic excitation and ionization of atoms;
- Electronic excitation and ionization of molecules;
- intermediate molecular states