Positron-impact ionization, positronium formation, and electronic excitation cross sections for diatomic molecules
- Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0319 (United States)
Absolute measurements are presented for the positron-impact cross sections for positronium formation, direct ionization, and total ionization of the diatomic molecules N{sub 2}, CO, and O{sub 2}, in the range of energies from threshold to 90 eV. Cross sections for the electronic excitation of the a {sup 1}{pi} and a{sup '} {sup 1}{sigma} state in N{sub 2} and the A {sup 1}{pi} state in CO near threshold are also presented. The experiment uses a cold, trap-based positron beam and the technique of studying positron scattering in a strong magnetic field. In O{sub 2}, a feature previously seen in the total ionization cross section is observed in both the positronium formation and total ionization cross sections. The possible origin of this feature and its relationship to positron-induced dissociation is discussed. In N{sub 2}, the near-threshold electronic excitation cross section is larger than that for positronium formation. This likely explains the relatively high efficiency of this molecule when used for buffer-gas positron trapping.
- OSTI ID:
- 20786312
- Journal Information:
- Physical Review. A, Vol. 72, Issue 6; Other Information: DOI: 10.1103/PhysRevA.72.062713; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
Similar Records
Total-cross-section measurements for positrons and electrons colliding with H/sub 2/, N/sub 2/, and CO/sub 2/
Inseparable positron annihilation and positronium formation in positron-atom collisions: Description in terms of an absorption potential