Isotope effect in charge-transfer collisions of slow H{sup +} and D{sup +} ions with H{sub 2}, HD, and D{sub 2} molecules
- Department of Science, Kinki University, Higashi-Osaka, Osaka, 577-8502 (Japan)
Marked characteristics in charge-transfer cross sections between collisions of H{sup +} and D{sup +} ions with H{sub 2}, HD, and D{sub 2} molecules, the so-called isotope effect, are observed in the energy range from 0.18 to 1.0 keV/u. The observed cross-section ratios {sigma}(D{sup +}+D{sub 2})/{sigma}(H{sup +}+H{sub 2}) of charge transfer in D{sup +}+D{sub 2} and in H{sup +}+H{sub 2} collisions are found to be 0.665 at 0.18 keV/u and gradually increases, finally approaching unity at higher energies. Similar behavior and magnitude within the error bars of the cross-section ratios {sigma}(H{sup +}+HD)/{sigma}(H{sup +}+H{sub 2}) and {sigma}(D{sup +}+HD)/{sigma}(H{sup +}+H{sub 2}) have been observed, although the present calculation predicts a sizable difference for heteronuclear molecules. The cross section differences due to the target isotope effect are pronounced even in the high-eV to low-keV region. On the other hand, charge-transfer cross-section ratios for the same target but different projectile isotopes, e.g., {sigma}(H{sup +}+HD)/{sigma}(D{sup +}+HD) and {sigma}(D{sup +}+D{sub 2})/{sigma}(H{sup +}+D{sub 2}), are constant near unity, which indicates a minor role of collision-induced vibrations as compared to the target vibrational spacing. It is understood that the isotope effect in the charge transfer of ion-molecule collisions originates from the combination of a small offset in binding and vibrational energies and the different spaces occupied by the wave functions of the target H{sub 2}, HD, and D{sub 2} molecules.
- OSTI ID:
- 20646224
- Journal Information:
- Physical Review. A, Vol. 70, Issue 5; Other Information: DOI: 10.1103/PhysRevA.70.052710; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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