| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2005: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
Low-energy antiproton collisions with atomic or molecular ions was investigated using a wave-packet-propagation full-quantum-mechanical method or a quantum-classical hybrid (i.e., semiclassical) approximation. It is found that the adiabatic picture (i.e., Born-Oppenheinmer separation) is appropriate in a large sense.
In the case of atomic ion targets, the antiproton capture is a typical non-adiabatic process because the electron must be emitted in this process, and hence occurs less frequently. However, even at very low energies, the capture probability is in fact small but finite still for large angular momenta. Correspondingly, the cross section for the non-adiabatic process diverges in the zero energy limit. This happens due to the peculiarity that the Coulomb force range is longer than the centrifugal one. Importance of a Rydberg series of resonances in the capture process is also 0found.
In the case of molecular ion targets, the adiabatic condition is satisfied much better because t
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he electron can escape from the antiproton by forming a neutral atom or molecule. At the same the, the formation of aniti porotonic atoms becomes possible even in the adiabatic approximation. For the molecular ion targets, the antiprotonic atom formation can be treated as the collisions on a single adiabatic (Born-Oppenheimer) potential energy surface (PES), in the same manner as chemical reaction problems. The PES was caclculated for teh antiproton and hydrogen molecular ion system. A classicla trajectory Monte Carlo method was applied to the collision calculation. It is found that the dissociative dynamics plays a critical role in antiptotonic hydrogen (protonium) formation, the consequently the molecular target is much more effective in antiproton capture than the atomic target.
I carried out the calculation also for collisions of hydrogen molecular ions with negative muons and kaons, and investigated the mass effect on the reaction dynamis. It is found that the antiproton capture has a remarkable mass dependence. This is clearly in contrast to the negligible mass dependence. This is clearly in contrast to the negligiblemass dependence of the antiproton capture by atom in which the non-adiabatic coupling plays a dominant role. Less
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