Nobuhiro Yamanaka

High-Precision Calculation of the Energy Levels and Auger Decay Rates of the Metastable States of the Antiprotonic Helium Atoms

We precisely calculated the energy levels and the Auger decay rates of the antiprotonic helium atoms with the coupled rearrangement channel method and the complex-coordinate-rotation method. Calculated transition frequencies were in excellent agreement with observed values. This agreement gives best limit of the antiproton mass with 5×10−8 uncertainty.

Time-Dependent Coupled-Channel Calculations of Muon-Transfer Cross Sections in Muonic Deuterium and Triton Collisions

A time-dependent coupled channel (TDCC) method has been developed to study rearrangement reactions in few-body Coulomb systems. We apply the TDCC method to muon transfer in muonic deuterium and triton collisions. The muon-transfer cross section (S-wave) is calculated for triton energies of 100 eV–3 keV. The present result is in good agreement with the previous calculation with the coupled rearrangement channel method [Hyp. Interact.82 (1993), 45]. We also illustrate time evolution of wave functions to understand qualitatively the muon-transfer reaction.

Calculation of mass polarization for the and states in Li-like ions

Mass polarization arises from a correlation between electronic momenta. In Li-like systems, the effect of core electron correlation dominates. The mass polarization for the and states in B III-Ne VIII is calculated with the use of configuration interaction (CI) wavefunctions. Its dependence on the nuclear charge Z and the atomic states is then studied. The effect of core electron correlation is clearly illustrated with a simple CI wavefunction.

Channel-coupling array theory for Coulomb three-body dynamics: Antiproton capture by hydrogen atoms

A theory of channel coupling array is developed for rearrangement reactions in Coulomb three-body systems. Inhomogeneous coupled differential equations for the three Faddeev components are derived and directly solved with the technique of complex rotation in the exterior region. This method is applied to slow antiproton collisions with hydrogen atoms. It is found for a collision energy of 6.8 eV that the antiproton is captured dominantly into protonium states with the principal quantum numbers around 40 and that the electron is released with energies around 2 eV. The electron velocity thereby obtained is much higher than the incident velocity of the antiproton. Time-dependent wave-packet propagation of the Faddeev components is also investigated to illustrate the peculiar dynamics.

Direct Positron Annihilation and Positronium Formation

Positrons in a gas annihilate directly during a collision with target matter, or indirectly via positronium (Ps) formation followed by its decay. The cross sections of direct annihilation and Ps formation for hydrogen atom targets are calculated with the time-dependent coupled channel method. The result of the Ps-formation cross section is in good agreement with previous results. The direct annihilation cross section is found to be enhanced in energies around 10 eV well above the Ps-formation threshold. This enhancement is shown to be due to temporal positron capture with electronic excitation in the atom.

Time-Dependent Coupled-Channel Calculations of the Annihilation Rate in Positron-Hydrogen Collisions

We calculate the positron annihilation rate in positron-hydrogen collisions for positron energies of 250 meV-6.5 eV using a time-dependent coupled channel method. A semiempirical model recently proposed in Phys. Rev. Lett. 79 (1997), 2241 predicts that the annihilation rate prominently enhances through virtual positronium formation as the positron energy approaches the positronium formation threshold (6.8 eV) from 4 eV. We illustrate time evolution of wave functions to show that such a prominent enhancement of the annihilation rate is not found and contribution of virtual positronium formation is not important below 6.5 eV.

Mass polarization effect in He-like ions

The mass polarization effect, which is important for isotope shifts in light atoms, is calculated for the 1s2 1S, 1s2s 3S and 1s2p 3P states in the He-like isoelectronic sequence, He I-Ne IX, to study the transition dependence of the electron correlation effect. Results are carefully compared with previous results. The ratio of the mass polarization effect to the transition energy is found to be proportional to Z for the 1s2s 3S-1s2p 3P transition, while to Z-1 for the 1s2 1S-1s2s 3S and 1s2 1S-1s2p 3P transitions, where Z is the nuclear charge. As Z increases, the mass polarization effect dominates isotope shifts for the 1s2s 3S-1s2p 3P transition.

Coupled Rearrangement Channel Calculation of the Hyperfine Structure of the dtμ Molecule

Hyperfine structure splittings are calculated for the J = v = 1 state of the dtμ molecule. The splittings are determined by the accurate three-body wave function obtained by coupled rearrangement channel method using the updated physical constants. The result obtained is in good agreement with the previous calculation within ∼0.07 meV. The discrepancy is due to the accuracy of the three-body wave function.

Formulation of nuclear polarization correction with the Feynman photon propagator

The leading order process of the nuclear polarization (NP) is formulated with the Feynman photon propagator. The present treatment incorporates the whole contributions due to the Coulomb and transverse interactions as well as their interference in the Coulomb gauge. An explicit formula is given in the point-nucleus limit for hydrogen-like heavy ions. The numerical method is also discussed.

Hyperfine anomaly for the ground state of 9Be

The Fermi contact parameter which represents hyperfine structure (hfs) has been accurately calculated for the ground state of the 9Be+ ion in a previous paper. In the present paper, the calculated parameter is compared with a high precision measurement to derive the hfs anomaly (the Bohr-Weisskopf effect), which is caused by nuclear magnetization distribution. The obtained hfs anomaly shows a satisfactory agreement with the result of a nuclear shell model calculation.