Lorentz ionization of H(1s) is investigated by classical trajectory Monte Carlo (CTMC) simulation. The effect of the transverse magnetic field on the considered process is analyzed in terms of the time evolution of interactions in the system, total electron energy, and electron trajectories. A classical mechanism for the ionization is found, where the variation of the kinetic energy of the nuclei is found to be important in the process. Compared with the results of tunneling ionization, the classical mechanism becomes more and more important with the increase of the velocity of the H-atom or the strength of the magnetic field.
Using the reaction microscope technique,we have performed kinematically complete measurements for single capture in He+collisions with He at 30 and 100 keV[1].The state-selective and the angular-differential cross sections were extracted from the experimental data and compared with our theoretical calculations based on the dynamic-screening classical trajectory Monte Carlo method(dCTMC).The measured recoil-ion longitudinal momentum distributions are shown in Fig.1.
The cooling of heavy ions can provide high-quality beams that are especially important for high-precisionexperimental nuclear and atomic physics. The laser cooling of relativistic C3+ ion beams at the experimental coolerstorage ring (CSRe) is being currently prepared at Institute of Modern Physics (IMP) in Lanzhou. An electroncyclotron resonance ion source (ECRIS) will be used to produce C3+ ion beams. Meanwhile, O4+ ions could alsobe produced due to residual gas because of the same mass-to-charge ratio. Therefore, both C3+ and O4+ ion beamswill be injected and circulate in a storage ring during the laser cooling experiment at the same time. A higher ratioof C3+ ions will lead to a better result for the laser cooling experiment.
The collision induced dissociation (CID) of H+2 ion colliding with He target has been measured by Williams andDunbar[1] and Suzuki et al.[2] in the keV energy region. In Ref. [1], the CID cross sections decrease monotonouslywith decreasing energy. But the energy dependency of the CID results in Ref. [2] is different with that in Ref. [1].At energies below 1 keV, no experimental results are available for integral cross sections. On the theoretical side,Furlan and Russek[3] have investigated the electron capture (EC), CID and excitation processes in the few keVenergy region. Their calculations are performed by the straight-line trajectory method based on the ab initiomolecular structure. A three-state approximation is employed in their calculations. Their CID cross sections areseveral times smaller than the experimental results. We present the quantum-mechanical molecular orbital closecoupling (QMOCC) calculations[4] for the CID process of the H+2 + He collision.
The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10 3 keV-10 keV.The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region.The importance of rotational coupling for chargetransfer process is stressed.Compared with the radiative charge-transfer process,nonradiative charge transfer is a dominant mechanism at energies above 15 eV.The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail.The radiative and nonradiative charge-transfer rate coefficients from low to high temperature are presented.
The ionization process of B2+ by H+ impact is studied using the continuum-distorted-wave eikonal-initial-state (CDW-EIS) method and the modified free electron peak approximation (M-FEPA), respectively. Total, single-, and double- differential cross sections from 1s and 2s orbitals are presented for the energy range from 10 keV/u to 10 MeV/u. Comparison between the results from the two methods demonstrates that the total and single-differential cross sections for the high-energy incident projectile case can be well evaluated using the simple M-FEPA model. Moreover, the M-FEPA model reproduces the essential features of the binary-encounter (BE) bump in the double-differential cross sections. Thus, the BE ionization mechanism is discussed in detail by adopting the M-FEPA model. In particular, the double- and single-differential cross sections from the 2s orbital show a high-energy hip, which is different from those from the 1s orbital. Based on Ref. [1], the Compton profiles of B2+ for 1s and 2s orbitals are given, and the hips in DDCS and SDCS from the 2s orbital are explained.
Weak- and hyperfine-interaction-induced 1s2s1S0→ 1s2 1S0E1 transition rates for the isoelectronic sequence of Helike ions have been calculated using the multi-configuration Dirac–Hartree–Fock(MCDHF) and relativistic configuration interaction methods. The results should be helpful for the future experimental investigations of parity non-conservation effects.
