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The collision-induced dissociation (CID), electron capture (EC), and dissociative capture (DC) processes in H2+ + He collision are investigated by the quantum-mechanical molecular-orbital close-coupling method in the energy range of 0.02-10 keV/u. The studies are based on the ab initio calculation of the molecular structure data for different H2+ alignments with respect to the incident beam direction. The cross sections are compared with the available experimental and theoretical results. The CID process dominates the EC and DC processes. The CID cross sections sensitively depend on the molecular orientations at the time of dissociation in the energy region considered. Dissociation is found to be more likely to occur when the molecular axis is aligned perpendicular to the collision trajectory. The rotational couplings play an important role in dissociation processes. [ABSTRACT FROM AUTHOR]

The x-ray spectra resulting from single-electron capture in charge-exchange collisions of Nel0+ with He and Ne atoms are investigated for the projectile energy of 4.54 keV/u using the two-center atomic-orbital close-coupling method. The calculated spectra of the Ne9+ ion produced in Ne10+ + He and Nel0+ + Ne election-capture collisions have, generally speaking, the same level of agreement with experimental measurements as those calculated previously by the classical trajectory Monte Carlo method, indicating that multi-electron-capture processes, particularly in the case of the Nel0+ 4- Ne system, significantly affect the considered spectra. The effects of two-electron capture on the spectral line intensity have been demonstrated qualitatively by using the binomial statistics and independent particle model for the target outer-shell electrons. The role of multi-electron-capture processes in the Nel0+ 4- Ne collision system needs further attention. [ABSTRACT FROM AUTHOR]

The nonradiative charge-transfer processes for the Be3+(ls) + H(Is) collisions are investigated by the quantummechanical molecular orbital close-coupling" method in the energy range of 0.01-10 keV/u. The radiative charge-transfer cross sections are calculated by the optical potential and semiclassical methods in the energy range 10-6--10³ eV/u. The needed molecular data are obtained by the ab initio multireference single- and double-excitation configuration interaction method. Total and state-selective cross sections are presented and compared with other available theoretical data. Our calculation agrees well with the atomic orbital close-coupling results of Liu et al. [L. Liu, D. Jakimovski, J. G. Wang, and R. K. Janev, J. Phys. B 43, 144005 (2010)], but there exist some discrepancies with the semiclassical molecular orbital close-coupling results of Shimakura [N. Shimakura, J. Phys. B 21, 2485 (1988)]. The present results show that the capture to Si2+(1s3l) states is dominant in the whole energy range with the exception of a narrow range of 2-4 keV/u. Rotational couplings play an important role not only in the state-selective cross sections, but also in the total charge-transfer results. At energies below 40 eV/u, the radiative charge transfer exceeds the nonradiative process. [ABSTRACT FROM AUTHOR]

Single-electron capture (SEC) and double-electron capture (DEC) processes in collisions of ground state N3+ (2s² ¹S) ions with He are investigated by using the quantum-mechanical molecular-orbital close-coupling (QMOCC) method. The ab initio adiabatic potentials, radial and rotational coupling matrices utilized in QMOCC calculations, are obtained from the multireference single- and double-excitation configuration interaction approach. Total and state-selective SEC and DEC cross sections are presented in the low-energy range from 0.1 eV to 15 keV (i.e., 0.007 eV/u -1.07 keV/u) and rate coefficients in the temperature range from 104 to 107 K. Our results indicate that the SEC dominates the charge-transfer process in the considered energy region of this collision system and the SEC cross sections are nearly constant in the relatively high-collision energy region, while the DEC cross sections are about 2 orders of magnitude smaller. It is found that, for the SEC processes, in the dominant mechanisms, electrons are captured to exoergic channels N2+ (2s2p² ²D, ²S), and for the DEC processes, they are captured to N+ (2s²2p² ¹D, ¹S). Our calculations also reveal that rotational couplings become important at E > 10 eV/u for SEC and E > 200 eV/u for DEC processes. [ABSTRACT FROM AUTHOR]

Polarization spectroscopy of He+(nl) ion produced in He2+-H(1s) collisions in a Debye plasma is studied by the two-center atomic orbital close-coupling (TC-AOCC) method in the energy range 1-200 keV/u. The atomic orbitals and electron binding energies of atomic states are calculated within the Debye-Hückel approximation of the screened Coulomb potential and used in the AOCC dynamics formalism to calculate the magnetic substate-selective electron-capture cross sections. It is demonstrated that the screening of Coulomb interactions affects the entire collision dynamics and the magnitude and energy behavior of m-state-selective cross sections. The changes in magnetic substate-selective electron-capture cross sections when the interaction screening varies introduce dramatic changes in the polarization spectroscopy with respect to the unscreened interaction case. The magnetic substate-selective electron-capture cross sections, as well as the polarization degrees for the 2p 2P3/2-1s 2S1/2,3p 2P3/2-2s 2S1/2,3d 2D5/2-2p 2P3/2, and 3d 2D3/2-2p 2P1/2 transitions in the He+ ion produced in this collision system, are presented and discussed for a number of representative screening parameter values. [ABSTRACT FROM AUTHOR]

The electron capture process for the Si3+(3s) + H(ls) collisions is investigated by the quantum-mechanical molecular orbital close-coupling (MOCC) method and by the two-center atomic orbital close-coupling (AOCC) method in the energy range of 10-5-10 keV/u and 0.8-200 keV/u, respectively. Total and state-selective cross sections are presented and compared with the available theoretical and experimental results. The present MOCC and AOCC results agree well with the experimental measurements, but show some discrepancy with the calculations of Wang et al. [Phys. Rev. A 74, 052709 (2006)] at E > 40 eV/u because of the inclusion of rotational couplings, which play important roles in the electron capture process. At lower energies, the present results are about three to five times smaller than those of Wang et al. due to the difference in the molecular data at large internuclear distances. The energy behaviors of the electron capture cross sections are discussed on the basis of identified reaction mechanisms. [ABSTRACT FROM AUTHOR]

State-selective and total single-electron-capture cross sections in collisions of H+ with the excited Li*(2p) atom have been investigated by using the full quantum-mechanical molecular orbital close-coupling (QMOCC) method in the energy range 0.001-3 keV/u and by the two-center atomic orbital close-coupling (TC-AOCC) method in the energy range 0.1-100 keV/u. The present results are also compared with data from other sources when available. It is found that the total and partial electron-capture cross sections are sensitive to the initial p-state charge cloud alignment, particularly in the low-energy region. [ABSTRACT FROM AUTHOR]

The nonradiative charge-transfer processes of Li++Na(3s) collisions have been investigated by using the fully quantum-mechanical molecular-orbital close-coupling method and the two-center atomic-orbital close-coupling method for the energy range of 10-4-2keV/u and 0.2-10keV/u, respectively. The radiative charge-transfer, radiative decay, and radiative-association processes have been studied by employing the fully quantum, optical-potential, and semiclassical methods for the energy range of 2×10-10-110eV/u. The nonradiative charge-transfer processes dominate the collisions for energies above 0.2 eV/u while radiative decay processes dominate in the lower-energy region. Especially, we found that the radiative-association process is more important than the radiative charge-transfer process when E<2×10-2eV/u. The rate coefficients of nonradiative and radiative processes are also given for the temperature range of 3×104-2×109K and 10-6-10³K, respectively. [ABSTRACT FROM AUTHOR]

The radiative association processes for Na+ colliding with 87Rb(5s) atoms have been investigated by using the quantum-mechanical method. The total and partial cross sections that associate to the specific rovibrational states are calculated rigorously in the energy range of 10-13 - 1.2 × 10-2eV. The association cross sections display rich resonance structures. The ratios of rotationally resolved cross sections to total association cross sections and the ratios of vibrationally resolved cross sections to rotationally resolved cross sections are calculated and presented. For energies less than 10-9eV, association to X²Σ+ (J = 1) dominates over all other association states. As the energy increases, each resonance of the total cross sections is associated with the given angular component of specific bound states. In the energy range of 10-13-1.2×10-3eV, the vibrational states ν = 27 and ν = 28 are the most probable final states. The probability for the formation of molecular ion NaRb+ in the rovibrational states is discussed. The existence of Cooper minima in the radiative association cross sections is found and illustrated. [ABSTRACT FROM AUTHOR]

The time-dependent density functional theory is applied to investigate the charge transfer and electron-loss processes during He2+-Ar collisions in the energy range of 4-300 keV/amu. A coordinate space translation technique is employed to focus our investigation on some certain space of interest such as the regions around the projectile or target. It is shown that both charge transfer and electron-loss processes are important in the considered energy range. One-electron-capture processes dominate charge transfer with the cross sections one to two orders of magnitude larger than two-electron-capture cross sections. The ionization cross sections decrease with increasing the number of ionized electrons. The calculated cross sections are in excellent agreement with available experimental and theoretical results. Evolution of electron density is also presented to explore interactions between the electrons as well as the correlation between the projectile and target during the collisions. [ABSTRACT FROM AUTHOR]

Theoretical calculations have been made for the dielectronic recombination (DR) rate coefficients of Sn12+ ion using a relativistic flexible atomic code with configuration interaction. Comparison of the rate coefficients for 4s, 4p, and 4d subshell excitation shows that while the 4p subshell excitation dominates over the whole temperature region, 4d subshell excitation at low temperature and 4s subshell excitation at high temperature cannot be neglected. In order to facilitate simple applications, the calculated DR rate coefficients are fitted to an empirical formula. The total DR rate coefficient is greater than either the radiative recombination or three-body recombination coefficients for electron temperatures greater than 1 eV. Therefore, DR can strongly influence the ionization balance of laser-produced tin plasmas. [ABSTRACT FROM AUTHOR]

Electron emission from the single-electron capture with simultaneous single ionization in 30 keV/u He2+ on argon was investigated using a reaction microscope, providing the electron energy spectra and momentum distributions. Intensive peaks for electrons with near-zero kinetic energies have been observed. It is demonstrated that mechanisms contributing to the electron emission include direct transfer ionization (DTI), double-electron capture with autoionization (DECA), and single-electron capture with autoionization (SECA) of target. Comparison of resonance energies shows that Ar+ ions in SECA decay mainly through the 3s3p53d states by emitting Auger electrons, and He** in DECA decay through the 2l2l′ states. The dependence of electron emission on the transverse momentum exchange has been studied. In the transfer ionization channel studied here, the DTI process dominates the electron emission, and no saddle point electron mechanism has been found. [ABSTRACT FROM AUTHOR]

The electron transfer mechanism was investigated for the single-electron-capture process in 3-keV/u ArAr8+ -He collisions with cold target recoil ion momentum spectroscopy. The different state-selective electron capture processes were identified for one 1 s electron of He capture into 4 s, 4 p, 4 d - 4 f, and 5 s - 5 p states of ArAr8+. We observed that 1 s to 4 s capture mainly happens at small transverse recoil ion momentum, while 1 s to 4 p capture mainly happens at large transverse recoil ion momentum. By comparing the measured projectile scattering angle distributions to the theoretical calculations, it is suggested that 1 s to 4 s and 1 s to 4 p state-selective capture processes are mainly caused by radial and rotational coupling effects, respectively, and the 4 p ± 1 quantum states are preferred. [ABSTRACT FROM AUTHOR]