Cross Sections For Double Charge Transfer Research Articles

A Time-Dependent-Density-Functional-Theory Study of Charge Transfer Processes of Li2+ Colliding with Ar in the MeV Region

We study charge transfer of a multi-electron collision system Li2+ + Ar using the time-dependent density functional theory non-adiabatically coupled to the molecular dynamics. By implementing the particle number projection method, the single- and double-charge transfer cross sections are extracted at MeV energies, which are in good agreement with the experimental data available. The analysis of charge transfer probabilities shows that for energies higher than 1.0 MeV, the single-charge transfer occurs for a broader range of impact parameters, while the double-charge transfer is dominated by close collisions. To gain the population of captured electrons on the projectile, we compute the orbital projection probabilities. It is found that the electrons of the Ar atom will most possibly transfer to the 2p orbitals of the Li2+, and only a small portion of captured electrons distribute on the s orbitals. This work verifies the capability of the present methodology in dealing with charge transfer in dressed ion collisions at MeV energies.

Single and double charge transfer in the Ne2++He collision within time-dependent density-functional theory

We calculate the charge-transfer cross sections for the ${\mathrm{Ne}}^{2+}+\text{He}$ collision. To this end, we employ Ehrenfest molecular dynamics with time-dependent density-functional theory. The active electrons of the projectile are handled by applying an initial velocity to the Kohn-Sham orbitals via a Galilean boost. The dynamical calculations are performed in an inverse collision framework---the reference frame considers ${\mathrm{Ne}}^{2+}$ to be initially at rest, which ensures numerically converged final-time scattering states. The charge-transfer probabilities are extracted by extending the particle number projection technique to be able to handle the degenerate ${\mathrm{Ne}}^{2+}$ ion. Compared with experimental data available at 10--3000 keV, a fairly good agreement is found for the calculated single- and double-charge transfer cross sections, superior to other theoretical calculations for this ${\mathrm{Ne}}^{2+}+\text{He}$ collision. A time-resolved analysis of the charge-transfer probabilities finds that ionization to the continuum also takes place after the charge transfer has occurred. To account for it, the final scattering states should be followed for a long time, approximately 350 fs, until they stabilize.

Double charge transfer cross sections in collision of protons with helium atom

Theoretical total cross sections for the double charge transfer in proton-helium collisions are analysed using the four-body boundary corrected continuum intermediate state approximation in the energy range of 30 to 500 keV. We have also obtained differential double capture cross sections as a functions of projectile scattering angle. The intermediate continuum state of each of the active electron has been taken into account in this formalism. Our calculated results are compared with the previous experimental and theoretical values. The agreement is very encouraging.

Absolute charge transfer and fragmentation cross sections in He2++C60 collisions

We present a set of theoretical methods to study the different processes taking place in ion-fullerene collisions. In particular, we focus on charge transfer, excitation and fragmentation processes. These methods have been successfully applied to the case of He2+ + C60 collisions. We have found that single and double charge transfer cross sections are of the same order of magnitude in the velocity range studied (impact energy ∼ 0.1 – 10 keV). Fragmentation of C+60 into C+58 + C2 is observed only with large excitation energies and/or if one waits long enough (detecting the fragments at large distances from the collision). The agreement between our predictions and the experimental results supports the validity of the methods presented.

Charge Transfer Cross Sections of3He2+Ions in Collisions with He Atoms and H2Molecules in the Energy Range of 1∼10 keV

The single- and double-charge transfer cross sections of 3 He 2+ ions have been measured for targets of He atoms and H 2 molecules in the energy range from 1 to 10 keV by using a microchannel plate-position sensitive detector. The present results are compared with those from other experiments and with available theoretical calculations.

A study of core effects in quasimolecular structure

In previous work we have studied the effect on an “inert” core in atomic collisions, for the usual case where the corresponding “isoelectronic” (same number of active electrons) quasimolecules have similar correlation diagrams, and collisional mechanisms are similar. Here these studies were extended to cases where the correlation diagrams, and thereby the reaction mechanisms, are qualitatively different. In particular, the effect of the inner CHe 6+ core on the correlation diagram of the CHe 4+ quasimolecule, and on the mechanisms of C 4+ + He single and double charge transfer cross-sections were analysed, as compared with Be 4+ + He, where the core is empty. The analysis was made in the light of the analogy between the treatment of doubly excited and two-valence electron states. The absence of core effects at high nuclear velocities is discussed.