Charge transfer between Si3+ and helium at thermal and low energies

Rate Coefficient Determination in Charge Transfer Reactions

“…These potential energy curves are in satisfactory agreement with the spin-coupled valence bond calculations of Clarke and Cooper [44]. From these molecular data, a quantum mechanical collisional treatment taking account simultaneously of all the levels involved in the process has been performed [1] and the rate coefficients are displayed in Fig. 6.…”

“…Furthermore, it is important to ask if the measurement of Fang and Kwong obtained using an ion trap with cylindrical symmetry can be compared with a calculation based on the use of a Maxwell-Boltzmann distribution. On the other hand, the calculated rate coefficients [1] from the excited Si 3+ (3p) entry channel appear to be of the same order of magnitude than experimental data points for both T i and T equiv . This could suggest, as already pointed out for the O 2+ ions, that the [2] (broken curves) and Landau-Zener approach, Butler et al [24] (dotted curve) with ion trap experiment at T i and T equiv [14].…”

“…Line intensities provide important information on the electron temperature, density and spatial distributions in the emitting region of the plasma. In some cases, however, the electron may be captured directly in a ground state of the ion, whereupon ionization may occur rapidly via the inverse charge transfer process [1,2]. A precise understanding of charge transfer processes is thus essential for the determination of the ion abundances and ionization balance of the plasmas.…”

“…The potential energy curves have been calculated [1] by means of ab-initio configuration interaction methods based on the CIPSI algorithm with Gaussian basis sets constructed from McLean and Chan-dler [42]. A non-local pseudo-potential [43] has been used to represent the core electrons of the Si atom.…”

Calculation of Rate Coefficients for Electron Capture in Collisions of O2+and N2+Ions with H

“…Rate coefficients for charge transfer between multiply charged ions and He have been measured in ion traps ( Fang & Kwong 1997, and references therein), but EC rate coefficients employed in astrophysics are usually obtained theoretically. In particular, the rate coefficients for ion-H charge transfer reactions tabulated by Kingdon & Ferland (1996) were generally obtained by applying the Landau-Zener formula, although a few of them (Forster et al 1991;Honvault et al 1995;Herrero et al 1995) were calculated by employing ab initio techniques to evaluate the potential energy curves and nonadiabatic couplings. The data of Kingdon & Ferland (1996) are currently included in the CLOUDY program ( Ferland et al 1998), which is widely employed for modeling astrophysical plasmas.…”