Xu

Reanalysis of the astrophysical S(E) factors of the 6Li(d,α)4He, 7Li(p,α)4He and 6Li(p,α)3He reactions

The experimental data of the Li-6(d,alpha)He-4, Li-7(p,alpha)He-4 and Li-6(p,alpha)He-3 reactions obtained by other groups are reanalyzed in this work to extract their respective astrophysical S(E) factors and the screening energies provided by different environments (LiF solid targets and molecular H-2 or D-2 gas targets). Different from previous authors who investigated these three reactions independently, we study them simultaneously, based on the hypothesis that the screening effects are independent of the isotopic effects and the fact that the screening effects depend on the environments. The present extracted astrophysical S(E) factors result in S-bare(0) = 20.5 +/- 0.5, 0.0616 +/- 0.0017 and 3.63 +/- 0.13 MeV b for the Li-6(d,alpha)He-4, Li-7(p,alpha)He-4 and Li-6(p,alpha)He-3 reactions, respectively. The screening energies are 310 +/- 109 and 218 +/- 38 eV for the LiF solid targets and molecular H-2 or D-2 gas targets, respectively. These deduced screening energies are smaller than that observed by Engstler et al, and the value of U-s = 218 +/- 38 eV for the molecular H-2 or D-2 gas targets coincides with the value of 186 eV estimated from the adiabatic limit, while the value of U-s = 310 +/- 109 eV for the LiF solid targets is still slightly larger than that estimated from theoretical predictions.

X-Ray Emission from Zr, Mo, In and Pb Targets Bombarded by Slow Highly Charged Arq+(q = 13,14,15,16) Ions

We study the L x-ray emission from Zr, Mo and In targets and M x-ray emission from Pb target under bombardment of low energy Arq+ (q = 13,14,15,16) ions. The relative x-ray yields were measured in the projectile kinetic energy range 210-360 keV. It is found that the relative x-ray yields from Zr, Mo and Pb targets increase with the increasing projectile kinetic energy for Ar14+ and Ar16+ projectiles and depend on the potential energy of the projectile remarkably.

Multi-Electron Processes in 13C6+ Ions with Neon Collisions in Energy Region 4.15–11.08 keV/u

The cross-section ratios of double-, triple-, quadruple-, and the total multi-electron processes to the single electron capture process (σDE/σSC, σTE/σSC, σQE/σSC and σME/σSC) as well as the relative ratios among reaction channels in double-electron active, triple-electron active and quadruple-electron active are measured in 13C6+–Ne collision in the energy region of 4.15–11.08 keV/u by employing position-sensitive and time-of-flight coincident techniques. It is determined that the cross-section ratios σDE/σSC, σTE/σSC, σQE/σSC and σME/σSC are approximately the constants of 0.20±0.03, 0.16±0.04, 0.06±0.02 and 0.42±0.05. These values are obviously smaller than the predictions of the molecular Coulomb over-the-barrier model (MCBM) [J. Phys. B 23 (1990) 4293], the extended classical over-the-barrier model (ECBM) [J. Phys. B 19 (1986) 2925] and the semiempirical scaling laws (SL) [Phys. Rev. A 54 (1996) 4127]. However, the relative ratios among partial processes of DE, TE and QE are found to depend on collision energy, which suggests that the collision dynamics depends on the collision velocity. The limitation of velocity-independent character of ECBM, MCBM and SL is undoubtedly shown.

Double electron processes in low energy isotope bare ions C-13(6+) with helium collisions

The isotopic bare ion C-13(6+) was employed to collide with helium at 4.15-11.08ke V/u. The relative partial cross sections were measured by position-sensitive and time-of-flight coincident techniques. It is shown that the direct-ionization (DI) process can be completely ignored in this region, the transfer ionization (TI) process is the most important double-electron channel, and the probability of the pure double-electron capture (DC) process is quite small. The cross-section ratio of the total double-electron (DE) process (i.e. DC+TI) to the single-electron capture (SC) process is experimentally determined to be approximately a constant of 0.09 +/- 0.03 in this region, and this value is obviously smaller than the predictions of the classical over-barrier models and the semi-empirical scaling laws. It is found that; the cross-section ratio of pure DC to DE decreases obviously as the projectile velocity increases. Because the pure DC process only comes from the radiation de-excitation following the DC process and are competed by the TI process (comes from the auto-ionization following the DC process), this implies that the population of the two captured electrons depends distinctly on the collision velocity Comparison with works on Ar16+-He by Wu et al. [Phys. Rev. A 48 (1993) 3617] reveals that the strong projectile-dependent character of the pure DC process exists.