Liu Yu-Wen

L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions

The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16+ions are measured. The energy of the Ar16+ions ranges from about 150 keV to 350 keV. The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data. The explanation of these experimental results is in the framework of the adiabatic direct-ionization and the binding energy modified BEA approximation. We consider, in the slow asymmetric collisions such as Ar and Mo/Zr, the transient united atoms (UA) are formed during the ion-surface interaction and the direct-ionization is the main mechanism for the inner-shell vacancy production. Generally, the theoretical results are in good agreement with the experimental data.

Single-and-double electron loss of O2+ in collisions with argon and helium

This paper reports that the ratios of double to single electron loss cross-section (R) of O2+ in collision with Ar and He at the velocity of 1–4ν0 (ν0 is the Bohr velocity) have been obtained by the coincidence technique. The trend of R – V in the experiment indicates that the effective charge varies with injected velocity. The effective charge can be obtained by the n-body classical trajectory Monte Carlo method, which is interpreted by the molecular Coulomb over barrier model.

Double Electron Processes in Collisions of Partially Stripped Ions Cq+(q = 1−4) with Helium

The multi-electron processes are investigated for 17.9–120 keV/u C1+, 30–323 keV/u C2+, 120–438 keV/u C3+, 287–480 keV/u C4+ incident on a helium target. The cross-section ratios of double electron (DE) process to the total of the single electron (SE) and the double electron process (i.e. SE+DE), the direct double electron (DDI) to the direct single ionization (DSI) as well as the contributions of DDI to DE and of TI to DE are measured using coincidence techniques. The energy and charge state dependences of the measured cross-section ratios are studied and discussed.

Investigation of transfer ionization in collisions of partially stripped carbon ions with helium at low to intermediate velocities

The ratios of transfer ionization (TI) to single-electron capture (SC) cross sections have been measured for the collisions of partially stripped Cq+ ions (q = 1-4) with He. The collision velocity ranges from 0.7 to 4.4v(0) (v(0) is the Bohr velocity). The projectile-ion and recoil-ion coincidence technique is used to separate the processes of TI and SC. The ratios reach the maximum when the velocity is about 3.7 v(0). This can be explained qualitatively based on the two-step mechanism. The experimental results are also compared with the results calculated using the classical trajectory Monte Carlo (CTMC) method. The CTMC results are in agreement with the experimental data basically. The discrepancies in higher velocity region are interpreted by the effective charge effect.

Production of recoil ions Hei+ accompanied by single electron loss of 0.2–7 MeV Cq+ and 0.25–5 MeV Oq+ (q = 1 – 4) ions

Target ionization accompanied with projectile electron loss is investigated for 0.2–7 MeV Cq+ (q = 1 – 4) with He and 0.25–5 MeV Oq+ (q = 1 – 4) with He collisions. For projectile single-electron loss channel, the He double-to-single ionization ratio R is nearly independent of projectile charge state but dependent on the nuclear charge of projectile Zp. The results are analysed with atomic structure qualitatively. So far there have not existed the experimental data comparable with our results, to our knowledge. The ratio R is interpreted in terms of the two-step mechanism. This analysis agrees well with similar experiments in the literature.

Multiple ionization of argon accompanied by electron loss and capture of 0.22-6.35 MeV C q+ ions

In this paper a projectile ions-recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22–6.35 MeV Cq+ (q = 1 – 4) ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization (or the single capture) of argon associated with single electron loss (or single electron capture) by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.