Cai Xiao-Hong

K x-ray relative transition probabilities for 39?Z?68

In this paper we report the measurements of the K x-ray relative transition probabilities as follows: K-beta/K-alpha for the atomic numbers Z = 39, 51, 62, 63, 64, 66, 67 and 68; and K-alpha2/k(alpha1), k(beta1)(1)/k(alpha1), k(beta2)(1)/k(beta1)1, and k(beta3)/k(beta2) for the atomic numbers Z = 62, 63, 64, 66, 67 and 68 as induced by protons at an energy of 3 MeV. The experimental results obtained are then compared with relativistic Hartree-Fock calculations.

Studies of K-shell x-ray energy shifts induced by MeV/u heavy ions

This paper reports that the K x-ray spectra of the thin target (47)Ag, (48)Cd, (49)In and (50)Sn were measured by an HPGe semi-conductor detector in collisions with 84.5 MeV (6)C(4+) ions. Our experiment revealed the K alpha x-ray energy shifts were not obvious and the K beta(1) x-ray energy shifts were about 90 similar to 110 eV. The simple model of Burch et al has been previously used to calculate the K x-ray energy shifts due to an additional vacancy in 2p orbit. The present work extends the model of Burch to calculate the x-ray energy shifts of multiple ionized atoms induced by heavy ions with kinetic energy of MeV/u. In addition to our experimental results, many other experimental results are compared with the calculated values by using the model.

The response of Chinese scholars to thequestion of “How did cooperative behavior evolve?”

Cooperation has been observed in several levels of biological organization and among animals and humans. However, in a competitive world, cooperation is a conundrum. In 2005, editors from Science suggested 125 questions facing science for Science ’s 125th anniversary, which include the question of “How Did Cooperative Behavior Evolve?”. From the perspective of Chinese scholars, we summarized the research trends and present research situation in the field of cooperative behavior. Furthermore, we discussed the mechanism of cooperative behavior from a variety of levels, including theories and models, behavioral patterns, neural bases, and molecular genetics. Finally, we briefly introduced the advantages and disadvantages of Chinese scholars in the field of cooperation research, and addressed the future research directions.合作＋行为普遍存在于动物界和人类社会.然而,在激烈的生存斗争中,合作行为的成因是难以被理解的一个谜题.Science在2005年把＂合作行为是如何进化的＂这一问题列为125个科学前沿问题之一.本文从中国学者的角度出发,梳理了国内研究者在合作行为这一领域的研究总体态势及研究现状,进而从理论模型、行为学、神经基础、分子遗传学等角度探讨了合作行为的机制.最后总结并讨论了中国学者在合作领域进行研究所拥有的优势及存在的不足,并对今后的研究进行展望.

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.

Transfer ionization of the isocharge sequence ion and Ar collisions

The ratios of transfer ionization to single capture for isocharge Cq+, Nq+, Oq+, Neq+ ions on Ar atoms are measured by using position-sensitive and time-of-flight techniques. It is found that the ratio R-1 increases with nuclear charge Z in a q=4 sequence, and the ratio R-1 sequences have the minimum values at Z=7 and Z=8 in q=5 and q=6 sequences, respectively, and the ratio R-1 decreases with the increase in the nuclear charge Z in a q=7 sequence. The results may be explained within the frame of the statistical model. It may be concluded that the transfer ionization depends remarkably upon the electronic structure of the projectile. The projectiles used in this study have the same charge state and velocity, but different electronic structures. The dependence of the ratio R-1 on q is studied for Ne9+-Ar collisions. The ratio R-1 is found to increase as q increases for Ne9+-Ar collisions. The measured dependence of the ratio R-1 on q is compared with the calculation using the molecular Coulomb over-barrier model.

Energy Spectra of Sputtering Ions Induced by 209Bi25+, 28+ Ions bombardment on Al and Be

We have experimental investigated sputtering ions of ~MeV 209Bi25+,28+ collision with metal surfaces by 127° electrostatic coaxial cylindrical energy spectrometer, which enabled us to measure energy spectrum fast over energy of sputtering ions from 0 to 3.5 keV. The results show unprecedented details on the reaction dynamics.

Light emission from ion-bombarded aluminum surface

The intensities of the characteristic radiation emitted by the sputtered aluminum atoms and ions are measured as a function of the ions kinetic energy in the wavelength range 300-500nm. For 260-520keV Kr13+ ions bombarded the aluminum surface, the observed spectra show that projectile ion energy has more or less no effect on the excitation of the sputtered species.

Multi-Electron Processes in 4.15–11.08 keV/u13C6+ on Argon Collisions

The relative partial cross sections for 13C6+–Ar collisions at 4.15–11.08 keV/u incident energy are measured. The cross-section ratios σ2E/σSC, σ3E/σSC, σ4E/σSC and σ5E/σSC are approximately the constants of 0.51±0.05, 0.20±0.03, 0.06±0.03 and 0.02±0.01 in this region. The significance of the multi-electron process in highly charged ions (HCIs) with argon collisions is demonstrated (σME/σSC as high as 0.79±0.06). In multi-electron processes, it is shown that transfer ionization is dominant while pure electron capture is weak and negligible. For all reaction channels, the cross-sections are independent of the incident energy in the present energy region, which is in agreement with the static characteristic of classic models, i.e. the molecular Coulomb over-the-barrier model (MCBM), the extended classical over-the-barrier model (ECBM) and the semiempirical scaling laws (SL). The result is compared with these classical models and with our previous work of 13C6+-Ne collisions [Chin. Phys. Lett. 23 (2006) 95].

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.

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.