By use of optical spectrum technology, the spectra of X-ray induced by highly charged 40 Ar q+ ions interacting with Au surface have been studied. The results show that the argon Kα X-ray were emitted from the hollow atoms formed below the surface. There is a process of multi-electron exciting in neutralization of the Ar 16+ ion, with electronic configuration 1s 2 in its ground state below the solid surface. The yield of the projectile Kα X-ray is related to its initial electronic configuration, and the yield of the target X-ray is related to the projectile kinetic energy.Keywords: highly charged ion, hollow, multi-electron excitation, X-ray.When a highly charged ion with many inner shell holes, provided by the electron cyclotron resonance (ECR) ion source, is approaching to a metallic surface, the conducting-band electrons in the metal can resonantly transfer into the high orbits of the projectile with the principal quantum number / n q W ≈ (q is the charge state of the projectile and W the work function of the metal). As the distance of the projectile to the surface is smaller than a critical value of c 2 / , R q W ≈ the potential barrier between the ion and the surface will drop below the Fermi level. In this way, the ion could be temporarily neutralized to form a hollow atom with outer shell occupied and inner shells empty. For example, when Ar 18+ impacts on the Au surface, the hollow argon atom could be formed at R c =33 a.u. with n=20, and when U 92+ impacts on the Au surface, the hollow uranium

Boron compounds are well-known electrophiles. Much less known are their nucleophilic properties. By recognition of the nucleophilicity of the B-H bond, the formation mechanism of octahydrotriborate (BH) was elucidated on the bases of both experimental and computational investigations. Two possible routes from the reaction of BH and THF·BH to BH were proposed, both involving the BH and BH intermediates. The two pathways consist of a set of complicated intermediates, which can convert to each other reversibly at room temperature and can be represented by a reaction circle. Only under reflux can the BH and BH intermediates be converted to BH and BH(H) via a high energy barrier, from which H elimination occurs to yield the BH final product. The formation of BH from THF·BH by nucleophilic substitution of the B-H bond was captured and identified, and the reaction of BH with BH to produce BH was confirmed experimentally. On the bases of the formation mechanisms of BH, we have developed a facile synthetic method for MBH (M = Li and Na) in high yields by directly reacting the corresponding MBH salts with THF·BH. In the new synthetic method for MBH, no electron carriers are needed, allowing convenient preparation of MBH in large scales and paving the way for their wide applications.

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