Description

Atomic Li and Li-like ions realize the simplest four-body Coulomb problem, and when all three electrons are excited the system exhibits distinct electron–electron correlation effects. Several experimental [1-3] and theoretical investigations [4-6], aiming at an understanding of this fundamental system, can be found in the literature. Even, quite a few review articles have devoted to have detailed perspective on the system. All these works include H2-, He-, Li atom to Li like Ne. However no studies are available yet on this system in a highly charged ions. Excitation mechanism of such exotic systems is an important aspect. The interactions between highly charged ions and solid surfaces [7] lead to the hollow states like triply excited states are possible to form. Further, multi-electron capture from the surface by highly charged ions increases with its charge state. Hence, beam-foil excitation is a highly efficient technique to produce such exotic systems. Recently in our beam foil experiment, V ion beam of energies 150,100,75MeV on 80μg/cm2, certain transitions originating from short lived states (≪1 ps) of He-like V have been observed at delayed times of ~110-150 ps. In the experiment two peaks, first at 7.56keV and second at 5.46keV energy are observed. Peaks are assigned to decay of 2p2 to 1s2p and 3p2 to 1s2p state. It is concluded that observations of these transitions were possible only if a triply excited, double auto-ionizing metastable state of Li-like V fed the population of highly excited states (short-lived) of He-like V. A triply excited state located energetically above a doubly excited state in the singly charged target ion. Now the decay may occur to such a doubly excited state, which may further decay by autoionization to a state in the doubly charged ion. The first and second transition was concluded to come from 2p3and 3p3 after getting autoionized. Till now the theoretical calculations and the experimental observations of triply excited state have been done only up-to Li-like Ne ions. This is for the first time that transition from doubly excited states realizing triply excited states of Li-like for Z more than 10. References: 1. E. J. Knystautas, J. Phys. B: At. Mol. Opt. Phys. 25, L395 (1992). 2. L.M. Kiernan et al., Phys. Rev. Lett. 72, 2359 (1994). 3. S. Mannervik, Phys. Rev. A 39, 3964 (1989). 4. K. M. Aggarwal, Phys. Scr. 85, 065301 (2012). 5. M. Ahmed, Phys. Rev. A 12, 1176 (1975). 6. N. A. Piangos, Phys. Rev. A 48 4142 (1993). 7. H. P. Winter and F. Aumayr, J. Phys. B: At. Mol. Opt. Phys. 32 R39 (1999).