Production of Doubly and Triply Excited States by Triple Electron Capture

2. Production of Doubly and Triply Excited States by Triple Electron Capture M. Zamkov, E.P. Benis, P. Richard, T.J.M Zouros,

3. Fundamental problem of a many-body dynamic system – test of the most advanced atomic models Importance in high temperature plasma studies, astrophysics and laser technology Triple electron capture in ion-atom collisions Previous experimental studies V< < 1 a.u. - only • Projectile charge-change • Total charge transfer • Auger spectroscopy in coincidence with recoil ions • TOF Triple coincidence of recoil projectile and target ions with Auger electrons

4. Target ATOM Bare ION Slow Electron dynamics in slow ion-atom collisions V< < 1 a.u. In slow collisions target electrons molecularize – Extended Overbarrier Model.

5. V V> u u V u Triple electron capture in FAST ion-atom collisions Collision time is small! The captured target electrons see H-like levels of the projectile e-e correlations are reduced Independent Particle Model is expected to reproduce triple electron capture in fast collisions

6. Experiment Independent particle model Single electron transfer probabilities were calculated using the close-coupling method Triple electron capture to KLL states in fast C6+ on Ar collisions C6+ + Ar = C3+(1s2l2l’) + Arq+

7. Comparison Independent particle model gives an adequate representation of triple electron capture at high collision velocities v >> 1 Electron correlation effects do not play a significant role in triple electron capture at high collision velocities M. Zamkov, E.P. Benis, T.J.M Zouros, P. Richard, and T.J. Lee, Phys. Rev. A,66, 042714 (2002)

8. Experiment Theory Synchrotron radiation Advanced light source, Berkly Photon factory, Japan Saddle-point complex-rotation R-matrix Dirac-Fock Truncated-diagonalization Configuration Interaction (CI) 1s22s 2Se2s22p2Po 1s22p 2Po2s2p22Se, 2Pe, 2De Visualization of triply excited states using a hyperspherical approach 2p 2s hv 1s Triply excited states Fundamental case of an ideal many-body Coulomb system dominated by electron correlation effects

9. Limitations of Synchrotron radiation Population of resonances only in Li atoms theoretical advances in studying triply excited states for Li-like ions S=3/2 states cannot be reached due to the dipole selection rules Population of the triply excited states by triple electron capture !

10. FAST Ion-atom collisions to populate lower intrashells (n=2) F9+ Ar Ar IPM - free of e-e correlations L shell 2p3 4So 2Po 2Do Concentrating on e-e correlations in decay dynamics 2s2p2 2Se 2Pe 2De 4Pe 1s2s 1P Population of all states ! 2s22p 2Po 1s2s 3P 1s2s 1S 1s2s 3S

11. 2p3 2Po 2Do 2s2p2 2Se 2Pe 2De 4Pe 5 a,b,c 4 (a,b) 2 7 3 8 1s2s 1P 1 (a,b) 1s2s 3P 1s2s 1S 1s2s 3S 6 Auger electron energy (eV)

12. 2s2p2 2D 1s2s 3S 1s2 1S Determination of Autoionization Rates Determination of Branching ratios from channels unresolved In the other technique Resonant Transfer Excitation K vacancy production

13. R-matrix calculation

14. Conclusions • a) First Experimental measurements of absolute cross sections for triple electron capture resulting from fast collisions of bare C on Ar • Extension of the Independent Particle Model (IPM) for the calculation of triple electron capture cross sections. • c) Understanding the role of e-e correlations and projectile screening in triple electron capture resulting from fast ion-atom collisions. • Measurements of absolute differential cross sections, resonance energies and Auger decay branching ratios for all autoionizing triply excited states of fluorine with 2s2p2, 2p3 electron configurations. • b) Independent particle model calculations of the differential cross sections for the formation of triply excited states by triple electron capture