Photo-ionization processes of two-electron atoms near the critical nuclear charge

K. V. RODRIGUEZ, G. GASANEO, S. OTRANTO, D. M. MITNIK

Freiburg, Alemania

Conferencia; XXV International Conference on Photonic Electronic and Atomic collisions (ICPEAC); 2007

     In this report we study the Z-dependence of two-electron atoms in the limit in which the nuclear charge tends to its critical value Zc. The latter, is the minimum charge needed to bind the two electrons and is obtained as the zero of the following function: f(Z)=E(Z)+m/2 Z2 where ì is the the reduced mass of the system and E(Z) the state energy.      In the present work we calculate the 1sns wave functions and energies of two-electron ions using the angular correlated Configuration-Interaction method [1,2]: Y=Sn2,n3,n23=1N Sm,n=1M al,m,n(n2,n3,n23) Fl,m,n(n2,n3,n23) The angular correlated Configuration-Interaction  wave functions are given by   F l,m,n(n2,n3,n23)=jn2(Z,r2) jn3(Z,r3) cn3(Z,r3) r2l r3m r23n F l,m,n(n2,n3,n23)=jn2(Z,r2) jn3(Z,r3) cn3(Z,r3) r2l r3m r23n where öni are the hydrogenic bound functions and ÷ is an angular correlation factor.       In  Figure 1 we show how the binding energy of the ground and the first excited states evolve when the nuclear charge moves from 2 to Zc.           During the last decade, the role of the three-body correlations for two-electron atoms have been explored in processes like (e,2e) and (g,2e) for Z³1 [3,4] and their fingerprints established in calculations of cross sections  for single and double ionization by photon and charged particle impact.       In this work, we extend those studies to the Zc limit and study how the enhancement of the interelectronic repulsion compared to the interaction between the electrons and the nucleus modifies the ionization mechanisms, or rules the way in which the emitted electrons leave the reaction region.       Fig.1 Reduced? Binding energy as a function of the nuclear charge for two-electron atoms in the angular correlated CI method.     Acknowledgments   This work has been supported by ANPCYT PICTR 03/00437, CONICET PIPs 5595 and 6268, UNS PGI 24/F038, and UBA UBACyT X075 (Argentina).    References: 1.        L. U. Ancarani and G. Gasaneo, Phys. Rev. A 75,1 (2007)  2.        G. Gasaneo, K. V. Rodriguez and D. M. Mitnik,  Submitted to J. Phys. B. 3.        M. A. Kornberg and J. E. Miraglia PRA (1994). 4.        Stia and Rivarola JPB 2002