Ground- and excited-states reactivity dynamics of hydrogen and helium atoms

Dynamic profiles of various reactivity parameters like hardness, chemical potential, polarizability, phase volume, and electrophilicity index are studied in gaining insights into the ground- (n = 1) and excited- (n = 15) states dynamics of hydrogen and helium atoms. Pertinent time-dependent Schrodinger equations are solved for the ground and excited states of hydrogen atom and the Rydberg state of the helium atom while a generalized nonlinear Schrodinger equation is solved for the ground state of the helium atom, all interacting with external electric fields of different frequencies and intensities. For both the atoms ground states are more stable than the corresponding excited states. Hardness and phase volume can be used as diagnostics for the chaotic ionization from the Rydberg states of those atoms. Other quantities like higher-order harmonics also lend additional support. Dynamic variants of the maximum hardness and minimum polarizability principles are found to be operative. (C) 2002 Wiley Periodicals, Inc.