Quantum fluid density functional theory of chemical reactivity in a two-state ensemble

A quantum fluid density functional approach is adopted in monitoring the dy namics of various global and local reactivity parameters of a helium atom i n a two-state equiensemble, having an interaction with an external laser fi eld as well as an incoming proton. The effect of an increase in the excited -state contribution in a two-state ensemble is more pronounced in global re activity parameters than the local ones. Global reactivity indices are foun d to be more sensitive to the external perturbation, for the whole time-dep endent process, than the local indices. Most of the local quantities show d rastic changes only at the beginning of the processes. In the atom-field in teraction problem, electronegativity, polarizability and entropy oscillate with the field and hardness attains a steady value after the initial transi ents die out. The ion-atom collision process can be divided into three dist inct regimes in terms of the time-dependent electronegativity profile. In t he encounter regime, hardness and entropy maximize and polarizability minim izes. Dynamical variants of the principles of maximum hardness, maximum ent ropy and minimum polarizability are shown to be operative. (C) 2000 Elsevie r Science B.V. All rights reserved.