The confined helium atom; an Informational approach
In this work we study the helium atom confined in a spherical impenetrable cavity by using informational entropies. We use the variational method to obtain the energies and wave functions of the confined helium atom as a function of the cavity radius $r_0$. As trial wave functions we use one uncorrelated function and four functions with different degrees of electronic correlation. We computed the Shannon entropy, Fisher information, Kullback--Leibler entropy, Disequilibrium, Tsallis entropy and Fisher--Shannon complexity, as a function of the box radius $r_0$. We found that these entropic measures are sensitive to electronic correlation and can be used to measure it. These entropic measures are less sensitive to electron correlation in the strong confinement regime ($r_0<1$ a.u.).