Fig. 6-2.  A contour map of the electron density distribution (or the molecular charge distribution) for H₂ in a plane containing the nuclei. Also shown is a profile of the density distribution along the internuclear axis. The internuclear separation is 1.4 au. The values of the contours increase in magnitude from the outermost one inwards towards the nuclei. The values of the contours in this and all succeeding diagrams are given in au; 1 au = e/a_o³ = 6.749 e/ų.