This must be combined with a spin eigenfunction \(\uparrow \uparrow\), \(\downarrow \downarrow \), \((\uparrow \downarrow + \downarrow \uparrow )\), or \((\uparrow \downarrow − \downarrow \uparrow )\)...This must be combined with a spin eigenfunction \(\uparrow \uparrow\), \(\downarrow \downarrow \), \((\uparrow \downarrow + \downarrow \uparrow )\), or \((\uparrow \downarrow − \downarrow \uparrow )\), where the first arrow represents the spin state \((m_s = \pm 1)\) of the first electron. \[\psi ({\bf r_1},{\bf r_2}, s_1, s_2) = [u^1_{100} ({\bf r_1}) + u^1_{100}({\bf r_2})][u^2_{100}({\bf r_1}) + u^2_{100}({\bf r_2})] [\uparrow \downarrow − \downarrow \uparrow] \nonumber\]
