Figure 3. Redistribution of the electron density visualised as the charge density difference between the positively charged excited state and the neutral ground state of EMImBF4. The green isosurface value equals −0.05 a.u. (an increase of the electronic density). The red isosurface value equals 0.05 a.u. (decrease of the electronic density). Superscripts provide the IUPAC atom numbering. Circled numbers indicate atoms by the data shown in Figure 4 and Tables 1–2.