We now consider the ground 5 2 S and 5 The energy shift for the ground state is predicted to decrease, slightly, and then to remain stationary. The transition energies (Figure (c)) echo the preceding plot and show that the two excited states with a p-type orbital orthogonal to the field (the coordinate to the ethene molecule) are stabilised whereas the third excited state is destabilised. For the energy shifts and the transition energies, the shifts when the E is applied is greater for 87 Rb with ethene than for 87 Rb with ethane, with the exception of the energy shift and transition energy for the third excited state which undergoes a larger blue-shift in the presence of ethane.