D. Excitation Beyond the LUMO. Each of the methods discussed so far can be extended to transitions into virtual orbitals above the LUMO, but such calculations often suffer variational collapse or other SCF convergence issues. Using the LUMO to stand in for the transition potential generated by the higher-lying virtual orbitals is a way to sidestep this problem, and an especially promising protocol is XCHM, for which the final state is charge-neutral. Excitation energies for XCHM are computed according to