meV and thus requires an additional phonon, 𝑛 c = 7, in order to overcome the reference barrier, corresponding to an energy of 𝐸 A ( 7 Li)= 0.230 eV. The corresponding Δ𝐸 A = (0.230 -0.213) = 0.017 eV agrees with the result of Eq. 5. Note that this example was chosen to illustrate the concept using a single harmonic oscillator, where phonon occupation must be integer values. Since Eq. 5