Here m is the mass of the nucleon, N is the total number of harmonic oscillator quanta in the spherical basis, ℓ ℓ is the orbital angular momentum operator, ℓ ℓ 2 is its square (with eigenvalues ℓ ℓ ( ℓ ℓ + 1 ) ), ⟨ ⟨ ℓ ℓ 2 ⟩ ⟩ N = ( 1 / 2 ) N ( N + 3 ) is the average value of ℓ ℓ 2 over the N shell, and s is the intrinsic spin.