33.5 Operator: adjoint, 6.4; commutator, 6.3; Hermitian, 6.4; linear, 6.1; projection, 8.3; unitary, 7.1 Orbital angular momentum, see Angular momentum Orbitals, atomic, 5.6, 16.2; s, p, d, f, 5.6 Orthogonality, 3.2, 8.3, 9.1 Orthonormal basis, 8.3 Outer product, **8.3**