Portion of the experimental spectrum recorded with the JPL experimental setup in the frequency range 1 138 450−1 138 570 MHz. The simulated spectrum is also provided by using the Hamiltonian parameter values given in Table 2 and the dipole moment components as explained in the text. The involved features are assigned as Γ−J_Ka,Kc for a transition to a state with J′ = J − 1, , and and with symmetry Γ (A or E). Transitions J = K_a + K_c are labeled in blue and J + 1 = K_a + K_c in green.