Same as Fig. 6, but in three separate plots corresponding to the three domains. Top: low-energy levels. Middle: medium-energy levels. Bottom: high-energy levels. Least-squares fits of all available levels are shown as solid straight lines. For the low energy levels, the 0 cm^-1 level corresponding to component 1 is not included in the fit (see text). Limits on the least-squares slope are shown as dashed lines for the low-energy levels, centered over the weighted average of the four excited levels. The population of the low-energy levels follow a Boltzmann distribution, which is consistent with an excitation temperature of about 1300 K.