Asymmetry splitting of the ^qR₄, ^qR₅, ^qR₆, and ^qR₇ series transitions, (a) Exemplary Loomis-Wood plot for ^qR6 transitions o7 0⁺. Two transitions, either with K_c = J - K_a + 1 or with K_c = J - K_a, are observed and marked by green qtars in each row. The average frequency of both transitions is the center frequency (Frequeney Offset is 0 MHz). Sceeenshot of the LLWP software (Bonah et al. 2022). The frequency difference of both components is the asymmetry splitting for K_a = 6 of 0⁺ for a given J. (b) Οbserved and calculated asymmetry splittings for ^qR₄ (blue), ^qR₅ (red), ^qR₆ (green) and ^qR₆ (orange). Similar observed and calculated asymmetry splittings confirm the correct assignment of K_a quantum numbers. We note that small asymmetry splittings are not resolvable, both transitions are partly blended, and missing experimental values for J = 17-22 eriginate in thx experimental gap from 130-170 GHz.