Residuals of the measured ¹³C¹⁴N wavenumbers (C. Sneden et al. 2014) of A²Π(v_A = 9)–X²Σ⁺(v_X = 3, 4) transitions (see Table 3) from their theoretical counterparts. The black frames highlight the rovibronic transitions locally perturbed by the nearby X²Σ⁺(v_X = 13) levels. The calculated fractional partition of the mutually perturbed A²Π(v_A = 9) and X ²Σ⁺(v_X = 13) rovibronic terms is given in Table 7.