It can be seen from Table that for the studied carbon chains, the trends of 1 Σ u + ← X 1 Σ g + wavelength obtained by two theoretical methods are consistent, with a systematic deviation between them of 14.3 ± 1.0 nm. The calculated values of 1 Σ u + ← X 1 Σ g + wavelengths at the TD-ωB97XD/def2-TZVP level are in surprising agreement with all experimental observations. Specifically, the simulated wavelengths appear to be systematically underestimated by only 5.6 ± 1.8 nm relative to the experimental values. Such consistency confirms the reliability of our computational strategy and ensures the accuracy of all subsequent characteristics analyses.