An analysis of the à ²Π-X̃ ²Σ ⁺ band system of isotopically substituted calcium isocyanide CaNC

The strong visible band systems of a supersonic molecular beam sample of isotopically substituted CaNC (¹³C and ¹⁵N individually) have been recorded at high resolution by laser-induced fluorescence spectroscopy. The spectra have the general appearance of the expected à ²Π-X̃ ²Σ⁺ band systems, but the energy levels of both the |Ω|=1/2 and 3/2 excited substates have localized perturbations. Spectroscopic parameters for the X̃ ²Σ ⁺ state of the isotopomers were extracted from a least-squares fit to the appropriate combinations differences of the observed transitions frequencies. Excited state effective parameters were extracted by directly fitting the unperturbed portions of the optical spectra. The r _s-structure bond lengths for the ground electronic state were determined to be Ca-N=2.2065(58) Å and N-C=1.1186(58) Å. The permanent electric dipole moments for the Ca¹⁵NC isotopomer were determined to be 5.93(8) and 6.69(9) D for the à ²Π and X̃ ²Σ⁺ states, respectively.