An analysis of the A 2Π–X 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 rs-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.