The Mg-NC stretching vibronic bands of the MgNC A˜2Π-X˜2Σ+ transition

We have generated MgNC in supersonic free jet expansions, and measured the laser induced fluorescence excitation spectra of the Mg-NC stretching vibronic bands of the A˜2Π-X˜2Σ+ transition. In addition to the bands reported previously, the 302 and 303 bands were found, and the vibronic levels, (0, 0, 2) and (0, 0, 3), in the Ã2Π state were characterized through rotational analysis. Sorting out the spin-orbit constants, ASO′, of the vibronic levels with respect to the two stretching modes, Mg-NC and C-N, we found the opposite dependence of ASO′ upon the two vibrational modes, i.e., ASO′ increases with the excitation of the Mg-NC stretching vibrational mode, while it decreases with the excitation of the C-N mode. These findings were interpreted by an attempt to calculate the dependence of ASO′ upon the geometry along the vibrational normal modes.