Ultraviolet laser spectroscopy of jet-cooled CaNC and SrNC free radicals:Observation of bent excited electronic states

摘要

New electronic transitions of the CaNC and SrNC free radicals ha e been identified in the near ultraviolet. For CaNC one new system, labeled the D-X transition, was observed in the 31 500-33 400 cm~(-1) region. Two new transitions were found for SrNC, the D-X and E-X systems spaning 29100-3100 and 32750-34000 cm~(-1), respectively.Jet-cooled laser excitation spectra yield complex vibrational stru ture, much of which i attributed to excitation of the bending vibration. This has been used to infer that the molecule aopts a nonlinear equilibrium geometryi in the upper electronic state in all three band systems, in contrast to the linear ground electronic state. This structural change is accounted for by the increased diffuseness of the unpaired electron in the xcited states, whihc favors deviation from linearity. All three new excited states are assigned ~2A~' symmetry and correlate with ~2#MIGMA#~+ states in the linear molecule limit. Tentative estimates for the barriers to linearity in the D~2A~' states of CaNC and SrNC have been determined as approx700 and approx1050 cm~(-1), respectively