Laser spectroscopy of YbO: Observation and analysis of some 0 +- 1Σ + transitions

Abstract

Argon ion and tunable dye lasers have been used to excite different transitions in YbO. Resolved fluorescence spectra have resulted in the observation of three low lying states. Long progressions were observed in the lowest state and vibrational constants have been calculated. High resolution excitation spectra of three bands in the rhodamine 6G region have been obtained and their rotational and isotopic structure (Yb has six isotopes) analyzed. The three bands are all shown to be 0 +- 1Σ + transitions where the 1Σ + state is the lowest observed state of the molecule. Term energies and rotational constants have been determined for each state and the vibrational spacing ΔG 1 2 of the lower state has been calculated. For each state, the isotopic change in constants has been discussed and compared with theory. The isotope effect has been used to determine the vibrational numbering of the upper states and to estimate their vibrational constants. The ligand field theoretical (LFT) model for rare earth oxides is outlined and its predictions for YbO are discussed. The assignment and vibrational frequency of the lowest state are shown to be in accord with the LFT predictions. The principal constants (in cm −1) determined for 174YbO are lowest state ( 1Σ +): B e = 0.35236(6), α e = 0.00428(6), ΔG 1 2 = 683.107(1) ; upper state A( v = 4); T 4 = 17254.584(1), B 4 = 0.29296(4), ω e = 547(20); upper state B( v = 2): T 2 = 16475.002(1), B 2 = 0.29493(4), ω e = 585(20).