A high-resolution laser ablation study of the A˜2Π-X˜2Σ+ transition of SrCCH

The laser-induced excitation spectrum of the A˜2Π-X˜2Σ+ transition of SrCCH has been recorded at high resolution. A rotational analysis has been performed yielding rotational and fine structure parameters for the à state. In addition, a vibrational frequency for the Sr-C stretch (ν3) in the Ã2Π state has been determined. Using the rotational constant of the à state, the Sr-C bond length was determined to be 2.43 Å, which is ∼0.03 Å shorter than in the ground state. A comparison of the Λ-doubling constant p, to those of the other alkaline-earth acetylides suggests that SrCCH and CaCCH appear to follow the pure precession model unlike MgCCH. Finally, a search for the B˜2Σ+-X˜2Σ+ transition was negative, as with CaCCH, suggesting that the B˜ state may be predissociative.