The millimeter-wave spectrum of SrCCH(X2Σ+): chemical trends in metal monoacetylide species

The pure rotational spectrum of the SrCCH radical (X2Σ+) has been recorded using millimeter/sub-mm direct absorption techniques. SrCCH was synthesized in a dc discharge by the reaction of strontium vapor, produced in a Broida-type oven, and acetylene. Seventeen rotational transitions of this molecule were recorded in the range 248–370 GHz and fine structure splittings resolved. Rotational and spin-rotation parameters were determined using a 2Σ Hamiltonian. SrCCH appears to be linear with an ionic structure, as previously suggested. Comparison of structural parameters with MgCCH and CaCCH suggest subtle differences in the bonding of these monoacetylide species.