Fourier transform microwave spectroscopy of LiCCH, NaCCH, and KCCH: Quadrupole hyperfine interactions in alkali monoacetylides

► Microwave spectra of LiCCH, NaCCH, KCCH and deuterium isotopologues recorded using FTMW spectroscopy. ► Combined fit of microwave and previous millimeter-wave data. ► Metal and deuterium quadrupole coupling constants determined for the first time. ► Synthesized by ablation of the pure metal and reaction with acetylene using discharge assisted laser ablation.