Fourier transform microwave/millimeter-wave spectroscopy of the ScC2 () radical: A model system for endohedral metallofullerenes

The pure rotational spectrum of the ScC2 radical ( X ̃ 2 A 1 ) has been measured using Fourier transform microwave/millimeter-wave techniques in the frequency range 15–63 GHz – the first high-resolution spectroscopic study of a 3d dicarbide species. ScC2 was created in a supersonic expansion from laser-ablated scandium and CH4 in the presence of a DC discharge. Four transitions, NKa,Kc = 101 → 000 through 404 → 303, were recorded, each consisting of multiple fine/hyperfine components; rotational, fine structure, and Sc(I = 7/2) hyperfine constants were determined. These measurements confirm the T-shaped geometry for ScC2, and suggest the molecule has significant covalent character.