Electron spin resonance of the boron trimer

Abstract
The 11B3 molecule, observed in neon, argon, and krypton matrices at 4 K has D3h symmetry and a 2A′1 ground state. the isotropic hyperfine tensor indicates ∼15% s hybridization of the in-plane p-bonded orbital of the unpaired spin and rapid rotation of the trimer in the solids.