Quenching of angular momentum in the ground states of VC, NbC, VSi, and NbSi molecules

The electron spin resonance spectra of VC, VSi, NbC, and NbSi trapped in the solid rare gases (Ne, Ar, Kr) show, principally through the large negative values of Δg∥=g∥−ge, that the orbital angular moments of these molecules in their (proposed) ground 2Δ states are partially quenched. Observed metal hyperfine splittings also vary with the matrix gas. This unprecedented effect in rare-gas matrices is attributed to strong unsymmetrical interaction of these ionic molecules with the matrix such that each is situated in an orthorhombic crystal field. The crystal-field-splitting parameter δ is both molecule and matrix dependent, varying from approximately 1400 to 7800 cm−1.