ESR of GdF3 and related molecules at 4 °K

The pyramidal (C3v) GdF3 molecule was trapped in neon and argon matrices at 4°K and its ESR spectrum measured in the X-band region. In neon the spectrum exhibited several off-principal-axis transitions which were sensitive to the assigned magnetic parameters. It was shown to be a S = 7/2 molecule (ground state 8A1) with g∥ = 1.995, g⊥ = 1.990, and ‖ D ‖ = 0.433 cm−1. The 19F hfs was unresolved and therefore <∼10 G. Only the mS = +1/2 ↔ −1/2 transition of GdH3 was observed, yielding ‖ D ‖ = 0.7 to 1.3 cm−1, and it is inferred to be a planar (D3h) molecule (ground state 8A1′). Weak spectra of GdCl3 (8A1) and GdF2 (9A1) were also observed, yielding ‖ D ‖?0.36 and 0.20 cm−1, respectively.