Fourier transform microwave spectroscopy of metal nitrides and imides: Quadrupole structure in ScN (X1Σ+), YN (X1Σ+), and BaNH (X∼1

Lindsay N. Zack

¹

,

Matthew P. Bucchino

²

,

M. K. L. Binns

³

et al.

Abstract

Pure rotational spectra of ScN, YN and BaNH in their 1  + ground electronic states were recorded in the 15 -55 GHz region using Fourier transform microwave/millimeter-wave spectroscopy. Hyperfine components arising from the J = 1 → 0 transitions were measured for all three molecules, and for YN, in the J = 2 → 1 line, as well. The 15 N isotopologues were also observed for the nitride species. The molecules were created in a supersonic jet by the reaction of metal vapor with ammonia using a discharge-assisted laser ablation source (DALAS). From these data, electric quadrupole and nuclear spin rotation hyperfine parameters were determined for the nitrogen nucleus in all species; metal hyperfine constants were additionally measured for ScN and YN. DFT calculations using the B3LYP functional were also performed to help aid in spectral assignments. For ScN, the scandium quadrupole coupling constant (eQq = 33.818(19) MHz) was found to be considerably smaller than in the corresponding halides, suggesting a different electronic structure. The nitrogen coupling constant for ScN is consistent with a more covalent molecule, perhaps even a diradical structure as well. In BaNH, a relatively small value of the nitrogen quadrupole coupling constant of eQq = 0.039 (11) MHz was determined, attributable to the non-terminal position of the nitrogen atom and the Ba-N triple bond.