High spin molecules: ESR and optical spectroscopy of MnH (7Σ) and MnH2 (6A1) at 4 °K

1 September 1978

journal article
research article
Published by AIP Publishing in The Journal of Chemical Physics

Vol. 69 (5) , 1869-1875
https://doi.org/10.1063/1.436823

Abstract

MnH and MnH₂ molecules, and their deuterated counterparts, have been trapped in argon and neon matrices at 4 °K and observed via infrared, visible, and electron‐spin‐resonance spectrscopy. The data for MnH support the gas‐phase ⁷Σ ground‐state assignment and yield the magnetic parameters ‖A (H) ‖?20, ‖A_∥(Mn) ‖=322(6), ‖A_⊥(Mn) ‖=299(2) MHz, g_⊥=2.001(1) (assuming g_∥ =g_e), D=−0.002(1) cm⁻¹. The derived MO description is in essential agreement with the ab initio calculations of Bagus and Schaefer. Infrared data indicate that MnH₂ is bent at a bond angle of 117±30°, and stretching force constants are derived. ESR spectra variations with the matrix used and with isotopic substitution indicate motional effects in some matrices. It is concluded that the ground state is ⁶A₁ with ‖D‖=0.20(2) cm⁻¹ and with the probable hyperfine parameters ‖A (H) ‖=36, ‖A_xy(Mn) ‖ =73 MHz, where xy is an average axis perpendicular to the H–H direction. The bent molecule is justified by Walsh‐type theory applied to transition‐metal dihydrides. There are indications that the MnH₃ molecule may have also been observed.

Keywords

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