ESR and Optical Spectroscopy of ScO, YO, and LaO in Neon and Argon Matrices; Establishment of Their Ground Electronic States

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Abstract
ScO, YO, and LaO were vaporized from the solid oxides at temperatures near 2500°K and trapped in neon and argon matrices at 4° and 20°K. ESR spectra of these matrices show that the ground states of all of the molecules are 2Σ. The measured magnetic parameters for the three molecules are as follows: ScO, g=2.00±0.01, A=2.01±0.01 kMc/sec; YO, g=2.003±0.002, A=0.803±0.003 kMc/sec; LaO, g=2.01±0.01, A=3.89±0.01 kMc/sec. The A values then yield nuclear hyperfine‐structure separations (Δν) of 0.27, 0.03, and 0.52 cm−1, respectively, and explain the large splittings observed in the optical spectra of ScO and LaO. The optical spectra of the matrices exhibit the two transitions A2Π←X2Σ and B2Σ←X2Σ observed in the gas spectra of these molecules. The bands are exceptionally broad and shifted in the matrix relative to the gas, much more so than in the matrix spectra of other transition‐metal diatomic oxides. Illumination of the matrices with tungsten light leads to a gradual disappearance of the absorption bands and loss of color. The ESR and infrared signals are similarly affected. An explanation of this bleaching phenomenon is offered which involves diffusion and reaction of excited M—O molecules in the matrix. New bands appear in the LaO—neon matrix during illumination and are tentatively attributed to LaO molecules in more ``gas‐like'' sites.

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