Visible and infrared spectra of the solids α- and β-O2 at 9–30 K

Abstract

ABSTRACT To establish the spectroscopy of the solids α- and β-oxygen, we measured the thermal ramping spectra of the solid O2 in visible and near-infrared (near-IR) wavelength range 450–1020 nm and mid-infrared (mid-IR) range 500–5000 cm−1 (2–20 μm) at temperature 9–30 K. Besides the solids α- and β-oxygen, the imperfect structure of O2 ice might co-exist at low temperature. In mid-IR spectra, a triplet was observed at 1545.7, 1548.1, and 1549.6 cm−1 associated to the imperfect crystallinity of solid O2; the triplet existed below 27 K, but not at 30 K and on re-cooling to 9 K. The spectra measured at re-cooled 9 and 30 K are evidently responsible only for the solids α- and β-O2, respectively; overall, the spectra of the solids α- and β-O2 appear similar in the visible region, but those differ significantly from the spectrum of the solid O2 contaminated with imperfect structure. For solid α-O2, IR lines were recorded at 1591 and 1617 cm−1, which exhibited a reversible behaviour through the α-β phase transition temperature at 24 K. The visible spectrum of the separate solid α-O2 was obtained for the first time.