Visible, near-infrared and mid-infrared spectra of solid O2 at 6–33 K

Abstract

ABSTRACT We report spectra in the visible and near-infrared wavelength range 350–1155 nm and in the mid-infrared range 500–5000 cm–1 (2–20 $\mu$m) of molecular oxygen at temperatures 6–33 K. In mid-infrared spectra, a sharp line at 1552.4 cm–1 was observed at a deposition temperature of 6 K. The intensity, profile and position of this feature depended sensitively upon the deposition temperature as a result of a connection with lattice imperfections; instead, a triplet feature at 1545.7, 1548.1 and 1549.6 cm–1 appeared at temperatures 9 and 12 K, but disappeared at 18, 24 and 30 K. Additional infrared lines of solid α-O2 were observed at 1591 and 1617 cm–1, which exhibited a reversible behaviour through the α–β phase transition temperature at 24 K. The transmissions of solid O2 showed nearly no change in wavenumber range 500–2000 cm–1 (5–20 $\mu$m) at temperatures 6–33 K; above 2000 cm–1 (<5 $\mu$m), the transmission of solid O2 depended strongly on temperature. Roughly, the transmission of solid O2 at temperatures 6–21 K fluctuated slightly in the visible and near-infrared region, whereas it decreased greatly at 24 K and continuously diminished further at higher temperatures. Notably, a broad absorption of solid β-O2 was observed in the wavelength region 350–700 nm at temperatures 27, 30 and 33 K.