The collisions between two oxygen molecules give rise to O4 absorption in the Earth atmosphere. O4 absorption is relevant to atmospheric transmission and Earth’s radiation budget. O4 is further used as a reference gas in Differential Optical Absorption Spectroscopy (DOAS) applications to infer properties of clouds and aerosols. The O4 absorption cross section spectrum of bands centered at 343, 360, 380, 446, 477, 532, 577 and 630 nm is investigated in dry air and oxygen as a function of temperature (203–295°K), and at 820 mbar pressure. We characterize the temperature dependent O4 line shape and provide high precision O4 absorption cross section reference spectra that are suitable for atmospheric O4 measurements. The peak absorption cross-section is found to increase at lower temperatures due to a corresponding narrowing of the spectral band width, while the integrated cross-section remains constant (within o3%, the uncertainty of our measurements). The enthalpy of formation is determined to be ΔH250 = -0.12±0.12 kJ mol-1, which is essentially zero, and supports previous assignments of O4 as collision induced absorption (CIA). At 203°K, van der Waals complexes (O2-dimer) contribute less than 0.14% to the O4 absorption in air. We conclude that O2-dimer is not observable in the Earth atmosphere, and as a consequence the atmospheric O4 distribution is for all practical means and purposes independent of temperature, and can be predicted with an accuracy of better than 10-3 from knowledge of the oxygen concentration profile.
PCCP publishes new, original research, covering the areas of physical chemistry, chemical physics and biophysical chemistry, and includes papers on: biophysical chemistry, chemisorption and heterogeneous catalysis, clusters, colloid and interface science, computational chemistry and molecular dynamics, electrochemistry, energy transfer and relaxation processes, gas-phase kinetics and dynamics, laser-induced chemistry, liquids and solutions, materials science, molecular beam kinetics and spectroscopy, photochemistry and photophysics, physical chemistry of macromolecules and polymers, physisorption and chromatographic science, quantum chemistry and molecular structure, radiation chemistry, reactions in condensed phases, solid-state chemistry (microstructures and dynamics), spectroscopy of molecules and gas-phase complexes spectroscopy, statistical mechanics and quantum theory of the condensed phase, statistical mechanics of gaseous molecules and complexes, surface science, thermodynamics, zeolites and ion-exchange phenomena
The RSC is the largest organisation in Europe for advancing the chemical sciences. Supported by a worldwide network of members and an international publishing business, our activities span education, conferences, science policy and the promotion of chemistry to the public.
The absorption spectrum of O2 and O2‐O2 collision pairs were measured over the wavelength range from 330 to 1140 nm using pressures of O2 from 1 to 55 atm at 298 K. Absorption cross sections, pressure dependences, band centers, and full widths at half maximum of the observed absorption bands centered at 343.4, 360.5, 380.2, 446.7, 477.3, 532.2, 577.2, 630.0, 688, 762, and 1065.2 nm are reported. The absorption bands centered at 360.5, 380.2, and 477.3 nm were also measured at 196 K and their temperature dependences were characterized.
