Oxygen collision-induced absorptions

Mlawer, E. J S. A. Clough, P. D. Brown, T. M. Stephen, J. C. Landry, A. Goldman, and F. J. Murcray, Observed Atmospheric Collision-Induced Absorption in Near-Infrared Oxygen Bands, J. Geophys. Res., 103, 3859-3863 (1998). 

Historically, collision-induced absorption was discovered in the fundamental band of oxygen and nitrogen [128], Fig. 1.1. Literally, any molecular complex may be expected to have more or less prominent induced bands in the fundamental band and overtone regions of the molecules involved-besides the rototranslational bands considered above. Induced vibrational spectra are indeed known for many molecular systems and selected examples will be discussed below. Since in virtually all of these spectra rotation and vibration are coupled, we will generally refer to these as rotovibrational induced spectra. 

A computational study of the density dependence of the rototrans-lational collision-induced absorption spectrum of nitrogen, oxygen and carbon dioxyde was reported by Steele and Birnbaum [375] on the basis of the classical quadrupole induction model. 

Both photon-assisted collisions and collision-induced absorption deal with transitions which occur because a dipole moment is induced in a collisional pair. The induction proceeds, for example, via the polarization of B in the electric multipole field of A. A variety of photon-assisted collisions exist for example, the above mentioned LICET or pair absorption process, or the induction of a transition which is forbidden in the isolated atom [427], All of these photon-assisted collision processes are characterized by long-range transition dipoles which vary with separation, R, as R n with n — 3 or 4, depending on the symmetry of the states involved. Collision-induced spectra, on the other hand, frequently arise from quadrupole (n = 4), octopole (n = 5) and hexadecapole (n = 6) induction, as we have seen. At near range, a modification of the inverse power law due to electron exchange is often quite noticeable. The importance of such overlap terms has been demonstrated for the forbidden oxygen —> lD emission induced by collision with rare gases [206] and... 

Collision-induced absorption has been studied in the laboratory in various dense gases besides hydrogen and mixtures of hydrogen and helium, especially in oxygen, nitrogen, methane, etc., and mixtures of such gases which are of interest in the atmospheres of the inner planets [5, 131, 58],... 

Calculations of the rototranslational absorption spectra of nitrogen, oxygen, and nitrogen-oxygen mixtures were communicated [104]. Similar work for the fundamental band of oxygen was reported [77]. Collision-induced absorption spectra of O2-N2, O2-CO2, and O2-H2O pairs involving a — X and b <— X electronic transitions of O2 have been studied theoretically [105, 106]. 

Collision-induced absorption of gaseous oxygen in the Herzberg continuum, p. 183, 2003. In Ref. [10]. 

A. Goldman, and F. J. Murcray. Observed atmospheric collision-induced absorption in near infrared oxygen bands. J. Geophys. Res., 103 3859, 1998. 

Collision-induced electronic spectra have many features in common with rovibrotranslational induced absorption. In this Section, we take a look at the electronic spectra. We start with a historical note on the famous forbidden oxygen absorption bands in the infrared, visible and ultraviolet. We proceed with a brief study of the common features, as well as of the differences, of electronic and rovibrotranslational induced absorption. Recent work is here considered much of which was stimulated by the advent of the laser - hence the name laser-assisted collisions. The enormous available laser powers stimulated new research on laser-controlled, reactive collisions and interactions of supermolecules with intense radiation fields. In conclusion, we attempt a simple classification of various types of electronic collision-induced spectra. 

G. C. Tabisz, E. J. Allin, and H. L. Welsh. Interpretation of the visible and near infrared absorption spectra of compressed oxygen as collision induced electronic transitions. Can. J. Phys., 47 2859, 1969. 

Similar to H+ implantation, optimized MgO thin films have been implanted with 1.5 MeV Li+ ions for various fluences (lO MO ions cm ). Irradiation of crystalline MgO with energetic metal ions produces stable vacancies and interstitials in the anion sublattice. Elastic collisions with energetic particles also produce cation vacancies, but these defects do not survive because the cation interstitials quickly recombine with the vacancies. Optical absorption bands can monitor these defects induced by ion implantation. Similar observations have been already done on MgO crystals after neutron irradiation (Kappers et al. 1970, Monge et al. 2000). In crystalline MgO material irradiated with Li+ ions, the well-known defects are (1) oxygen vacancies (primarily the one-electron F center), (2) oxygen divacancies Fj, (3) V and V centers (cation vacancies that have trapped one or two holes, respectively) produced by the capture of holes by existing vacancies, and (4) an unidentified defect that absorbs at 2.16 eV (572 nm) (Gonzales et al. 1991). 

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