Bioluminescence is a phenomenon that has fascinated mankind for centuries. Today the phenomenon and its sibling, chemiluminescence, have impacted society with a number of useful applications in fields like analytical chemistry and medicine, just to mention two. In this review, a molecular-orbital perspective is adopted to explain the chemistry behind chemiexcitation in both chemi- and bioluminescence. First, the uncatalyzed thermal dissociation of 1,2-dioxetane is presented and analyzed to explain, for example, the preference for triplet excited product states and increased yield with larger nonreactive substituents. The catalyzed fragmentation reaction and related details are then exemplified with substituted 1,2-dioxetanone species. In particular, the preference for singlet excited product states in that case is explained. The review also examines the diversity of specific solutions both in Nature and in artificial systems and the difficulties in identifying the emitting species and unraveling the color...

Chemi- and Bioluminescence of Cyclic Peroxides.

An analysis is made of the various reactions in which ozone and atomic oxygen are involved in the stratosphere. At the present time, hydrogen, nitrogen, and chlorine compounds in the ranges parts per million, parts per billion, and parts per trillion may have significant chemical effects. In the upper stratosphere, above the ozone peak, where there is no strong departure from photochemical equilibrium conditions, the action of hydroxyl and hydroperoxyl radicals of nitrogen dioxide and chlorine monoxide on atomic oxygen and of atomic chlorine on ozone can be introduced. A precise determination of their exact effects requires knowledge of (1) the vertical distribution of the H2O, CH4, and H2 dissociation by reaction of these molecules with electronically excited oxygen atom O(¹D); (2) the ratio of the OH and HO2 concentrations and their absolute values, which depend on insufficiently known rate coefficients; (3) the various origins of nitric oxide production, with their vertical distributions related to latitude and season; and (4) the various sources giving different chlorine compounds that may be dissociated in the stratosphere. In the lower stratosphere, below the ozone peak, there is no important photochemical production of O3, but there exist various possibilities of transport. The predictability of the action of chemical reactions depends strongly on important interactions between OH and HO2 radicals with CO and NO, respectively, which affect the ratio n(OH)/n(HO2) at the tropopause level; between OH and NO2, which lead to the formation of nitric acid with its downward transport toward the troposphere; between NO and HO2, which lead to NO2 and its subsequent photodissociation; between ClO and NO, which also lead to NO2 and become more important than the reaction of ClO with O; and between Cl and various molecules, such as CH4 and H2, which lead to HCl with its downward transport toward the troposphere. All these chemical processes are subject to many changes since they occur in the lower stratosphere where seasonal, latitudinal, and even day-to-day variations of the ozone concentrations are observed in association with advective and dynamic transports, which depend on meteorological conditions as indicated by variations of tropopause heights.

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Stratospheric Ozone: An Introduction to Its Study

A new type of all-sky imager, using a high resolution, bare CCD, was operated at Utah State University Observatory at Bear Lake Utah during fall-winter, 1991–2 on clear nights. The purpose was to image OH airglow in the 7500–9000 A spectral region for correlative measurements with UARS satellite instrumentation. Examination of some 20 nights of data, some OH wave activity (interpreted as gravity wave phenomena) has been observed on all images and the spatial extent of the waves typically covered the entire viewing field (including overhead). Images are presented including examples of multiple wave sources and a (one time observed) complex breaking wave. The unique chaotic structure, which evolved over an hour, developed a distorted phase front followed by a very short wavelength ‘rippled’ structure.

OH emission and gravity waves (including a breaking wave) in all-sky imagery from Bear Lake, UT

The mechanism of the air-afterglow NO + O → NO2 + hν

NO2 fluorescence, excited by fixed visible frequencies of a Nd‐YAG laser, was measured as a function of time, pressure, and fluorescence wavelength. The low resolution fluorescence spectrum at all excitation wavelengths consists of strong banded features, assignable to ground state vibrational progressions, superimposed on an apparent continuum. The ratio of banded‐to‐continuum intensity decreases with increasing pressure, indicating that the continuum is partially of collisional origin at high pressures. There is also a red shift of fluorescence at high pressures, indicative of vibrational relaxation within the emitting state. A residual continuum is found under collision‐free conditions (0.1–0.01 mtorr) and ascribed to violation of the ΔK=0 selection rules in the initially excited levels of the highly perturbed 2B2 state. The time dependent decay of fluorescence excited at the banded features contains a fast component kB and a weaker, long‐lived component kC, identified with the underlying continuum. Ra...

Fluorescence lifetime studies of NO2. III. Mechanism of fluorescence quenching

The air glow reaction NO + O + (M) → NO*2 + (M) at low pressures

The air-afterglow reaction NO+O→NO2+hv involves a two-body radiative recombination at a rate of 4.2×10−18 cm3 molecule−1 sec−1, and a three-body process at a rate of 7×10−32 cm6 molecule−2 sec−1, with O2 as third body. Within the experimental error limit, the yield of the chemiluminescent three-body reaction coincides with the over-all termolecular combination of NO with O. The recombination mechanism consists of the formation of unbound molecules [NO2*] which are in equilibrium with the edicts with an equilibrium constant of 2×10−22 cm3 molecule−1 and of subsequent competitive stabilization by radiation and by vibrational relaxation which removes an average energy of about 800 cm−1 per gas-kinetic collision with M=O2. As with O2, the energy-transfer mechanism also predominates with other third bodies, such as He, Ne, Ar, H2, and N2. With CO2 and SF6, the air afterglow may involve different elementary steps.

Mechanism of the air afterglow NO+O→NO2+hv

Untersuchungen in der „Großen Bonner Kugel”

The increase of the emission intensity of the chemiluminescent reaction due to a third body M was first shown in 1967 in the pressure region of 3 to 20 mTorr (Becker et al., 1967, 1968a). Although these findings were confirmed independently by two other groups (Jonathan and Petty, 1968; McKenzie and Thrush, 1968), experimental limitations did not permit interpreting these results as definitive evidence against a two-body mechanism for the airglow reaction in the pressure region of 1 to 100 mTorr (Reeves et al., 1964).

D. Thran

Papers

The mechanism of the air-afterglow NO + O → NO2 + hν

The air glow reaction NO + O + (M) → NO*2 + (M) at low pressures

Mechanism of the air afterglow NO+O→NO2+hv

Untersuchungen in der „Großen Bonner Kugel”

The Airglow Reaction NO+O+(M)→NO2*at Low Pressures