The liquid phase photochemical exchange between chlorine and carbon tetrachloride was more reproducible than the thermal exchange, although still erratic.

The photochemical exchange in the gas phase.

-- Although there was some variation in results which must be attributed either to trace impurities or to variation in wall effects, the photochemical exchange in the gas phase was sufficiently reproducible so that it seemed meaningful to compare the reaction rates in different series of reaction tubes for the purpose of obtaining information on the effect of chlorine concentration and of carbon tetrachloride concentration on the reaction rate.

Other photochemical cycloaddition reactions with alkenes occur through excimers.

Chemistry is also concerned with the interactions between atoms ( or groups of atoms ) and various forms of energy ( e. g. photochemical reactions, changes in phases of matter, separation of mixtures, properties of polymers, etc.

Modern smog, as found for example in Los Angeles, is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

It is also greatly absorbed by the atmosphere, and along with UVC is responsible for the photochemical reaction leading to the production of the ozone layer.

This work was extended in 1973 to include the effects of nitrogen and hydrogen reactions with his former Ph. D. student, Donna Blake, in Effect of photochemical models on calculated equilibria and cooling rates in the stratosphere.

In 1967, along with his NCAR colleague, Douglas D. McKenzie, Lindzen extended the theory to include a term for Newtonian cooling due to emission of infrared radiation by carbon dioxide in the stratosphere along with ozone photochemical processes, and then in 1968 he showed that the theory also predicted that the semi-diurnal oscillation would be insensitive to variations in the temperature profile, which is why it is observed so much more strongly and regularly at the surface.

Becquerel was associated with his father in much of his work, but he himself paid special attention to the study of light, investigating the photochemical effects and spectroscopic characters of solar radiation and the electric light, and the phenomena of phosphorescence, particularly as displayed by the sulfides and by compounds of uranium.

In an industrial application, about 100, 000 tonnes of benzyl chloride are prepared annually by the gas-phase photochemical reaction of toluene with chlorine.

Another example is a photochemical cycloaddition with two alkene groups tethered through a silicon acetal group ( racemic, the other enantiomer not depicted ), which is subsequently cleaved by TBAF yielding the endo-diol.

In the DeMayo reaction 1, 3-diketones react with alkenes in a photochemical pericyclic reaction to form ( substituted ) 1, 5-diketones.

Chapman is credited with working out, in 1930, the photochemical mechanisms that give rise to the ozone layer.

The tert-butyl derivative was first synthesised starting from a cycloaddition of an alkyne with t-Bu substituted maleic anhydride, followed by rearrangement with carbon dioxide expulsion to a cyclopentadienone and its bromination, followed by addition of the fourth t-Bu group and a photochemical rearrangement with expulsion of carbon monoxide.

The definitions of VOCs used for control of precursors of photochemical smog used by EPA, and U. S. States with their own outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process.

Ultraviolet light with wavelengths shorter than 400 nm tends to be absorbed in the cornea and lens, where it can produce injuries at relatively low powers due to photochemical damage.

There are two types of photochemical systems with photocatalysis.

Following the Woodward-Hoffmann rules, the photochemical 6π cyclization takes place in a conrotatory fashion, leading to products with an anti configuration of the methyl substitutents.

The nitric acid in polar stratospheric clouds reacts with CFCs to form chlorine, which catalyzes the photochemical destruction of ozone.

Since photochromism is just a special case of a photochemical reaction, almost any photochemical reaction type may be used to produce photochromism with appropriate molecular design.

Next the methyl substituents are functionalized with bromine groups by the photochemical reaction with N-bromosuccinimide or NBS.

For each photon of light absorbed by a chemical system, no more than one molecule is activated for a photochemical reaction, as defined by the quantum yield.

* Quantum yield of the photochemical reaction.

The Grotthuss – Draper law ( for chemists Theodor Grotthuss and John W. Draper ) states that light must be absorbed by a chemical substance in order for a photochemical reaction to take place.

It would appear that it should be possible to determine unique mechanisms for the thermal and photochemical reactions in both the liquid and gas phases and to determine values for activation energies of some of the intermediate reactions of atoms and free radicals, as well as information on the heat of dissociation of the carbon-halogen bond.

The liquid phase photochemical reaction.

With a few exceptions related to high-energy photons ( such as fluorescence, harmonic generation, photochemical reactions, the photovoltaic effect for ionizing radiations at far ultraviolet, X-ray, and gamma radiation ), absorbed electromagnetic radiation simply deposits its energy by heating the material.

* Photosystem II inhibitors reduce electron flow from water to NADPH2 + at the photochemical step in photosynthesis.

In fact, Lindzen's, Radiative and photochemical processes in mesospheric dynamics, Part II: Vertical propagation of long period disturbances at the equator, documented the failure of this attempt to explain the QBO.

Hydrocarbon solvents absorb only at short wavelengths and are thus preferred for photochemical experiments requiring high energy photons.

* Transparency ( photography ), a still, positive image created on a transparent base using photochemical means

Several important applications of astrography, including astronomical spectroscopy and astrometry require greater dimensional stability than film could provide, and continued using plates until digital imaging improved to the point of supplanting photochemical photography for these purposes.

In 2008, Princeton chemistry professor Andrew B. Bocarsly reported the direct conversion of carbon dioxide and water to methanol using solar energy in a highly efficient photochemical cell .< ref name = Barton >

The photochemical reaction cells consisted of 10 mm. i.d. Pyrex tubing, 5.5 cm. long, diffraction effects being minimized by the fact that the light passed through only liquid-glass interfaces and not gas-glass interfaces.

In photochemical reactions, atoms and molecules absorb energy ( photons ) of the illumination light and convert into an excited state.

Wilhelm Homberg described how light darkened some chemicals ( photochemical effect ) in 1694.

It is the antithesis of a photochemical reaction, in which light is used to drive an endothermic chemical reaction.

In case of photochemical reactions light provides the activation energy.

Norrish type II reactionIn the area of photochemistry, a photochemical reaction is a chemical reaction that is induced by light.

Certain species of carbon nanotubes also undergo photochemical reactions when exposed to intense pulsed light from a laser, arc lamp, or flashbulb.

* Different types of glazing can show a variety of chromic phenomena, that is, based on photochemical effects the glazing changes its light transmission properties in response to an environmental signal such as light ( photochromism ), temperature ( thermochromism ), or voltage ( electrochromism ).

Another mechanism is photochemical damage, where light triggers chemical reactions in tissue.

Wilhelm Homberg described how light darkened some chemicals ( photochemical effect ) in 1694.