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Phosphorescent materials continue to emit light for some time after the radiation stops. This difference in timing is a result of quantum spin effects. Fluorescence occurs when a photon of the incoming radiation is absorbed by a molecule exciting it to a higher energy level followed by emission of light as the molecule returns to a lower energy ...
A vapor can exist in equilibrium with a liquid (or solid), in which case the gas pressure equals the vapor pressure of the liquid (or solid). A supercritical fluid (SCF) is a gas whose temperature and pressure are above the critical temperature and critical pressure respectively. In this state, the distinction between liquid and gas disappears.
Liquid crystal: Properties intermediate between liquids and crystals. Generally, able to flow like a liquid but exhibiting long-range orientational order. Supercritical fluid: A fluid with properties intermediate of liquids and gasses. At sufficiently high temperatures and pressures, the distinction between liquid and gas disappears, resulting ...
A similar concept applies to liquid–gas phase changes. [7] Water is an exception which has a solid-liquid boundary with negative slope so that the melting point decreases with pressure. This occurs because ice (solid water) is less dense than liquid water, as shown by the fact that ice floats on water.
The transition from solid to liquid, and gas to liquid (shown by the white condensed water vapour). Other phase changes include: Transition to a mesophase between solid and liquid, such as one of the "liquid crystal" phases. The dependence of the adsorption geometry on coverage and temperature, such as for hydrogen on iron (110).
Atomic Fluorescence Spectroscopy (AFS) techniques are useful in other kinds of analysis/measurement of a compound present in air or water, or other media, such as CVAFS which is used for heavy metals detection, such as mercury. Fluorescence can also be used to redirect photons, see fluorescent solar collector.
More directly, dyes can be added to (usually liquid) flows to measure concentrations; typically employing the light attenuation or laser-induced fluorescence techniques. In scientific visualization flows are visualized with two main methods: Analytical methods that analyse a given flow and show properties like streamlines, streaklines, and ...
Transition metal compounds are often colored because of transitions of electrons between d-orbitals of different energy. (see Transition metal#Colored compounds ). Organic compounds tend to be colored when there is extensive conjugation , causing the energy gap between the HOMO and LUMO to decrease, bringing the absorption band from the UV to ...