Endothermic energy

Endothermic energy transferred from surroundings to system... 

The reaction is endothermic. Energy from sunlight is stored in the form of high-energy C-C bonds (e.g., organic biomass) and O2, the raw materials for the support of hetero-trophic organisms dependent upon the food source. 

C. Adachi, R.C. Kwong, P. Djurovich, V. Adamovich, M.A. Baldo, M.E. Thompson, and S.R. Forrest, Endothermic energy transfer a mechanism for generating very efficient high-energy phosphorescent emission in organic materials, Appl. Phys. Lett., 79 2062-2064 (2001). 

Thus the complete removal of an electron will undoubtedly require a prohibitively endothermic energy, I — <, as pointed out by Emmett and Teller (20). Such a view uses the concept of the removal of the electron to an infinite distance. If, however, the electron is moved to a finite distance in the solid (that is, partial ionization), the energy required, I, is less than I, and the small dipole moment of the chemisorption bond can be explained. Dowden takes care of this partial ionization by introducing the term without actually specifying the physical mechanism of the electron transfer. 

Photophysical energy transfer between the initially populated dye excited state (which is itself incapable of initiation) and other chromophores which, if populated, would yield free radical initiating species, is generally disfavored energetically. Nonclassical endothermic energy transfer processes are required. Alternatively, other processes which avoid typical energy transfer restrictions must be devised. Exciplex mediated electron transfer processes represent one such alternative. 

Initiation normally requires molecules with weak bonds to undergo homolytic cleavage to produce free radicals. Since bond homolysis even of weak bonds is endothermic, energy in the form of heat (A) or light (hv) is usually required in die initiation phase. However, some type of initiation is required to get any free-radical reaction to proceed. That is, you must first produce free radicals from closed-shell molecules in order to get free-radical reactions to occur. Benzoyl peroxide contains a weak 0-0 bond that undergoes thermal cleavage and decarboxylation (probably a concerted process) to produce phenyl radicals which can initiate free-radical chain reactions. 

Have you ever noticed that perfume or rubbing alcohol feels cool on your skin as it evaporates The physical process of evaporation is endothermic. Energy is taken away from the surface of your skin, so you feel cool. The energy is added to the liquid alcohol or perfume solvent to make it a gas. The following equation shows the endothermic evaporation of isopropanol (a type of rubbing alcohol) from a liquid to a gas ... 

Examination of the equilibrium conditions shows that the equilibrium constant for intrinsic disorder (Equation 1) involves only the (endothermic) energy needed to create a complementary pair of defects in the ordered, stoichiometric crystal lattice. Writing Nh, Nl as the number of cation vacancies and of interstitial cations, respectively, in a stoichiometric crystal with N lattice sites in all, at an expenditure of energy denoted by Eh, respectively, then the intrinsic disorder, f, is given by Equation 5. 

All ionisation energies have positive values - i.e. they are endothermic. Energy is required to pull an electron off any atom. 

For the H2 and Bi2 reaction, in which IS.H is negative, the total energy of the reaction decreases. Energy cannot disappear, so what happens to the energy The energy is released as heat by the system. If the reaction was endothermic, energy in the form of heat would be absorbed by the system and the enthalpy would increase. 

Perspiration is a mechanism by which your body passes water to the surface of your skin via sweat glands. The vaporization of water is an endothermic (energy-absorbing) process, and as the water evaporates, it removes heat from the surface of your skin. 

We have shown an extreme enhancement of the exciplex emission in bilayer EL as compared to PL and the appearance of weak exciton EL only through thermal activation from the exciplex at higher temperatures. At low temperatures, the exciton contribution is frozen out completely and only exciplex electroluminescence is seen. This demonstrates unambiguously that the only source of bulk excitons during electrical excitation is endothermic energy transfer from exciplex states that are generated via barrier-free electron-hole capture and confirms the work presented in Section 2.2.1 that was based on room-temperature emission from polymer blend LEDs and time-resolved PL. 

To achieve spectral sensitization by singlet energy transfer with a sensitizer that absorbs at a longer wavelength than the reactant would require endothermic energy transfer, which under normal circumstances is not a practical solution. However, it is possible to accomplish this with a sensitizer whose singlet excited state lies below that of the reactant, but whose triplet level lies above the triplet... 

Endothermic energy as heat flows into a system... 

Transient absorption measurements of the TIPS-tetracene solutions revealed the presence of three distinct states in concentrated solutions. An intermediate was observed that displayed a lifetime identical to the emissive excimer from PL. Formation of the intermediate quenched the singlet exciton emission with a 70 ps lifetime and led to subsequent triplet exciton formation in a 120% yield. The free triplet exciton population rose over the first ten nanoseconds, consistent with thermal dissociation of the excimer intermediate over the endothermic energy barrier. 

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