Emission ultraviolet

White Phosphorus Oxidation. Emission of green light from the oxidation of elemental white phosphoms in moist air is one of the oldest recorded examples of chemiluminescence. Although the chemiluminescence is normally observed from sotid phosphoms, the reaction actually occurs primarily just above the surface with gas-phase phosphoms vapor. The reaction mechanism is not known, but careful spectral analyses of the reaction with water and deuterium oxide vapors indicate that the primary emitting species in the visible spectmm are excited states of (PO)2 and HPO or DPO. Ultraviolet emission from excited PO is also detected (196). 

Some of the investigations carried out in the first half of the twentieth century were related to CL associated with thermal decomposition of aromatic cyclic peroxides [75, 76] and the extremely low-level ultraviolet emission produced in different reaction systems such as neutralization and redox reactions involving oxidants (permanganate, halogens, and chromic acid in combination with oxalates, glucose, or bisulfite) [77], In this period some papers appeared in which the bright luminescence emitted when alkali metals were exposed to oxygen was reported. The phenomenon was described for derivatives of zinc [78], boron [79], and sodium, potassium, and aluminum [80]. 

Structure. The ultraviolet emission spectrum of CF2 was first examined by Venkateswarlu 2 9, who prepared the molecule by passing an uncondensed transformer discharge through CF4. An extensive band system between 3250 and 2400 A was observed. The similarity of the band system to that of N02 suggested that a non-linear triatomic molecule was responsible for the spectrum. Venkateswarlu identified the band system with the transition 1B2 - 1 Aj. 

Nonradiative energy transfer is very often used in practical applications, such as to enhance the efficiency of phosphors and lasers. A nice example is the commercial phosphor Cas(P04)3 (FCl), which is doubly activated by Sb + and Mn + ions. When the phosphor is singly activated by Mn + ions, it turns out to be very inefficient, due to the weak absorption bands of the divalent manganese ion. However, coactivation with Sb + ions produces a very intense emission from the Mn + ions, because the Sb + ions (the donor centers) efficiently absorb the ultraviolet emission (253.6 nm) of... 

A light source, which is usually tungsten for measurements in the visible range (350-800 nm) or deuterium for ultraviolet emission (200-350 nm). 

Many methods, including classical wet chemistry, ultraviolet emission spectrography, polarography and, latterly, neutron activation, have been used to measure the concentration of gold in plasma, but have not found general acceptance in clinical laboratories. The availability of methods using atomic absorption (D12, L13) puts the assay within the scope of any well equipped clinical laboratory. 

If a single crystal of ZnO which emits no ultraviolet radiation is ground up to increase its surface area, it still does not show any ultraviolet emission. According to Fig. 2, little oxygen adsorption can occur at room temperature. If it is correct to assume (33) that in sintered samples or powders the density of interstitial zinc is higher near the surface than in the bulk, then it is obvious that in a single crystal, with its constant density, the adsorption will be even lower. 

ES—ultraviolet emission spectrometry, direct reading type... 

Time resolved ultraviolet emission spectroscopy of acetylene—oxygen explns has been used to compute free radical concns (Refs 30 35). 

Parra E, Alexeev I, Fan J, Kim KY, McNaught SJ, Milchberg HM (2000) X-ray and extreme ultraviolet emission induced by variable pulse-width irradiation of Ar and Kr clusters and droplets. Phys. Rev. E 62 R5931-R5934... 

The work of Neuimin and Terenin86 on the photolysis of water is to be regarded as classical. They studied the near ultraviolet emission produced when H20 is subjected to vacuum ultraviolet radiation from a hydrogen discharge. They associated the emission correctly with an electronic transition of the OH free radical. The energetics of the dissociation of water are presented in Table XII. 

The a3 n state of CO was first identified through its ultraviolet emission spectrum to the ground state, producing what are now known as the Cameron bands [160, 161, 162], Its radioffequency spectrum was then described by Klemperer and his colleagues in a classic series of molecular beam electric resonance experiments. Its microwave rotational spectrum was measured by Saykally, Dixon, Anderson, Szanto and Woods [163], and the far-infrared laser magnetic resonance spectrum was recorded by Saykally, Evenson, Comben and Brown [164], In the infrared region both electronic... 

Key words Electroluminescence, epitaxial layers, heterojunction, hole injection, ultraviolet emission... 

The CL spectrum of the ZnO film consisted of intense, near-band-edge ultraviolet emission with a wavelength maximum at 387 nm and a full width at half maximum of 21 nm. This emission is of excitonic nature and is a result of the radiative annihilation of free and bound excitons. A broad defect-related green band with much lower intensity near 510 nm, typical for ZnO, was also observed (Fig. 1). The CL spectrum of the p-Alo. i2Gao 8sN(Mg) film consisted of a very weak near-band-edge emission with at 356 nm, and of a more intense broad band with a maximum at 410 nm. 

Emeleus and Purcell examined the emission of P2O5 excited by the absorption of radiation. They found no ultraviolet emission and confirmed the earlier results of Ebert and Hoffmann that the visible emission was continuous with maximum intensity in the green. On the other hand, an electrical discharge through P2O5 vapor gave a complex band system, in which were included the bands of the spectrum of glowing phosphorus. 

As mentioned above, the nonequilibrium radiation code NEQAIR is employed for prediction of ultraviolet emission from the DSMC flow field solutions. The modeling of ultraviolet emission with this code is discussed for nitric oxide in Ref. 84 and for atomic oxygen in Ref. 87. A common assumption made in using the NEQAIR code is that a quasisteady state (QSS) exists for the number densities of the electronically excited species. The assumption requires that the time scale of chemical processes is much smaller than the time scales for diffusion and for changes in overall properties. Under these conditions, the local values of temperatures and ground state species number densities obtained from the DSMC computation may be used to compute the populations of the electronically excited states. 

The decomposition of carbon monoxide is a good example of a complex dissociation process for a diatomic molecule. The reaction has been studied over the temperature range 6000—15,000°K using pure CO [124] and dilute mixtures in argon [125—127] by the techniques of infrared emission [124—128] from CO, visible and ultraviolet emission [126] from C2 and C respectively, and vacuum-ultraviolet absorption [128] by CO. 

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