Recombination radiation

Fig. 3.30 is believed to be in the Sedov phase, with the shock propagating at a high velocity (730 km s-1) in the rarefied intercloud ISM ( h 0.9 cm-3) and at a much slower velocity (< 140 km s-1) in nearby dense molecular clouds (nu 150 cm-3) where it gives rise to optical and UV emission. The X-ray continuum is a sum of recombination radiation from various ions plus thermal bremsstrahlung, aka free-free emission, the latter being given for an ion with charge Ze by... 

W Helfrich and WG Schneider, Recombination radiation in anthracene crystals, Phys. Rev. Lett., 14 229-231, 1965. 

There are two types of mechanisms for the CTL emission. One is the recombination radiation (Sect. 3.1) and the other is radiation from the excited species (Sect. 3.2). 

Phosphors doped with rare-earth elements show two types of CTL spectrum, namely emission from the excited species and recombination radiation, simultaneously. Figure 21 shows the CTL spectrum from the TL-phosphor BaS04 Eu in air containing ethanol vapor. The emission band with fine spectrum components at 420 nm is attributed to the excited HCHO. The line spectrum components peaking at 580 and 615 nm are attributed to the electronic transitions within Eu3+ ions. 

The elementary working mechanism of the CTL-based gas sensor is summarized as follows In air containing combustible gases, the catalytic oxidation proceeds on the heated solid catalyst. Two CTL processes proceed during the reaction. One is production of the excited species, e.g. formaldehyde, followed by its relaxation radiation. The other is the recombination radiation of carriers originating from the surface states formed by the chemisorbed species... 

Figure 26 Emission spectra (PL, EL) in PC at room temperature of 40 wt% TPD donor solution with a 40 wt% of PBD acceptor added. The photoluminescence (PL) spectrum excited at 360 nm, the electroluminescence (EL) spectra (I, II) originate from the recombination radiation in a 60 nm thick film, taken at two different voltages. Absorption (Abs) and PL spectra (excitation at 360 nm) of (75wt% TPD 25wt% PC) and (75wt% PBD 25wt% PC) spin-cast films are given for comparison. Molecular structures of the compounds used are given in the upper part of the figure TPD [N,Nf-diphenyl-A v/V/-bis(3-methylphenyl)-l,l -biphenyl-4,4 diamine PBD [2-(4-biphenyl)-5-(4- er .-butylphenyl)l,3,4-oxadiazole PC[bisphe-nol-A-polycarbonate]. Adapted from Ref. 112.

The spatial distribution of emitting species produced in the electron-hole recombination process is one of important reasons for a difference between the PL and EL spectra, and a characteristic determining the EL quantum efficiency. The self-absorption of the short-wavelength part of the fluorescence can be utilized for determining the spatial distribution of EL. The principle of the method, as discussed in Sec. 3.1 and used for photoexcited states in Sec. 3.2, has been adapted to the recombination radiation as follows [41] the unknown spatial distribution of the EL light intensity, if/ x) from a plate-shaped emitting sample, is related to the experimentally observed EL signal, El(Zo), by the expression... 

Apart from the fact that some of the analyte elements were not detected at their normal concentration levels in urine, the main feature of the analytical results was their overall consistency. The results from the method of additions agreed well with those from the calibration approach and, in either case, the results obtained for the dilute, normal, and concentrated sample solutions also were in good agreement with each other. With the exception of arsenic and titanium, the results for the two methods and for the three urine concentrations were within one detection-limit concentration of each other for all of the elements. Although it has been noted (25) that detection-limit values are "inherently imprecise numbers and that detection-limit concentrations "can only be detected,. . . , and not measured quantitatively, the consistency of the analytical results indicates that the backgroimd correction scheme was effective for elimination of the eflFects of stray light and recombination radiation. As noted earlier, the ratios of net analyte line to net internal reference line intensities were used to decrease the eflFects of sample-to-sample variations in total dissolved solids content. 

Helfiich W. and Schneider W. G., Recombination Radiation in Anthracene Crystals, Phys. Rev. Lett. 14, (1965) 229... 

Can we estimate the density of localized gap states Their presence is noticed in measurements for instance of drift mobility, photoconduction, (Arnoldussen, Bube, Fagen and Holmberg (1972a, b)Weiser(1972)), thermo-stimulated currents (Kolomiets and Mazets (1970)), recombination radiation (Kolomiets, Mamontova, and Babaev (1970)), and high field conduction. A density of gap states cannot be obtained from these experiments though, without having values for the appropriate trapping and recombination cross sections. 

Fig. 5.63a,b. Schematic level diagram of a semiconductor diode (a) unbiased p-n junction and (b) inversion in the zone around the p-n junction and recombination radiation when a forward voltage is applied... 

Recombination radiation In addition to Bremsstrahlung radiation, a hot plasma also emits recombination radiation. This radiation is emitted when a free electron is captured in a bound state of an ion. If E is the kinetic energy of a free electron and Xn is the ionization potential of the energy level in which the electron is captured, the radiation is emitted with a photon energy oihv = E + (Figure 9). As the free... 

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