Electron emission kinetics

Fluorescent chemical sensors occupy nowadays a prominent place among the optical devices due to its superb sensitivity (just a single photon sometimes suffices for quantifying luminescence compared to detecting the intensity difference between two beams of light in absorption techniques), combined with the required selectivity that photo- or chemi-luminescence impart to the electronic excitation. This is due to the fact that the excitation and emission wavelengths can be selected from those of the absorption and luminescence bands of the luminophore molecule in addition, the emission kinetics and anisotropy features of the latter add specificity to luminescent measurements8 10. 

The kinetic energies (KEs) of the photoelectrons are measured by the use of a modification of a conventional p-ray spectrometer as used in the study of p-particle (electron) emissions from radioactive nuclei. The... 

The electron- and hole-trapping dynamics in the case of WS2 are elucidated by electron-quenching studies, specifically by the comparison of polarized emission kinetics in the presence and absence of an adsorbed electron acceptor, 2,2 -bipyridine [68]. In the absence of an electron acceptor, WS exhibits emission decay kinetics similar to those observed in the M0S2 case. The polarized emission decays with 28-ps, 330-ps, and about 3-ns components. For carrier-quenching studies to resolve the dynamics of electron trapping, it is necessary that the electron acceptor quenches only conduction-band (not trapped) electrons. It is therefore first necessary to determine that electron transfer occurs only from the conduction band. The decay of the unpolarized emission (when both the electron and the hole are trapped) is unaffected by the presence of the 2,2 -bipyridine, indicating that electron transfer docs not take place from trap states in the WS2 case. Comparison of the polarized emission kinetics in the presence and absence of the electron acceptor indicates that electron transfer does occur from the conduction band. Specifically, this comparison reveals that the presence of 2,2 -bipyridine significantly shortens the slower decay component of the polarized... 

Electron transfer kinetics from the triplet excited state of TMPD to PA in polystyrene has been monitored by phosphorescence emission decay in ref. 85. The rate constant has been found to be invariant over the temperature interval 77-143 K. Parameters ae and ve calculated from the phosphorescence decay using eqn. (12) were found to be ae = 3.46 A and vc = 104 s 1. 

Fig. 1. Comparison of the four different physical processes which can be observed during the interaction of X-ray photons with matter 2 1. The two phenomena scetched below, namely photoelectron emission and Auger electron emission, can be detected and measured in a photoelectron spectrometer by determining the kinetic energy of the ejected free electrons...

In Ref. [68], the character of the electronic decay dynamics in a multiply charged system was investigated by constructing a simple but realistic model based on the Li-L2/3M CK decay in Ar (see Ref. [69] and references therein). Due to the relatively low energy of the recombination transition within a single shell, CK processes are characterized by the emission of relatively slow electrons with kinetic energies of the order of several tens of electron volt. This circumstance makes CK decay processes in general and the Ar decay in particular very well suited for the study of the effect... 

Here the quantity U is an effective potential that contains three contributions the kinetic energy for the radial movement of the electrons (in the coordinate a), a centrifugal potential energy, and the Coulomb potential energy — C(a, 12)/R of the system. In the present context of double photoionization it is this Coulomb energy which determines the features of two-electron emission (in atomic units) ... 

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