Scattering loss

When the electrons pass from the source volume through the analyser to the detector, they are subject to elastic and inelastic scattering processes. Three effects may result from electron scattering  

It should be noted that a normal line and its accompanying lines due to inelastic energy losses have different dependences on the target density. In the limit of low scattering losses one has 

these different dependences can be used to identify or suppress inelastic scattering effects. 

For quantitative electron spectrometry the most important disturbance caused by scattering processes is the loss of intensity in the registered counting rate /reg as compared to the undisturbed counting rate /0. The effect can be described by a scattering factor fs defined by 

With given values of the total scattering cross section re.scatt and the density distribution nv(x) along the electron s path, the scattering factor /s can be calculated from 

7reg(inel. loss line) = (JVphnv r Az) rinel.nv 7e, 7reg(inel. loss line) 

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The energy threshold appears to be dependent on the excitation spot size at constant pump intensity, which indicates that amplification occurs over the whole illuminated area. It should be stated that, despite the large domains, the optical quality within the domains is lower than that of the annealed films. This gives rise to additional scattering losses which decrease the magnitude of the amplification. 

Transmission IR (TIR) spectroscopy if the solid in question is IR transparent over an appreciable range of wavelength. This is often used on supported metal catalysts, where the large metallic surface area permits a high concentration of adsorbed species to be sampled. The sample consist typically of 10-100 mg of catalyst, pressed into a self-supporting disk of approximately 1 cm2 and a few tenths of a mm in thickness. The support particles should be smaller than the wavelength of the IR radiation, otherwise scattering losses become important. 

Leinse A., Diemeer M.B.J. and Driessen A., Scattering loss reduction in polymer waveguides by reflowing, Electron. Letters 2004 40 992-993. 

Smooth and uniform polymer surface after vacuum plays a key role to ensure good OFRR sensing performance. We have observed in experiments that toluene after vacuum is prone to leave a number of cavities of a few micrometers in diameter on the surface. These cavities will induce additional scattering loss for the WGMs in the OFRR, which greatly degrade the g-factor, and hence the detection limit of the OFRR vapor sensor. Moreover, these small cavities have different adsorption characteristics compared to smooth polymer surface. Vapor molecules may be retained for a longer time at the cavity, which increases the response time and recovery time. Acetone and methanol are found to be better candidates for solvents because they usually leave uniform and smooth surface after vacuum. 

The detection limit of the microresonator-based refractive index sensing device is directly related to the g-factor of the resonator and the sensitivity of the resonant mode discussed above. The g-factor of a microtube resonator is determined by the total loss of a resonant mode, including radiation loss, absorption loss, and surface roughness scattering loss. The overall g-factor can be expressed as... 

Chao, C. Y. Guo, L. J., Reduction of surface scattering loss in polymer microrings using thermal reflow technique, IEEE Photon. Technol. Lett. 2004, 16, 1498 1500... 

Powders give statistically mixed phases and, possibly, spatially unseparated reduction and oxidation sites, as well as poor space charge layers for carrier separation. This leads to high rates of bulk and surface recombination, as well as solution species back reactions. Light scattering losses add a further decrease in... 

F.P. Payne and J.P.R. Lacey, "A theoretical analysis of scattering loss from planar optical waveguides," Opt. Quantum Electron. 26, 977-986 (1994). 

We have successfully demonstrated the concept of simultaneous polymerization and poling of photocrosslinkable systems to produce high quality films with large second-order nonlinear optical susceptibilities and low scattering losses. The ability to process these materials under mild conditions may help avoid potential problems encountered in... 

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