Attenuation length dependence

The total contribution to the Auger electron signal is then dependent upon the attenuation length (kM) in the matrix before being inelastically scattered, and upon the transmission efficiency of the electron spectrometer as well as the efficiency of the electron detector. Calculated intensities of Auger peaks rarely give an accuracy better than 50%, and it is more reliable to adopt an approach which utilises standards, preferably obtained in the same instrument. 

A neutron will move through material along a straight line with a constant energy until it encounters a nucleus and induces a nuclear reaction. Thus, neutron attenuation follows an exponential law similar to that for photons. Written in terms of an energy-dependent attenuation length, p, we have... 

In this formula A and Aj are the spin-dependent hot electron attenuation lengths, which have been measured by various experimental techniques for different ferromagnetic materials [135-145]. The SVT and MTT have also successfully been used to measure Af and for 3d transition metal alloys [146-148], In these experiments the collector current is measured as a function of the ferromagnetic base layer thickness. 

Figure 19-10. Dependence of yield of LEE-induced 5 -oligonucleotide fragments on their length for electron energies of 8 ( A), 28 (O), and 68 eV ( ). The curves represent decaying exponential fits. The inset shows the dependence of the attenuation length (AL) on LEE energy. The error bars represent the uncertainty range of the fitting parameter in the exponential...

The incident angle of the reflected beam onto the detector is utilized in a factor often described as correcting for the flatness of a detector. The diffracted beam penetrates into the image plate or fluorescent layer of the detector. The penetration length depends on the angle of incidence and the linear attenuation factor for the utilized wavelength and fluorescent material. 

Here, No and N are the numbers of particles at the top of the atmosphere and at the location of the observer, respectively, d is the atmospheric depth (expressed in units of g/cm ), and A is the attenuation length or mean free path (in the same units). A is not a constant but changes with latitude, due to the modification of the cosmic ray energy spectrum depending on the cutoff rigidity, and is also slightly variable with altitude (e.g., Lai 1991). 

Fig. 5.1 Spin resolved intensities of Co/W(110) after excitation with Ne I radiation hv = 16.85 eV). Filled upward triangle denote majority and filled downward triangle minraity electrons. The tungsten structure at a binding energy of 2.9 eV shows significantly different peak areas in both spin channels (light and dark gray shaded) indicating a spin dependence of the particular attenuation lengths...

It seems to be possible to explain the polarization enhancement of secondary electrons by the spin dependence of the IMFP. This means, the different attenuation lengths act as a spin filter, majority electrons preferentially allowing to be transmitted. The spin asymmetry of the IMFP, given by A = (2+ — 2 )/(2+ + 2 ), amounts to about 20% for both systems and is confirmed by an investigation of Fe/Cu(100) [8] leading to the same value of A. A very effective spin filter can be realized by a graphene layer which was theoretically predicted [11] and experimentally verified for graphene on Ni(lll) [12]. 

For a given OF, the attenuation increase depends on the radius of the bend, the number of bends (or length under bend) and the wavelength of the signal (Jay, 2010). As a consequence, when the fibre is bent, the light rays outside of the bent section (sensitive zone) will be emitted, and the others continue to meet the internal reflection. The equation used to calculate the light emission efficiency of a bent POF is given below ... 

Figure 5. Dependence of attenuation length (AL) on the photoelectron kinetic energy for elements, inorganic compounds and organic compounds. (From Ref. 2 based on equations from Ref. 16.)...

As the data are to be defined relative to the C l.v line, all terms in the denominator on the right-hand side may be set to unity. Assuming the energy dependence of the attenuation lengths may be approximated by an exponent p such that ME) Ep and, further, that the energy dependence of the analyzer respon.se function may be represented in a similar manner as Q(E) E i, then Eq. (33) simplifies to... 

An alternative method of deriving relative sensitivity factors would be to use the calculated intensities of. Scofield [40]. after correction for the energy dependences of the attenuation length and analyzer function, as in Eq. (.34). but to use an accurate measure of the full intensity for the experimental data, such as would be obtained from the Tougaard background method (31 ]. A full evaluation of such an approach is not yet available. Preliminary work seems to suggest that the overall results may be more accurate, but possibly with lower precision. That is, there may be benefits in using this method if the analysis is... 

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