Intensity Of A Spectrum Essay


1.How are the electrons dispersed in the EELS magnetic prism?

2.What function is used to model the background intensity of a spectrum?

3.What function is used in the low-loss region of the spectrum (less then 100eV)?


1.The existence of electromagnetic having a shaped pole pieces results to generation of uniform magnetic field (denoted as B), having an order of approximately 0.01 T .

In this magnetic field produced electrons will follow a circular like paths that is having a radius of R and the electrons will be spontaneously deflected at an angle normally 900.

The force exerted by electrons sideway is

F = B*e *v



e = speed of electron

v = charge

m = mass of electron

The resultant bending radius of electrons that directly depend on the velocity hence electron energy will be equal to;

R =

This clearly demonstrates the bending and dispersion of electrons by EELS magnetic prism

2.typically, the model is determined using linear least-square method using a single pre-edge region ?.


? = background fit window

= signal intgergration window

Ib = background intensity

Ik = signal intensity

Power law formulae is the most common background model for intensity of a spectrum

J( E) = A

A = scaling constant

r = slope exponent ( that is usually 2-6)

3.The EELS in the low energy region less than 100 ev is particularl known as valence electron energy lost spectroscopy. The low loss region determines’

  1. Excitation of valence band electrons
  2. Electronic structure

EEL spectrum at blow loss region can be described in a dielectric formulation as;



v = the speed of the incident region

na = the number of atoms per unit volume

= the characteristic scattering angle (E = E/m0v2)

Im( = the energy loss function

From the equation

The complex dielectric function 1 + 2 is obtained from the low – loss EEL spectrum

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