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;
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’
- Excitation of valence band electrons
- 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
E = 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