BSA Flow Software Installation and User's Guide - CSI

Table of characteristic angles
Definitions
In addition, it is important to avoid the interference with third order
refraction, i.e. either select a scattering angle of minimum 4° to 5° above ϕ r3 ,
or at least about 15° below this angle. This means that you must consider
the range of relative refractive index.
Figure 7-49 illustrates as an example the situation where n rel may vary
between 1.334 and 1.46. It is seen here that the rainbow angle of third order
refraction sweeps almost the entire sector between the greatest value of ϕ c1
and the smallest value of ϕ r , rendering only one useful angle.
Figure 7-49: Intensity charts representing two relative refractive indices,
1.46 (A) and 1.334 (B), determining the lower and upper bounds to the
useful range of scattering angles.
The following table is the basis for Figure 7-37: It can be used as a tool for
selecting the scattering angle.
• D min
The minimum particle diameter to be measured (µm).
• n1 The index of refraction of the particle.
• n2 The index of refraction of the external medium.
• nrel The relative index of refraction = n1/n2.
• b0 Brewster’s angle for external reflection. This is the angle at
which reflection is zero for polarization parallel to the scattering plane.
• b2 Brewster’s angle for internal reflection. This is the angle at
which reflection is zero for polarization parallel to the scattering plane.
• c1 The critical angle for refraction. This is the maximum
scattering angle for first order refraction.
• c2 The critical angle for second order refraction. For nrel < 1, c2
= c1.
• r2 The rainbow angle for second order refraction.
r3 The rainbow angle for third order refraction.
BSA Flow Software:Reference guide 7-55