BSA Flow Software Installation and User's Guide - CSI

Figure 7-33: The definitions of the modes of scattering.
All three modes of scattering can be used with the PDA. There is, however,
one crucial point which is imperative to be kept in mind. The PDA estimates
the particle size from the phase differences of the Doppler bursts received by
the different photo-detectors in the receiving optics. Since the three modes
of scattering give rise to different conversion factors (phase factors),
receiving light from more than one scattering mode is likely to give rise to
errors.
Note Therefore, you should always set up a PDA system so that only one mode of
scattering dominates the light received by the receiving optics.
Various modes of scattering dominate the scattered light at different
scattering angles. This we shall take into account when choosing the
scattering angle. In addition, the angular dependence of the intensity of each
scattering mode also differs with the polarization orientation of the scattered
light, which also can be used to discriminate between the different modes.
Scattering angles The angles of the reflected, refracted and second order refracted rays (Figure
7-34) can be expressed in terms of the angle of incidence, ϕ i , and the relative
refractive index n rel .
Figure 7-34: Ray tracing illustrating the angles ϕi, ϕ0, ϕ1
and
For reflection:
ϕ0= π−2ϕi For refraction:
ϕ
ϕ1
ϕ
=
⎡ ⎛ ⎞ ⎤
2 ⎢arcsin⎜
⎟ − ⎥
⎣⎢
⎝ ⎠ ⎦⎥
sin i
i
nrel
For second order refraction:
(A1-10)
(A1-11)
7-38 BSA Flow Software: Reference guide
ϕ 2 .