BSA Flow Software Installation and User's Guide - CSI

Using side scatter (reflected light) is therefore uncomplicated when this is
the only scattering mode, i.e. in the unshaded area corresponding to the
range 1 < n rel < 2 at scattering angles above the critical angle (ϕ c1 ) for
refraction (continuous line), and below the rainbow angle for second order
refraction (dashed) and the critical angle for second order refraction
(dashed). In addition, one should avoid the rainbow angle for second order
refraction and the range close below this angle.
For n rel < 1, scattering angles just below the critical angle for refraction
(continuous line) should be chosen to avoid contributions from refracted
light while maintaining light intensity.
Also, when n rel > 2 you should choose scattering angles greater than ϕ c1
and, when possible, use parallel polarization in conjunction with ϕ b2 to
avoid contributions from second order refraction.
Refraction Refraction exists at scattering angles below the critical angle (fill patterns
comprising horizontal lines and horizontal-vertical cross-hatching, and
limited by continuous line). Using forward scatter is the best for n rel > 1.27,
where the optimum scattering angle is ϕ b1 , the Brewster condition (dash-dot)
in combination with parallel polarization to avoid contribution from reflected
light.
Second order Second order refraction exists for n rel > 1 at scattering angles above the
refraction rainbow angle or above the critical angle for second order refraction. In the
regions represented by light vertical lines, this mode has only a single
contribution. Using back scatter is often complicated by the emitted light
rays in a given direction emerging at different locations of the particle
surface, thus giving two contributions (horizontal-vertical cross-hatching for
n rel < 1, or medium vertical lines) or three contributions (heavy vertical
lines).
Third order
Using light from such regions is likely to cause non-linearities in the
diameter–phase relationship. To avoid this it is preferable to choose regions
of the chart where the rays in a given direction stem from (or at least are
dominated by) only one incident ray. This would be the case at scattering
angles higher than the critical angle ϕ c2 , and at relative refractive index
above about 1.5 below the rainbow angle. Most often the best results are
obtained with perpendicular polarization to avoid the Brewster effect around
ϕ b2 .
For n rel < 1 this mode of scattering exists at all angles.
In the range 0 to ϕ c2 = ϕ c0 (corresponding to the range of first order of
diffraction), there are two contributions.
Third order refraction (dotted area) normally carries little enough light
BSA Flow Software:Reference guide 7-43