Scattering by Single Particles General Considerations

In many applications, the most important characteristic of the scattered wave is its intensity, /, expre.ssed in cgs units as erg/cm sec. At large distances from the origin, the energy flowing through a spherical surface element is 7r- sin0 d9 This energy flows radially and depends on 6 and (p but not on r. It is proportional to the intensity of the incident beam In and can be expressed as follows  

The wavelength of the incident beam. is introduced in the denominator to make the scattering function, F 6, p. X), dimensionless. In general, F 0. A.) depends on the 

scattering function can be determined from theory for certain important special cases as discussed in the following sections. The performance of optical single-particle counters (Chapter 6) depends on the variation of the scattering function with angular position, and much effort has been devoted to the design of such detectors. 

The intensity function, by itself, is not suffleient to characterize the scattered light. Needed also are (he polarization and phase of the scattered light, which are discussed in the 

This defines the scattering cross section which has the dimension of area but is not in general equal to the particle cross-sectional area. Indeed it is customary to define the scattering efficiency 

---