Expanding scattered field into series of spherical harmonics

[GoogleCodeExporter]

Currently ADDA calculates the scattered intensity for a set of scattering 
angles. In certain applications, scattering function is described as a series 
of spherical harmonics. Thus, simulation method should provide the 
corresponding coefficients. The straightforward way is to calculate the 
scattering intensity for a large set of scattering angles and then obtain 
coefficients by simple numerical integration. 

However, a more direct approach is also possible. Radiation of each dipole is a 
trivial spherical harmonics itself. Hence, the problem transforms into 
translation of spherical-harmonics expansion to a different origin. For this 
problem, efficient algorithms have already been developed for multiple-sphere 
T-matrix codes.

Solution of this issue may also help with issue 103.

Original issue reported on code.google.com by yurkin on 21 Dec 2011 at 9:41

• Blocking: Improve integration of Mueller matrix over phi (azimuthal angle) #154, Calculation of the T-matrix using the DDA #103, Optimize calculation of Csca and g  #22, Optimize scattered fields for large grid of angles #51, Enhance orientation averaging #11