Characterization of composite nanoparticles using an improved light scattering program for coated spheres

The objectives of this paper are twofold. First, the paper developed an improved algorithm to perform light scattering calculations by coated spheres. The improved algorithm was implemented in FORTRAN90 as a subroutine to allow flexible application of the code. Second, the new program was applied to the characterization of composite aluminum nanoparticles. In this application, multiple elements of the Mueller scattering matrix were measured at multiple angles to infer the properties of the nanoparticles, including the size distribution function and the thickness of the coating. The new program played a key role in the fitting of the measured data, and this application demonstrated the advantages of the new program in situations that demand high efficiency and reliability. Program summary: Program title: CMIE. Catalogue identifier: AEFX_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEFX_v1_0.html. Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland. Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html. No. of lines in distributed program, including test data, etc.: 1065. No. of bytes in distributed program, including test data, etc.: 12 933. Distribution format: tar.gz. Programming language: FORTRAN90/95. Computer: Any machine running standard FORTRAN90/95. Operating system: Windows XP (Intel FORTRAN compiler 9.1). RAM: 1-100 Mbyte. Classification: 16.7, 18. Nature of problem: Among various scientific and engineering applications, it is highly desirable to have an efficient, reliable, and flexible program to perform scattering calculations for coated spherical particles. Though several programs are publicly available and can perform such calculations, they are designed for more complicated scatterers (non-spherical, multilayered particles, etc.). As a result, their efficiency and reliability are usually not satisfactory when applied to coated spheres. Therefore, this paper aims at developing an improved program to provide efficient and reliable scattering calculations for coated spheres. Such virtues were demonstrated to be invaluable in applications where scattering calculations need to be performed for a great number of times over a wide range of conditions. Solution method: A new algorithm is developed to directly calculate the pre-factor of the scattering coefficients. This new technique provides reliable calculation of the pre-factor for arbitrarily large size parameters, and offers better control of the termination of the calculation. Based on this algorithm, an improved program was developed to perform light scattering calculations by coated spheres. Restrictions: Only applicable to single scattering, single layer coating, and unity permeability. Running time: Several seconds-several minutes.