Mie scattering by a core-shell particle

Explanations

Extinction and scattering spectra for a core-shell particle are calculated using the Mie theory. The core and the shell of the spherical particle are defined by their external radii and compositions (or refractive indices if material n is chosen). The embedding medium is defined by its refractive index. Q_ext, Q_abs and Q_sca are calculated and are respectively the extinction, absorption and scattering cross-sections divided by πR² where R is the external radius of the core-shell sphere.

You can zoom the plot by selecting a rectangle and zoom out using the lower left icon. The plot can also be resized using the lower right icon. The calculated values are available when clicking the DAT icon.

Some optical constants are pre-defined but you can enter your own ones. For example, you can visit refractiveindex.info, choose the material you are interested in and download the data by using the “Full database record” link. Then select the “table” option of the “user-defined” group in the drop-down list for the core or the shell and import the file or paste the data in the text area. Finally select the correct unit for the first column and click the “Apply” button.

Interpolation of the optical constants is accomplished using the monotone cubic interpolation method.

The refractive indices (n and k) may depend on the wavelength l in micrometer. For example, according to doi:10.1364/AO.46.003811 for water at 24°C you may use:
sqrt(1+5.66695982e-1*l*l/(l*l-5.084151894e-3)+1.731900098e-1*l*l/(l*l-1.818488474e-2)+2.095951857e-2*l*l/(l*l-2.625439472e-2)+1.125228406e-1*l*l/(l*l-1.073842352e1))
and according to doi:10.1039/C7NR02952G for PVA you may use:
1.460+0.00665/l/l

References

• Optical constants:
  • Palik : ISBN 978-0-12-544415-6
  • Johnson/Christy : Physical Review B 6, 4370 (1972) and Physical Review B 9, 5056 (1974)
  • Bi : J. Phys. Chem. C 16, 20530, (2012), Si : Solar Energy Materials and Solar Cells 92, 1305 (2008)
• Interpolation of the optical constants using the monotone cubic interpolation method.
• The javascript implementation is adapted from bhcoat by Bohren and Huffman and modified by Bruce T. Draine.
• Complex numbers in javascript : ComplexNumber class by Jan Hartigan
• Sliders to vary the sizes and the refraction index inspired by Julian Kauth.