Effective Mass of Electron for White Tin

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TL;DR Summary

I want a single representative effective mass for all electrons in tin(white) for a spherical tin nano-particle (for free electron - plasma model).

For some work of mine i need the plasma resonance frequency for tin nanoparticle, i searched various research papers and found different efffective masses tin for different orbits. here i attached screen shot from W A Roger and S B Woods (Cyclotron effective masses in white tin). What value is to be used for effective mass if oscillating electric field could be incident on spherical nanoparticle of tin from any direction?

 

[BigJDubs]

The effective mass for tin nanoparticles is typically determined based on the shape of the nanoparticle. If the nanoparticle is spherical, then the effective mass will usually be determined by the cyclotron effective mass obtained from W A Roger and S B Woods. The value of the effective mass in this case would be 0.2148 m0 (where m0 is the free electron mass). This value should be used when calculating the plasma resonance frequency for a tin nanoparticle.