Effects of Scattering on THz Spectra of Granular Solids

  • Aparajita Bandyopadhyay
  • Amartya Sengupta
  • Robert B. Barat
  • Dale E. Gary
  • John F. Federici
  • Minghan Chen
  • David B. Tanner
Article

Abstract

Experimental studies of granular solids have shown that significant scattering effects restrict the accurate determination of material absorption in the terahertz (THz) region. The present work investigates the grain size dependent scattering contribution on the extinction spectra of Ammonium Nitrate, flour and salt between 0.2 to 1.2 THz using THz time-domain spectroscopy. The scattering contribution can be estimated by applying Mie theory for spherical grains. The approach essentially separates the independent contributions of true absorption and scattering losses and thus determines the total extinction for different grain sizes of various materials. The separation of the intrinsic material absorption from scattering losses shows that the frequency dependence in weakly absorbing materials is predominantly particle size dependent. Consequently, that range of THz frequencies cannot be used to differentiate granular solids having no intrinsic absorption.

Keywords

Terahertz Spectroscopy Granular solids Extinction spectra Material identification Mie theory 

Notes

Acknowledgements

AS, AB, RBB, DEG and JFF gratefully acknowledge the funding support of the Technical Support Working Group, the Department of Homeland Security, and the US Army SBIR program. MC and DBT were supported by the NSF Condensed Matter Physics Program through grant DMR-0305043 and the DOE through DE-AI02-03ER46070.

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Aparajita Bandyopadhyay
    • 1
  • Amartya Sengupta
    • 1
    • 4
  • Robert B. Barat
    • 2
  • Dale E. Gary
    • 1
  • John F. Federici
    • 1
  • Minghan Chen
    • 3
  • David B. Tanner
    • 3
  1. 1.Department of PhysicsNew Jersey Institute of TechnologyNewarkUSA
  2. 2.Department of Chemical EngineeringNew Jersey Institute of TechnologyNewarkUSA
  3. 3.Department of PhysicsUniversity of FloridaGainesvilleUSA
  4. 4.Institute of Microwaves and Photonics, School of Electronic and Electrical EngineeringUniversity of LeedsLeedsUK

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