Article

International Journal of Infrared and Millimeter Waves

, Volume 28, Issue 11, pp 969-978

First online:

Effects of Scattering on THz Spectra of Granular Solids

  • Aparajita BandyopadhyayAffiliated withDepartment of Physics, New Jersey Institute of Technology
  • , Amartya SenguptaAffiliated withDepartment of Physics, New Jersey Institute of TechnologyInstitute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds Email author 
  • , Robert B. BaratAffiliated withDepartment of Chemical Engineering, New Jersey Institute of Technology
  • , Dale E. GaryAffiliated withDepartment of Physics, New Jersey Institute of Technology
  • , John F. FedericiAffiliated withDepartment of Physics, New Jersey Institute of Technology
  • , Minghan ChenAffiliated withDepartment of Physics, University of Florida
  • , David B. TannerAffiliated withDepartment of Physics, University of Florida

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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