Broadband Radiation of Small Dielectric Particles
- PDF / 250,471 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 38 Downloads / 216 Views
CS OF LOW-DIMENSIONAL STRUCTURES, MESOSTRUCTURES, AND METAMATERIALS
Broadband Radiation of Small Dielectric Particles S. Sh. Rekhviashvili* Institute of Applied Mathematics and Automatization, Kabardino-Balkar Scientific Center, Russian Academy of Sciences, Nalchik, 360000 Russia *e-mail: [email protected] Received April 7, 2020; revised April 7, 2020; accepted May 4, 2020
Abstract—A qualitatively new theoretical model of broadband (“white”) thermal radiation of small dielectric particles is proposed. The hypothesis that the high intensity of this radiation can be caused not by extremely high temperature but dielectric properties of the material and/or size effect is stated and justified. The radiation intensity of an absolutely black body and a spherical dielectric particle are calculated depending on the photon gas dimension. Keywords: dielectric particles, thermal radiation, size dependence, similarity dimension, dielectric function DOI: 10.1134/S0030400X20090167
INTRODUCTION In [1–8], the interaction between laser radiation and such dielectric nanomaterials (nanopowders) as oxides and phosphates of rare earth metals was studied. The experiments reveal typical spectra of up-conversion luminescence, as well as continuous spectra which are typical for thermal radiation. The presence of the latter is commonly explained by the fact that the energy of electron transitions leading to luminescence can be efficiently spent for substance heating. Here, however, some contradictions are revealed. Determination of the broadband radiation temperature by comparison of experimental spectra with the Planck distribution yields extremely high temperatures in the interval of 1900–2850 K depending on conditions of the experiment [1–3, 5, 7, 8]. If the sample temperature is estimated in a different way, e.g., using X-ray diffraction [6], it is obtained to be approximately 900 K. This situation is aggravated by two more factors. First, most experiments involved infrared laser diodes which do not develop high power even in the center of the focal spot. Second, it is well known that the melting and evaporation temperatures for small particles decrease from two to four times, which also excludes high heating temperatures of dielectric nanomaterials. At present, there is no common explanation for all these facts. In this work, it is proposed to describe broadband radiation of small dielectric particles using the representation about the size dependence of thermal radiation and the most general model of the Havriliak– Negami dielectric relaxation. The size dependence of absolutely black body radiation was considered in [9– 11]. A generalization of the Planck and Stefan–Boltzmann laws for the n-dimensional space was presented.
It is well known that an absolutely black body in the three-dimensional case is represented as a spherical cavity with mirrored walls. For a two-dimensional absolutely black body, one can take a ring of a thin superconducting wire. Infinitely reflecting from the wire, photons will fill the two-dimensional space inside
Data Loading...
