Polarization orientation dependence of the far infrared spectra of oriented single crystals of 1,3,5-trinitro-S-triazine (RDX) using terahertz time–domain spectroscopy

Abstract

Polarization orientation dependence of the far infrared spectra of oriented single crystals of 1,3,5,-trinitro-s-triazine (RDX) using terahertz time-domain spectroscopy. Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under contract DE-ACS2-06NA2S396. By acceptance of this article, the publisher recognizes that the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. AbstractThe far infrared spectra of (100), (010), and (001) oriented RDX single-crystals were measured as the crystal was rotated about the axis perpendicular to the polarization plane of the incident radiation.Absorption measurements were taken at temperatures of both 20 K and 295 K for all rotations using terahertz time-domain spectroscopy. A number of discrete absorptions were found ranging from 10 100 cm-1 (0.3-3 THz) . The absorptions are highly dependent on the orientation of the terahertz polarization with respect to crystallographic axes.

High Resolution Waveguide Terahertz Time-Domain Spectroscopy

“…In addition, the thickness of the crystal has to be carefully adjusted to allow transmission over a broad band of frequencies. Examples of THz-TDS of single-crystal samples may be found in references [51] and [52]. It was found that relatively simple film preparation methods such as casting from solution and vacuum sublimation can produce films of sufficient crystallinity to begin to resolve their complex THz spectra [53].…”

A Review on Thin-film Sensing with Terahertz Waves

“…A similar problem should be expected of any anisotropic sample unless there is determined some way to deliberately orient the sample within the waveguide. This remains a standing issue in the terahertz characterization of explosives [78,79]. The composition of the waveguide plates can also affect the measurement.…”

Recent Advances in Birefringence Studies at THz Frequencies

“…Different crystals, such as quartz [31], sapphire [31,34], lithium niobate (LiNbO 3 ) [34][35][36], rutile [2], β-BaB 2 O 4 (BBO) [37,38], zinc oxide [39], the explosive 1,3,5-trinitro-S-triazine (RDX) [40], but also the organic crystal dimethyl amino 4-N-methylstilbazolium tosylate (DAST) Fig. 1 Refractive index ellipsoid of a uniaxial, positively birefringent material [41] or molecular oxalic acid crystals [42] have shown to exhibit THz birefringence.…”

“…One frequently pursued approach for the determination of the optical axis is the measurement at different azimuthal angles by rotating the sample. Examples are given, e.g., in [34,[39][40][41][42], where the sample was rotated stepwise and a single polarization component was detected at each angular position. The extremes of the resulting time-domain curves as a function of the rotation angle allow an identification of the orientation of the optical axis, and the corresponding time-domain signals can be used for a direct evaluation of Δn [34,39] analogous to Chap.…”