Assignment of the Terahertz Spectra of Crystalline Copper Sulfate and Its Hydrates via Solid-State Density Functional Theory

Michael Thomas Ruggiero , Tiphaine Bardon , Matija Strlic , Phil F. Taday , and Timothy Michael Korter

Abstract

Terahertz (THz) vibrational spectroscopy is a promising tool for the non-destructive and potentially non-invasive characterization of historical objects, which can provide information on the materials used for their production as well as identify and monitor their chemical degradation. Copper sulfate (CuSO4) has drawn interest due to its inclusion in the preparation of iron gall inks found in historical artwork and documents. Copper sulfate rapidly forms hydrates which contribute to the formulation of these ink species, and may influence their corrosive nature. In this study, copper sulfate has been studied using a combination of THz time-domain spectroscopy, powder X-ray diffraction (PXRD), and solid-state density functional theory (DFT) in order to better understand the spectral absorbances in the THz region. The results have revealed that the THz spectrum of commercially available “anhydrous” copper sulfate results from the presence of not only the anhydrous form, but also the monohydrate (CuSO4⋅H2O) and trihydrate (CuSO4⋅3H2O) forms. Complete assignment of the experimental spectrum was achieved through a comparison of density functionals and extensive investigation of the influence of basis set polarization functions on the bonding interactions, lattice parameters, and low-frequency motions in these crystalline solids.

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://pubs.acs.org/doi/abs/10.1021/jp507927c

Using Terahertz Spectroscopy for Observing the Kinetics of Recrystallisation of Polybutene-1

Journal of Infrared, Millimeter, and Terahertz Waves

February 2013, Volume 34, Issue 2, pp 187-193
doi: 10.1007/s10762-013-9956-8

Authors: V. Křesálek, T. Gavenda
More details at: http://link.springer.com/article/10.1007/s10762-013-9956-8

Abstract

This paper deals with the use of terahertz spectroscopy for observing the kinetics of recrystallisation of polybutene-1 as a suitable material for manufacturing optical elements in the terahertz region of the electromagnetic spectrum. These materials were studied from the perspective of their optical properties – the refractive index and the absorption coefficient. The time dependencies of the refractive index and the absorption coefficient were measured, because polybutene-1 is a material which recrystallises for a number of days from the date of its manufacture. The coefficients describing the recrystallisation process were calculated from the fitting function derived from the Avrami equation. In this paper, the measurement results are presented and the possibilities of the use of the studied materials are discussed.

...Measurement was conducted by a TPS^TM Spectra 3000...Thickness was measured at 12 points of each sample to achieve the desired accuracy, after averaging the measured values. The calculation of the refractive index and absorption coefficient was performed with the TPS^TM Spectra 3000 software, with air as the reference value...

Towards optoelectronic detection of explosives

Opto-Electronics Review, June 2013, Volume 21, Issue 2, pp 210-219

doi 10.2478/s11772-013-0082-x

Authors: J. Wojtas, T. Stacewicz, Z. Bielecki, B. Rutecka, R. Medrzycki, J. Mikolajczyk
More details at: http://link.springer.com/article/10.2478/s11772-013-0082-x

Abstract

Detection of explosives is an important challenge for contemporary science and technology of security systems. We present an application of NOx sensors equipped with concentrator in searching of explosives. The sensors using CRDS with blue — violet diode lasers (410 nm) as well as with QCL lasers (5.26 μm and 4.53 μm) are described. The detection method is based either on reaction of the sensors to the nitrogen oxides emitted by explosives or to NOx produced during thermal decomposition of explosive vapours. For TNT, PETN, RDX, and HMX the detection limit better than 1 ng has been achieved.

... Time domain spectroscopy (TDS) is especially useful in the THz range [12,13]. Observation of explosives' transmission and reflection are conducted by using TeraView TPS Spectra 3000 instrument at the Institute of Optoelectronics, MUT ...

Author Affiliations: Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908, Warsaw, Poland

In 2011 TeraView supplied two TPS Spectra 3000 systems with a stand-off explosives detection module and a fibre-fed scanning system with multiple gantry options for research into terahertz imaging and non-destructive testing. Military University of Technology (MUT) in Poland is one of the country’s most prestigious research institutes for terahertz research and materials characterisation. Read more...