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https://hdl.handle.net/2440/51815
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Type: | Journal article |
Title: | Numerical removal of water-vapour effects from THz-TDS measurements |
Author: | Withayachumnankul, W. Fischer, B. Abbott, D. |
Citation: | Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2008; 464(2097):2435-2456 |
Publisher: | Royal Soc London |
Issue Date: | 2008 |
ISSN: | 1364-5021 1471-2946 |
Statement of Responsibility: | Withawat Withayachumnankul, Bernd M Fischer and Derek Abbott |
Abstract: | The use of T-rays, or terahertz radiation, to identify substances by their spectroscopic fingerprints is a rapidly moving field. The dominant approach is presently terahertz time-domain spectroscopy. However, a key problem is that ambient water vapour is ubiquitous and the consequent water absorption distorts the T-ray pulses. Water molecules in the gas phase selectively absorb incident T-rays at discrete frequencies corresponding to their molecular rotational transitions. When T-rays propagate through an atmosphere, this results in prominent resonances spread over the T-ray spectrum; furthermore, in the time domain, fluctuations after the main pulse are observed in the T-ray signal. These effects are generally undesired, since they may mask critical spectroscopic data. So, ambient water vapour is commonly removed from the T-ray path by using a closed chamber during the measurement. Yet, in some applications, a closed chamber is not always feasible. This situation, therefore, motivates the need for an optional alternative method for reducing these unwanted artefacts. This paper represents a study on a computational means that is a step towards addressing the problem arising from water vapour absorption over a moderate propagation distance. Initially, the complex frequency response of water vapour is modelled from a spectroscopic catalogue. Using a deconvolution technique, together with fine tuning of the strength of each resonance, parts of the water vapour response are removed from a measured T-ray signal, with minimal signal distortion, thus providing experimental validation of the technique. © 2008 The Royal Society. |
DOI: | 10.1098/rspa.2007.0294 |
Published version: | http://dx.doi.org/10.1098/rspa.2007.0294 |
Appears in Collections: | Aurora harvest Electrical and Electronic Engineering publications |
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