The spectroscopy of water vapour: Experiment, theory and applications

Bernath, Peter F.

doi:10.1039/b200372d

Cited by 165 publications

(90 citation statements)

References 184 publications

(233 reference statements)

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“…Water vapour exhibits pure rotational modes of energy transitions spanning the millimetre wave to midinfrared, or approximately 3 GHz-19.5 THz (Kemp et al 1978;Bernath 2002). In the infrared region, both pure rotational line transitions and rotation-vibration bands are noticeable (Gasster et al 1988).…”

Section: Effects Of Water Vapour On Pulsed T-ray Signalsmentioning

confidence: 99%

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

Withayachumnankul

Fischer²,

Mickan³

et al. 2008

Proc. R. Soc. A.

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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 timedomain 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.

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Section: Effects Of Water Vapour On Pulsed T-ray Signalsmentioning

confidence: 99%

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

Withayachumnankul

Fischer²,

Mickan³

et al. 2008

Proc. R. Soc. A.

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“…It is a combination of antisymmetric stretching mode, symmetric stretching mode and an overtone of the bendingmode (Bernath, 2002 ;Tennyson et al, 2014),  the 2360 cm -1 peak corresponds to the atmospheric CO 2 ,…”

Section: Infrared Spectroscopymentioning

confidence: 99%

Physicochemical Characterization of Moroccan Phosphate and Coke of a Solid Combustible

Bouatba

Benchanâa

Hammioui

et al. 2016

IJC

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This paper concerns the study of the phosphate ore and a coke of solid combustible. The determination of their physicochemical characteristics and the study of their structural, textural and morphological aspects before and after thermal treatment are important and necessary for understanding of the reaction mechanisms and of the modelling of the processes of combustion and calcination.The characterization of these materials was accomplished according to various experimental techniques such as: X-ray diffraction; infrared spectroscopy, scanning electron microscopy, porosimetry and the BET method. The results obtained show that the X-ray diffraction pattern of the coke presents only the crystalline phase of the graphite. The diffraction pattern of the raw phosphate as well as the crystallographic parameters at 25°C (a = 9.36 Å, c = 6.90 Å) are consistent with those given in the literature and indeed correspond to those of the crystal lattice of pure fluorapatite. The specific surface of natural phosphate is in the range of 13.36 m² .g -1 and that of the coke is 0.361 m² .g -1 . The total pore volume of the phosphate ore measured by the condensation of nitrogen adsorbed was 0.178 mL and the mean opening diameter of the pores is 0.029 m. The real density of the phosphate (2.96 g.cm -3 ) and that of the coke (1.36 g.cm -3 ), were determined using an ultra pycnometer. Morphological observation of the grain surface shows fairly homogenous areas and a porous structure in the phosphate ore. The coke grains show on the contrary a difference in the grain size and a non-porous structure.

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“…At present, it is one of the few chemically bound polyatomic molecules for which the spectra up to dissociation and above have been observed. An experimental observation of water at dissociation was described as an ultimate goal in a review by Bernath [11]. However, the levels at dissociation are like branches and leaves of a tree, with the root system extending into a conventional study of infrared (IR) and visible spectra.…”

Section: Introductionmentioning

confidence: 99%

Global spectroscopy of the water monomer

Polyansky

Zobov

Mizus

et al. 2012

Phil. Trans. R. Soc. A.

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Given the large energy required for its electronic excitation, the most important properties of the water molecule are governed by its ground potential energy surface (PES). Novel experiments are now able to probe this surface over a very extended energy range, requiring new theoretical procedures for their interpretation. As part of this study, a new, accurate, global spectroscopic-quality PES and a new, accurate, global dipole moment surface are developed. They are used for the computation of the high-resolution spectrum of water up to the first dissociation limit and beyond as well as for the determination of Stark coefficients for high-lying states. The water PES has been determined by combined ab initio and semi-empirical studies. As a first step, a very accurate, global, ab initio PES was determined using the all-electron, internally contracted multi-reference configuration interaction technique together with a large Gaussian basis set. Scalar relativistic energy corrections are also determined in order to move the energy determinations close to the relativistic complete basis set full configuration interaction limit. The electronic energies were computed for a set of about 2500 geometries, covering carefully selected configurations from equilibrium up to dissociation. Nuclear motion computations using this PES reproduce the observed energy levels up to 39 000 cm −1 with an accuracy of better than 10 cm −1 . Line positions and widths of resonant states above dissociation show an agreement with experiment of about 50 cm −1 . An improved semi-empirical PES is produced by fitting the ab initio PES to accurate experimental data, resulting in greatly improved accuracy, with a maximum deviation of about 1 cm −1 for all vibrational band origins. Theoretical results based on this semi-empirical surface are compared with experimental data for energies starting at 27 000 cm −1 , going all the way up to dissociation at about 41 000 cm −1 and a few hundred wavenumbers beyond it.

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The spectroscopy of water vapour: Experiment, theory and applications

Cited by 165 publications

References 184 publications

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

Physicochemical Characterization of Moroccan Phosphate and Coke of a Solid Combustible

Global spectroscopy of the water monomer

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