scholarly journals Terahertz Rotational Spectroscopy of Greenhouse Gases Using Long Interaction Path-Lengths

2021 ◽  
Vol 11 (3) ◽  
pp. 1229
Author(s):  
Arnaud Cuisset ◽  
Francis Hindle ◽  
Gaël Mouret ◽  
Robin Bocquet ◽  
Jonas Bruckhuisen ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Thz Spectroscopy ◽  
Rotational Spectroscopy ◽  
Line Intensities ◽  
Quantitative Measurements ◽  
Fabry Perot ◽  
Laboratory Investigations ◽  
Rotational Transitions ◽  
Path Lengths ◽  
Thz Absorption

Even if on-board mm-wave/THz heterodyne receivers have been developed to measure greenhouse gases (GHGs) atmospheric profiles, rotational spectroscopy rests under-exploited for their monitoring unlike IR rovibrational spectroscopy. The present study deals with the ability of THz spectroscopy using long interaction path-lengths for GHG laboratory investigations. High-resolution THz signatures of non-polar greenhouse molecules may be observed by probing very weak centrifugal distortion induced rotational transitions. To illustrate, new measurements on CH4 and CF4 have been carried out. For CH4, pure rotational transitions, recorded by cw-THz photomixing up to 2.6 THz in a White type cell adjusted to 20 m, have allowed to update the methane line list of atmospheric databases. Concerning CF4, Fabry-Perot THz absorption spectroscopy with a km effective pathlength was required to detect line intensities lower than 10−27 cm−1/(moleccm−2). Contrary to previous synchrotron-based FT-FIR measurements, the tetrahedral splitting of CF4 THz lines is fully resolved. Finally, quantitative measurements of N2O and O3 gas traces have been performed in an atmospheric simulation chamber using a submm-wave amplified multiplier chain coupled to a Chernin type multi-pass cell on a 200 m path-length. The THz monitoring of these two polar GHGs at tropospheric and stratospheric concentrations may be now considered.

scholarly journals Temperature dependent poly(L-lactide) crystallization investigated by Fourier transform terahertz spectroscopy

2021 ◽  
Author(s):  
Seiichiro Ariyoshi ◽  
Satoshi Ohnishi ◽  
Hikaru Mikami ◽  
Hideto Tsuji ◽  
Yuki Arakawa ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Absorption Spectra ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Thz Absorption

Poly(L-lactide) (PLLA) was investigated by Fourier transform terahertz (THz) spectroscopy over the frequency range of 1.0 – 8.5 THz. THz absorption spectra were acquired for PLLA samples isothermally crystallized at...

scholarly journals Calculated Terahertz Spectra of Glycine Oligopeptide Solutions Confined in Carbon Nanotubes

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 385 ◽  
Author(s):  
Dongxiong Ling ◽  
Mingkun Zhang ◽  
Jianxun Song ◽  
Dongshan Wei
Keyword(s):  
Carbon Nanotubes ◽  
Signal To Noise Ratio ◽  
Thz Spectroscopy ◽  
Water Molecules ◽  
Relaxation Dynamics ◽  
Confinement Effects ◽  
Nanofluidic Channels ◽  
Detection Of Biomolecules ◽  
Thz Absorption ◽  
Dynamics Simulations

To reduce the intense terahertz (THz) wave absorption of water and increase the signal-to-noise ratio, the THz spectroscopy detection of biomolecules usually operates using the nanofluidic channel technologies in practice. The effects of confinement due to the existence of nanofluidic channels on the conformation and dynamics of biomolecules are well known. However, studies of confinement effects on the THz spectra of biomolecules are still not clear. In this work, extensive all-atom molecular dynamics simulations are performed to investigate the THz spectra of the glycine oligopeptide solutions in free and confined environments. THz spectra of the oligopeptide solutions confined in carbon nanotubes (CNTs) with different radii are calculated and compared. Results indicate that with the increase of the degree of confinement (the reverse of the radius of CNT), the THz absorption coefficient decreases monotonically. By analyzing the diffusion coefficient and dielectric relaxation dynamics, the hydrogen bond life, and the vibration density of the state of the water molecules in free solution and in CNTs, we conclude that the confinement effects on the THz spectra of biomolecule solutions are mainly to slow down the dynamics of water molecules and hence to reduce the THz absorption of the whole solution in confined environments.

High-Precision Continuous-Wave Terahertz Spectroscopy Based on a Photomixing Technique for Identifying Pearls

2019 ◽  
Vol 73 (12) ◽  
pp. 1388-1393
Author(s):  
Chihoon Kim ◽  
Taeksoo Ji
Keyword(s):  
Optical Coherence Tomography ◽  
Fourier Transform ◽  
Ir Spectroscopy ◽  
Continuous Wave ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Ft Ir ◽  
Thz Absorption ◽  
Ft Ir Spectroscopy ◽  
Cultured Pearls

We present the accurate terahertz spectra of between imitation and cultured pearls using continuous-wave terahertz (CW-THz) spectroscopy. Using Fourier transform infrared (FT-IR) spectroscopy and optical coherence tomography (OCT) measurements, cultured pearls can be distinguished from imitation pearls by observing distinct absorption peaks and discriminative boundaries. The THz absorption spectra up to 0.3 THz obtained from CW-THz spectroscopy show several absorption peaks at specific frequencies with the cultured pearls but no peaks with the imitation pearls, which results from the existence of the nacre polymorph of cultured pearls. Hence, it is expected that the CW-THz system proposed herein will be applicable to fast, nondestructive spectrum analysis including pearl identification.

DEVELOPMENT OF COMPUTATIONAL METHODOLOGIES FOR THE PREDICTION AND ANALYSIS OF SOLID-STATE TERAHERTZ SPECTRA

2007 ◽  
Vol 17 (02) ◽  
pp. 193-212 ◽  
Author(s):  
Damian G. Allis ◽  
Timothy M. Korter
Keyword(s):  
Solid State ◽  
Density Functional ◽  
State Density ◽  
Grid Size ◽  
Basis Set ◽  
Detection Methods ◽  
Thz Spectroscopy ◽  
Atomic Charges ◽  
Spectral Features ◽  
Thz Absorption

The analytical applications of terahertz (THz) spectroscopy for the characterization of molecular solids have been limited by the lack of information concerning the assignment of observed spectral features to specific internal (intramolecular) and external (intermolecular) atomic motions. Computational methodologies addressing the assignment of spectral data are the enabling technology for moving THz spectroscopy to the forefront of available detection methods for both imaging and spectroscopic applications. Solid-state density functional theory (DFT) studies have been performed on the high explosives cyclotetramethylenetetranitramine (HMX) and pentaerythritol tetranitrate (PETN) in order to address the dependencies of the predictions of solid-state vibrations in the terahertz (3 to 120 cm−1) region on the choice of basis set and integration grid size, building on previous work that examined this dependency on the choice of density functional. DFT THz simulations reveal that both the choice of basis set and grid size have important influences on the reproduction of spectral features. The sensitivity to basis set choice is most pronounced in the calculation of vibrational intensities, where it is found that THz absorption intensities are most accurately reproduced when derived from basis set-sensitive Mulliken atomic charges as opposed to basis set-insensitive atomic charges generated by the Hirshfeld partitioning method.

Design of an X-Ray Fluorescence Sensor for the Cone Penetrometer

1994 ◽  
Vol 38 ◽  
pp. 699-704
Author(s):  
W.T. Elam ◽  
J. Y. Gilfrich
Keyword(s):  
Detection Limits ◽  
Correction Method ◽  
Cone Penetrometer ◽  
X Ray ◽  
Fundamental Parameters ◽  
Quantitative Measurements ◽  
Regulatory Limits ◽  
Path Lengths ◽  
Ray Path ◽  
Certified Values

Abstract The cone penetrometer is a well-established method for exploring soil types whereby a smalldiameter pipe with a hardened cone tip is pushed hydraulically into the ground. The system can be equipped with sensors to detect soil contamination. We have investigated the development of an x-ray fluorescence (XRF) sensor to be deployed via this system. The principal uncertainties in the application of XRF to metals detection in the cone penetrometer are the detection limits and the accuracy of a sensor built in such a confined geometry. A laboratory mock-up was constructed to investigate the performance of such a sensor. An x-ray tube operated at very low power was coupled to an electrically cooled Si(Li) detector. The x-ray path lengths were kept short and an aperture and incident x-ray filter similar to those appropriate for a penetrometer sensor were used. Spectra were collected on a series of Standard Reference Material soils from the National Institute of Standards and Technology consisting of soils with various levels of metal contamination. The detection limits were determined for the metals present in the soils and were comparable to the solid waste regulatory limits. Quantitative measurements were compared to the NIST certified values both without matrix correction and using the fundamental parameters correction method. Results were generally within 10% of the certified values.

scholarly journals Sub-Hz Differential Rotational Spectroscopy of Enantiomers

Symmetry ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 28
Author(s):  
Lincoln Satterthwaite ◽  
Greta Koumarianou ◽  
Daniel Sorensen ◽  
David Patterson
Keyword(s):  
Parity Violation ◽  
Rotational Spectroscopy ◽  
Buffer Gas ◽  
Structural Effects ◽  
Gas Cell ◽  
Pulsed Jet ◽  
Fabry Perot ◽  
Systematic Effects ◽  
First Time ◽  
Opening Up

We demonstrate for the first time high-precision differential microwave spectroscopy, achieving sub-Hz precision by coupling a cryogenic buffer gas cell with a tunable microwave Fabry–Perot cavity. We report statistically limited sub-Hz precision of (0.08 ± 0.72) Hz, observed between enantiopure samples of (R)-1,2-propanediol and (S)-1,2-propanediol at frequencies near 15 GHz. We confirm highly repeatable spectroscopic measurements compared to traditional pulsed-jet methods, opening up new capabilities in probing subtle molecular structural effects at the 10−10 level and providing a platform for exploring sources of systematic error in parity-violation searches. We discuss dominant systematic effects at this level and propose possible extensions of the technique for higher precision.

Propanal, an interstellar aldehyde – first infrared band strengths and other properties of the amorphous and crystalline forms

2020 ◽  
Vol 494 (4) ◽  
pp. 4606-4615
Author(s):  
Yuki Y Yarnall ◽  
Perry A Gerakines ◽  
Reggie L Hudson
Keyword(s):  
Observational Studies ◽  
Solid Phase ◽  
Molecular Ions ◽  
Infrared Band ◽  
Benchmark Data ◽  
Quantitative Measurements ◽  
Theoretical Investigations ◽  
Laboratory Investigations ◽  
Formation And Evolution ◽  
Crystalline Forms

ABSTRACT Chemical evolution in molecular clouds in the interstellar medium is well established, with the identification of over 200 molecules and molecular ions. Among the classes of interstellar organic compounds found are the aldehydes. However, laboratory work on the aldehydes has scarcely kept pace with astronomical discoveries as little quantitative solid-phase infrared (IR) data have been published on any of the aldehydes, and the same is true for important properties such as density, refractive indices, and vapour pressures. In this paper, we examine the IR spectra of solid propanal (HC(O)CH2CH3, propionaldehyde), along with several physical properties, for both the amorphous and crystalline forms of the compound. The quantitative measurements we report, such as IR intensities and optical constants, will be useful in laboratory investigations of the formation and evolution of propanal-containing ices, will serve as benchmark data for theoretical investigations, and will inform observational studies.

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