Water Isotopologues Research Articles

Water vapor stable isotope memory effects of common tubing materials

Abstract. Water molecules in vapor can exchange with gaseous water molecules sticking to surfaces of sampling tubing, and exchange rates are unique for each water isotopologue and tubing material. Therefore, water molecules on tubing walls take some time to reach isotopic equilibrium with a new vapor isotopic signal. This creates a memory effect that is observed as attenuation time for signal propagation in continuous stable water vapor isotope measurement systems. Tubing memory effects in δD and δ18O measurements can limit the ability to observe fast changes, and because δD and δ18O memory are not identical, this introduces transient deuterium excess (D-excess, defined as δD-8×δ18O) artifacts in time-varying observations. To our knowledge, a comprehensive performance comparison of commonly used tubing material water exchange properties in laser-based measurement systems has not been published. We compared how a large isotopic step change propagated through five commonly used tubing materials for water isotopic studies – perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), high-density polyethylene (HDPE), and copper – at two different temperatures and an airflow rate of 0.635 L min−1 through approximately 100 ft (30.5 m) of 1/4 in. (6.4 mm) outer diameter (o.d.) tubing. All commonly used tubing materials performed similarly to each other in terms of attenuation times, reaching δ18O-location-adjusted δD and δ18O 95 % completion in less than 45 s, with slight variations based on temperature. PFA does appear to perform slightly better than the other materials, although memory metric differences are small. A tubing material commonly used in the early 2000s but reported to have memory effects on δD, Dekabon, was also tested at ambient temperature and changing humidities. The Dekabon isotopic equilibrium was not reached until nearly an hour after source transition, much later than H2O mixing ratios equilibrated. Bev-A-Line XX (used in some soil O2 and CO2 gas studies) was also tested at ambient temperature, but it did not approach isotopic equilibrium until after nearly 6 h of testing. Therefore, we cannot recommend the use of Bev-A-Line XX or Dekabon in water vapor isotope applications. Source transition from heavy to light or from light to heavy affected isotopic transition speed only in experiments where H2O ppmv was changing. While a shorter tubing lengths and smaller inner diameters shorten the delay of signal propagation through the tubing, they did not greatly change the attenuation curves under these conditions for the current commonly used tubing materials tested. However, in Dekabon, attenuation curves were greatly extended with increased tubing length. Our results show that the commonly used plastic tubing materials tested were not inferior to copper in terms of isotopic memory under these conditions, and they are easier to work with and are less expensive than copper.

Features of IR Spectra of Olivines Containing Isotopologues of Water

Features of IR Spectra of Olivines Containing Isotopologues of Water

Heavy Water Microdroplet Surface Enriches the Lighter Isotopologue Impurities.

Water microdroplets promote unusual chemical reactions at the air-water interface. However, the interfacial structure of water microdroplets and its potential influence on chemical processes are still enigmatic. Here, we present evidence of in-droplet fractionation of water isotopologues. Employing a sonic spray, we atomized the heavy water (D2O, 99.9 atom % D) solution of three classes of organic compounds (basic, acidic, and neutral). The analytes were predominantly desorbed from the resulting droplet surface in protonated form rather than deuterated form, as detected by mass spectrometry. This result remained unaltered upon adding formic acid-d2 (DCOOD) to the droplet. Monitoring Dakin oxidation of benzaldehyde at the surface of binary microdroplets composed of 1:1 (v/v) D2O/H218O revealed the preferred formation of phenolate-16O over phenolate-18O. Atmospheric pressure chemical ionization mass spectrometric analysis of the vapor composition in the sprayed aerosol revealed the preferential evaporation of lighter water isotopologue impurities from the surface of heavy water microdroplets. These results indicate the enrichment of lighter water isotopologue impurities (HOD/H2O) on the surface of heavy water microdroplets, implying possible future developments for water isotopologue fractionation using microdroplets.

The far infrared absorption spectrum of D216O, D217O, and D218O: Experimental line positions, empirical energy levels and recommended line lists

The far infrared absorption spectra of D216O, D217O, and D218O are analyzed with improved accuracy and sensitivity in the 50–720 cm−1 range corresponding to the rotational band. Four room-temperature absorption spectra of highly deuterated water vapor were recorded at the SOLEIL synchrotron by high-resolution Fourier transform spectroscopy. Line centers are reported with a typical accuracy of 5 × 10−5 cm−1 for well isolated lines. The combined line list of about 9700 water lines was assigned to about 10 400 transitions of the nine stable water isotopologues (H2XO, HDXO, D2XO, with X = 16, 17, and 18). A total of 2885 transitions of eight bands involving the first five vibrational states were assigned to D216O. Among them, 2057 are newly reported. The obtained set of transition frequencies was merged with literature data to generate a new set of empirical energy levels for the first five vibrational states of D216O. A total of 1089 transitions of the (000)–(000) and (010)–(010) bands were measured for D217O. They were merged with literature sources to derive 724 empirical term values of seven vibrational states, up to 8088 cm−1. 348 D217O levels are newly determined. A set of 1150 transitions belonging to the (000)–(000) and (010)–(010) bands was measured for D218O. 3451 empirical energies of rotation–vibration levels up to 9222 cm−1 were retrieved using our observations and literature sources. The extension and accuracy of the derived empirical energy levels allow us to recommend new line lists with empirically corrected line positions for D216O, D217O, and D218O.

Гетерофазные явления при фракционировании трития в водных системах

Tritium is the only one of the radioactive isotopes that a filtering system is unable to neutralize. It is produced by collateral fission processes in nuclear reactors and displays itself in radioactive wastes and effluents in different forms of tritium oxides. Thus the development and application of nuclear energy entails a challenging problem of treating tritium-containing radioactive wastewater. The paper deals with tritium water isotopologues, namely, with prototritium water and deuterotritium water. Various approaches to the problem of tritium separation have been outlined. The choice of the appropriate process of water detritiation depends, first of all, on whether the detritiated water is recycled back to the reactor system or is discharged to the environment and on whether molecular tritium is to be extracted for further application. Special attention is paid to the process of electrosonochemical water detritiation which is shown to be the preferential one due to its ability to provide molecular tritium. Tritiated water decomposition should be preceded by its concentrating, the latter being two-stage and including water conditioning followed by providing concentrated tritiated water. Reverse-osmosis conditioning and salt rectification are considered as preferential techniques.

Comparison of phase diagrams of H2O, D2O, and inert substances

The phase diagrams for the light H2O, heavy D2O water, and inert substances (Ne, Ar, Kr, and Xe) have been compared. A method of choosing the starting point for entropy and internal energy was proposed. It allowed testing the principle of corresponding states using caloric variables. In the given coordinates of temperature, pressure, and chemical potential, the water isotopologues form one group of substances and have similar phase diagrams. The inert substances in the same coordinates form another group of substances with similar phase diagrams. The phase diagrams for inert Ne with significant de Boer quantum parameters differ to a certain extent from the phase diagrams of other inert substances.

Phase Formation in Solutions of Heavy Water Isotopologues

Phase Formation in Solutions of Heavy Water Isotopologues

Resolved ALMA observations of water in the inner astronomical units of the HL Tau disk

The water molecule is a key ingredient in the formation of planetary systems, with the water snowline being a favourable location for the growth of massive planetary cores. Here we present Atacama Large Millimeter/submillimeter Array data of the ringed protoplanetary disk orbiting the young star HL Tauri that show centrally peaked, bright emission arising from three distinct transitions of the main water isotopologue (H216O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathrm{H}}_{2}^{16}{\\mathrm{O}}$$\\end{document}). The spatially and spectrally resolved water content probes gas in a thermal range down to the water sublimation temperature. Our analysis implies a stringent lower limit of 3.7 Earth oceans of water vapour available within the inner 17 astronomical units of the system. We show that our observations are limited to probing the water content in the atmosphere of the disk, due to the high dust column density and absorption, and indicate that the main water isotopologue is the best tracer to spatially resolve water vapour in protoplanetary disks.

All paths lead to hubs in the spectroscopic networks of water isotopologues H216O and H218O

Network theory has fundamentally transformed our comprehension of complex systems, catalyzing significant advances across various domains of science and technology. In spectroscopic networks, hubs are the quantum states involved in the largest number of transitions. Here, utilizing network paths probed via precision metrology, absolute energies have been deduced, with at least 10-digit accuracy, for almost 200 hubs in the experimental spectroscopic networks of H216O and H218O. These hubs, lying on the ground vibrational states of both species and the bending fundamental of H216O, are involved in tens of thousands of observed transitions. Relying on the same hubs and other states, benchmark-quality line lists have been assembled, which supersede and improve, by three orders of magnitude, the accuracy of the massive amount of data reported in hundreds of papers dealing with Doppler-limited spectroscopy. Due to the omnipresence of water, these ultraprecise line lists could be applied to calibrate high-resolution spectra and serve ongoing and upcoming space missions.

Tree‐ and stand‐scale variability of xylem water stable isotope signatures in mature beech, oak and spruce

AbstractIn ecohydrology, water isotopologues are used to assess potential sources of root water uptake by comparing xylem water signatures with source water signatures. Such comparisons are affected by the variability and uncertainty of the isotope signatures of plant water and water sources. The tree‐scale and stand‐scale variabilities of the isotope signatures in stem xylem water are often unknown but are important for sampling design and uncertainty estimation in assessing the sources of tree water uptake. Here, we quantified tree‐scale and stand‐scale variabilities of xylem water isotope signatures in beech, oak and spruce trees in a mature forest on the Swiss plateau. For stem xylem water, sub‐daily replicates and replicates in different cardinal directions showed no systematic differences, but we found systematic differences with sampling height. The observed variability of isotope signatures at different heights along the stem suggests that water residence times within trees need to be considered, along with their effects on the isotope signatures in different compartments (stem, branches, leaves). Further, concerning the hydrogen signatures, we found height‐ and species‐specific offsets (SW‐excess δ2H). Stem xylem water's tree‐scale variability was similar in magnitude to its stand‐scale variability and smaller than the variabilities in branch xylem and bulk soil water around each tree. Xylem water from stem cores close to the ground, therefore, can give a more precise estimate of the isotopic signal of the most recent root water uptake and facilitate more accurate source water attribution.

Spectroscopic heat maps reveal how to design experiments to improve the uncertainties of transitions and energy levels present in line-by-line databases

Spectroscopic information systems contain enormous sets of line-by-line (LBL) data on characteristics of rovibronic transitions. Developers of these datasets are continuously improving transitions data, for example, via lowering the uncertainties of the transitions. Improved transition uncertainties may also result in a decrease in the uncertainties of the energies of some of the quantum states. This paper introduces a method that assesses the existing line lists and suggests wavenumber intervals for possible (re)measurements, based on their usefulness to improve the uncertainties of the transitions and/or the quantum-state energies. This is called the spectroscopic heat map method, which characterizes with two values all wavenumber intervals of a fixed length. The spectroscopic heat map method is tested on the example of seven water isotopologues and the most abundant isotopologue of acetylene, based on data present in the HITRAN information system.

Water vapor absorption spectroscopy and validation tests of databases in the far-infrared (50–720 cm−1). Part 2: H217O and HD17O

The present work is the second part of our systematic study of the absorption spectrum of the water vapor isotopologues by high resolution (≈ 0.001 cm−1) Fourier transform spectroscopy in the far infrared (50–721 cm−1). The room temperature spectra were recorded at the AILES beam line of the SOLEIL synchrotron with an absorption pathlength of 151.75 m. Here, we consider three spectra of a water vapor sample highly enriched in 17O. Line parameters retrieved from the three spectra were combined in a global list of 4432 water lines (assigned to 4651 transitions). The spectral calibration based on a statistical matching with about 370 accurate reference line positions of H216O allows for line center determinations with an accuracy of 5×10−5 cm−1 for well isolated lines of intermediate intensity. Six water isotopologues (H218O, H216O, H217O, HD18O, HD16O, and HD17O) were found to contribute to the spectrum. 460 and 99 of the measured H217O and HD17O transitions are newly observed by absorption spectroscopy. 69 H217O and 20 HD17O energy values of the ground (000) and first excited (010) states are newly determined.The present set of measured H217O line positions is combined with 24 literature sources to provide a list of 821 empirical energies for the first five vibrational states – (000), (010), (020), (100), and (001) – using the RITZ principle. A set of 332 rotational energies of the (000) and (010) states of HD17O is determined by merging the 465 HD17O transitions measured in the present study to eight literature sources.

High-Performance and Stability Electrochromic Devices with a Water Isotopologue.

In this report, an ammonium metatungstate (AMT) and ferrous chloride [Fe(II)Cl2] electrochromic liquid (ECL) was synthesized using a hydrothermal method, with D2O used as the solvent instead of H2O. The results show that the use of D2O can improve the stability and performance of ECLs. The hydrogen evolution process in electrochromic devices (ECDs) filled with ECL becomes more difficult, while the material exchange process becomes easier. The ECD exhibits a color modulation amplitude of 58%@680 nm at 2 V. After 500 cycles, the device's performance remains above 95% at a current density of 1.5 mA/cm2. Hydrogen bonds in D2O solutions are expected to exhibit stronger forces compared to those in regular H2O solutions. Therefore, we hypothesize that enhancing the strength of hydrogen bonds in H2O solutions is an effective approach for improving the performance and stability of electrochromic solutions.

The rotational excitation of the water isotopologues by molecular hydrogen

ABSTRACT We present cross-sections and rate coefficients for rotational transitions in the water isotopologues D2O, H$_2^{18}$O, and HDO induced by collisions with para-H2(j2 = 0) and ortho-H2(j2 = 1). Quantum scattering calculations are performed at the full close-coupling level with the isotopic variants of an accurate full-dimensional H2O−H2 interaction potential. The D2O, H$_2^{18}$O, and HDO cross-sections are compared to the corresponding cross-sections for H2O. Large isotopic effects are observed in the case of D2O and HDO, in particular for collisions with p-H2(j2 = 0), while the 18O isotopic substitution is found to be negligible. Rate coefficients are provided for rotational transitions among all para-D2O, ortho-D2O, and HDO levels with internal energy below 300 cm−1 and for kinetic temperatures in the range 5–300 K. Non-LTE radiative transfer calculations show that the HDO 225.9 GHz and H$_2^{18}$O 203.4 GHz transitions recently detected with ALMA in the young proto-planetary disc V883 Ori should be inverted (weak masers) in a large fraction of the disc.

Stratigraphic noise and its potential drivers across the plateau of Dronning Maud Land, East Antarctica

Abstract. Stable water isotopologues of snow, firn and ice cores provide valuable information on past climate variations. Yet single profiles are generally not suitable for robust climate reconstructions. Stratigraphic noise, introduced by the irregular deposition, wind-driven erosion and redistribution of snow, impacts the utility of high-resolution isotope records, especially in low-accumulation areas. However, it is currently unknown how stratigraphic noise differs across the East Antarctic Plateau and how it is affected by local environmental conditions. Here, we assess the amount and structure of stratigraphic noise at seven sites along a 120 km transect on the plateau of Dronning Maud Land, East Antarctica. Replicated oxygen isotope records of 1 m length were used to estimate signal-to-noise ratios as a measure of stratigraphic noise at sites characterised by different accumulation rates (43–64 mm w.e. a−1), snow surface roughnesses and slope inclinations. While we found a high level of stratigraphic noise at all sites, there was also considerable variation between sites. At sastrugi-dominated sites, greater stratigraphic noise coincided with stronger surface roughnesses, steeper slopes and lower accumulation rates, probably related to increased wind speeds. These results provide a first step to modelling stratigraphic noise and might guide site selection and sampling strategies for future expeditions to improve high-resolution climate reconstructions from low-accumulation regions.

Simple Self-Powered Sensor for the Detection of D2O and Other Isotopologues of Liquid Water.

Distinguishing between heavy water and regular water has been a continuing challenge since these isotopologues of water have very similar physical and chemical properties. We report the development and evaluation of a simple, inexpensive sensor capable of detecting liquid D2O and other isotopologues of liquid water through the measurement of electrical signals generated from a nanoporous alumina film. This electrical output, consisting of a sharp voltage pulse followed by a separate broad voltage pulse, is present during the application of microliter volumes of liquid. The amplitude and temporal characteristics of these pulses have been combined to enable four diagnostic parameters for sensing D2O and H218O. The sensing mechanism is based on different modification effects on the alumina surface by H2O and D2O, spatially localized variations in the surface potential of alumina induced by isotopically substituted water molecules, combined with the effect of isotopic composition on charge transfer. As a proof-of-concept demonstration, a sensing system has been developed that provides real-time detection of liquid D2O in a stand-alone system.

Isotope effects in dynamics of water isotopologues induced by core ionization at an x-ray free-electron laser.

Dynamical response of water exposed to x-rays is of utmost importance in a wealth of science areas. We exposed isolated water isotopologues to short x-ray pulses from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we identify significant structural dynamics with characteristic isotope effects in H2O2+, D2O2+, and HDO2+, such as asymmetric bond elongation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. A method to disentangle the sequences of events taking place upon the consecutive absorption of two x-ray photons is described. The obtained deep look into structural properties and dynamics of dissociating water isotopologues provides essential insights into the underlying mechanisms.

Off axis integrated cavity output spectroscopy of deuterated water isotopologues in 7178–7196 cm−1 spectral region

Water is one of the most abundant molecules on the earth and its isotopic composition measurements find application in various fields. Even though it is an extensively studied molecule, many absorption lines of its isotopologues are still unknown. In the recent years, a significantly improved sensitivity of spectroscopic methods has brought forth a scope of studying the weak and extremely challenging molecular transitions. The paper describes an off axis integrated cavity output spectroscopic investigation the deuterated water isotopologues, viz. HD16O, HD17O and HD18O, in the 7178–7196 cm−1 spectral region. A few new ro-vibrational transitions of HD18O are reported along with their line strengths and assignments. Apart from this, observation of extremely weak transitions of deuterated water isotopologues and comparison with existing database and published data is also presented. The present study will find application in field of accurate and sensitive HD16O, HD17O and HD18O detections.

Conformations and non-covalent interactions of cyclohexyl isothiocyanate and its water complex

The conformational equilibria of cyclohexyl isothiocyanate and its complex with water were studied by microwave spectroscopy combined with theoretical calculations. For the bare cyclohexyl isothiocyanate, the rotational spectra of the two conformers, namely a-trans and e-trans, were measured and analyzed. Additional mono-substituted isotopologues of two 13C and one 34S of a-trans and e-trans were also measured, which result in an accurate structural determination of the two conformers. For the binary complex with water, the rotational spectra were measured for the monohydrates of both a-trans and e-trans conformers. Water isotopologues were also detected for the monohydrates. All the measured rotational spectra show 14N quadrupole coupling hyperfine structures. Water molecule prefers linking to the isothiocyanate group through a OwH⋯S hydrogen bond and forming two CH⋯Ow hydrogen bonds with the oxygen atom of water acting as a proton acceptor. The non-covalent bonding features of the monohydrates were revealed by natural bond orbital analysis and symmetry-adapted perturbation theory analysis.

Hydrogen Exchange through Hydrogen Bonding between Methanol and Water in the Adsorbed State on Cu(111)

The interaction between submonolayers of methanol and water on Cu(111) is studied at 95-160 K temperature range with surface-sensitive infrared spectroscopy using isotopically labeled molecules. The initial interaction of methanol with the preadsorbed amorphous solid water at 95 K is through hydrogen-bonding with the dangling hydroxyl groups of water. Upon increasing the temperature up to 140 K, methanol and deuterated water form H-bonded structures which allow hydrogen-deuterium exchange between the hydroxyl group of methanol and the deuterated water. The evolution of the O-D and O-H stretching bands indicate that the hydrogen transfer is dominant at around 120-130 K, slightly below the desorption temperature of methanol. Above 140 K, methanol desorbs and a mixture of hydrogen-related water isotopologues remains on the surface. The isotopic composition of this mixture versus the initial D2O:CH3OH ratio supports a potential exchange mechanism via hydrogen hopping between alternating methanol and water molecules in a hydrogen-bonded network.