H2 17O Research Articles

The absorption spectrum of the H2 14O radioactive isotopologue of water vapour

ABSTRACT The predicted rotation-vibration absorption spectrum of the radioactive isotopically substituted water molecule, H2 14O, is presented. Variational nuclear-motion calculations are performed using the DVR3D software package based on the use of a high-precision potential energy function and an accurate dipole moment surface. Line centres, intensity and Einstein coefficients are calculated, and air pressure broadening coefficients are estimated. The calculation was carried out over a wide wavenumber range from 0 to 25000 cm − 1 and total angular momentum up to J = 20. Isotopologue extrapolation rules based on experimental data on the energy levels of the stable isotopologues H2 16O, H 2 16 O H2 17O and H2 18O were also used to improve the predicted line positions. Spectral ranges best suited to the detection of H2 14O are identified.

Cavity ring down spectroscopy of water vapour near 750 nm: a test of the HITRAN2020 and W2020 line lists

Cavity ring down spectroscopy (CRDS) is used to measure with unprecedented sensitivity and accuracy the weak water vapour spectrum in the 13,171–13,417 cm−1 region. A total of more than 1400 water lines are rovibrationally assigned to four isotopologues in natural isotopic abundance (H2 16O, H2 18O, H2 17O and HD16O), leading to the determination of 151 new levels and correction of 160 levels. The review of previous experimental works in the region is discussed. The comparison to the recent HITRAN2020 spectroscopic databases and to the W2020 line lists [Furtenbacher et al. J. Phys. Chem. Ref. Data 49 (2020) 043103; doi:10.1063/5.0030680] shows important discrepancies both for line positions and line intensities. A significant fraction of the W2020 line positions is inaccurate and shows deviations compared to measurements largely exceeding their claimed error bars. Line intensities are poorly predicted by available ab initio calculations in the considered region. A recommended line list mostly based on the present CRDS measurements is proposed.

Rotranslational dynamics of confined water. II. Spectroscopic evidence of confinement effects on the far-infrared spectra of water isotopologues in argon and krypton matrices.

Water molecules trapped in rare gas matrices exhibit conspicuous shifts in their far-infrared (FIR), rotranslational spectral features compared with the corresponding transitions observed in the gas phase. These confinement-induced perturbations have been related not only to the quantization of translational motion but also to the coupling between the orientational and positional degrees of freedom: the rotation-translation coupling (RTC). As the propensity displayed by the nuclear spin isomers (NSI) of water to undergo interconversion in confinement is intimately related to how its nuclear spin degrees of freedom are coupled with those for intra- and intermolecular motions, confinement-induced RTC should also strongly impact the NSI interconversion mechanisms and rates. Insight into the rotranslational dynamics for H2 16O, H2 17O, and H2 18O, confined in argon and krypton matrices, is provided here based on the evolution of rotranslational spectra induced by NSI interconversion while a definitive assignment is provided from the transition energies and intensities calculated using the confined rotor model [Paper I, Wespiser et al., J. Chem. Phys. 156, 074304 (2021)]. In order to build a complete rotranslational energy diagram of confined water, which is fundamental to understand the NSI interconversion rates, the energy difference between the ground ortho and para rotranslational states is derived from the temperature dependence of the intensity ratio of mid-infrared lines emerging from these states. These investigations should provide deeper insight of the factors that control NSI interconversion of water isotopologues under extreme confinement.

Spectroscopic investigation of hydrogen and triple-oxygen isotopes in atmospheric water vapor and precipitation during Indian monsoon season

ABSTRACT Water vapor, the most important greenhouse gas in the atmosphere, has four natural stable isotopologues (H2 16O, H2 17O, H2 18O and HD16O), and their isotopic compositions can be used as hydrological tracers. But the underlying processes and pattern-dynamics of the isotopic compositions of atmospheric water vapor and precipitation in response to various meteorological conditions during monsoon season in a tropical hot and humid region is poorly understood. Here, we present results of H and triple-O-isotopes of water in precipitation and atmospheric water vapor during monsoon season exploiting high-resolution integrated cavity output spectroscopy technique. We observed a distinct temporal variation of the isotopic compositions of water at different phases of the monsoon. The diurnal patterns of the isotopic variations were influenced by the local meteorological factors such as temperature, relative humidity and amount of precipitation. We also investigated the monsoonal dynamics of the second-order isotopic parameters, so-called d-excess and 17O-excess along with the influence of local meteorological factors on isotopic variations to improve our understanding of the underlying isotopic fractionation processes. Consequently, our results provide a unique isotopic-fingerprint dataset of rainwater and atmospheric water vapor for a tropical region and thus shed a new light on hydrological and meteorological processes in the atmosphere.

Catching a comet. Rosetta begins its comet tale. Introduction.

Catching a comet. Rosetta begins its comet tale. Introduction.

Synthesis of N‐methylmorpholine N‐(17O‐oxide) and N‐methylmorpholine 15N‐(17O‐oxide)

AbstractN‐Methylmorpholine N‐(17O‐oxide) and N‐methylmorpholine 15N‐(17O‐oxide) were prepared from N‐methylmorpholine and 15N‐methylmorpholine by oxidation with H2 17O2. The facile one‐pot procedure provided yields of 82 and 76%, respectively. The labeled hydrogen peroxide was obtained by electrolysis of H2 17O followed by autoxidation of 2‐ethylanthraquinol with the molecular oxygen 17O2 generated. The compounds serve for mechanistic studies into gold nanoparticle generation in NMMO solution. Copyright © 2009 John Wiley & Sons, Ltd.

The assignment of quantum numbers in the theoretical spectra of the H2 16O, H2 17O, and H2 18O molecules calculated by variational methods in the region 0–26000 cm−1

Quantum numbers have been assigned in the theoretical spectra of three isotopologues of the water molecule: H2 16O, H2 17O, and H2 18O. The spectra were calculated by variational methods in the region 0–26000 cm−1 at a temperature of 296 K. For each molecule, the quantum numbers are assigned to more than 28000 levels. The quantum numbers are assigned to 216766, 210679, and 211073 spectral lines of the H2 16O, H2 17O, H2 18O molecules, respectively. The theoretical spectra with the assigned quantum numbers are available in the Internet.

Sugar Fragmentation in the Maillard Reaction Cascade: Formation of Short-Chain Carboxylic Acids by a New Oxidative α-Dicarbonyl Cleavage Pathway

The formation of short-chain carboxylic acids was studied in Maillard model systems (90 degrees C, pH 6-10) with emphasis on the role of oxygen and water. The total amount of acetic acid formed did not depend on the reaction atmosphere. In the presence of labeled dioxygen or water (18O2, H2 17O), labeled oxygen was partially incorporated into acetic acid. Thermal treatment of 1-deoxy-d-erythro-2,3-hexodiulose (1) and 3-deoxy-d-erythro-hexos-2-ulose in the presence of 17O-enriched water under alkaline conditions led to acetic and formic acid, respectively, as indicated by 17O NMR spectroscopy. The suggested mechanism involves an oxidative alpha-dicarbonyl cleavage leading to an intermediary mixed acid anhydride that releases the acids, e.g., acetic and erythronic acid, from 1. Similarly, glyceric and lactic acids were formed from 1-deoxy-3,4-hexodiuloses, corroborated by complementary analytical techniques. This paper provides for the first time evidence for the direct formation of acids from C6-alpha-dicarbonyls by an oxidative mechanism and incorporation of a 17OH group into the carboxylic moiety. The experimental data obtained support the coexistence of at least two newly described reaction mechanisms leading to carboxylic acids, i.e., (i) a hydrolytic beta-dicarbonyl cleavage as a major pathway and (ii) an alternative minor pathway via oxidative alpha-dicarbonyl cleavage induced by oxidizing species.

A new concept for sensitive in situ stable isotope ratio infrared spectroscopy based on sample modulation

Diode-laser absorption spectroscopy finds increasing applications in the emerging field of stable isotope research. To meet the requirements of the water isotopes measurement challenge in environmental research, ways have to be found to cope with the present limitations of spectroscopic systems. In this article, we discuss an approach based on the Stark effect in molecular spectra to reduce the influence of time-dependent, unwanted background structures generally superimposed on the desired signal from the spectral feature under investigation. A road map to high-sensitivity isotopic ratio measurements of water isotopes is presented. On the basis of an Allan Variance analysis of measured data, the detection limits have been calculated as a function of the integration time. To achieve the required optical density of about 6×10−7 for H2 17O measurements, the duty cycle has to be optimized and the implementation of a sample modulation within an optical multipass cell is a promising approach to increase the stability of spectroscopic instrumentation required for ecosystem research and airborne atmospheric platforms.

In vivo17O NMR approaches for brain study at high field

17O is the only stable oxygen isotope that can be detected by NMR. The quadrupolar moment of 17O spin (I = 5/2) can interact with local electric field gradients, resulting in extremely short T1 and T2 relaxation times which are in the range of several milliseconds. One unique NMR property of 17O spin is the independence of 17O relaxation times on the magnetic field strength, and this makes it possible to achieve a large sensitivity gain for in vivo 17O NMR applications at high fields. In vivo 17O NMR has two major applications for studying brain function and cerebral bioenergetics. The first application is to measure the cerebral blood flow (CBF) through monitoring the washout of inert H2 17O tracer in the brain tissue following an intravascular bolus injection of the 17O-labeled water. The second application, perhaps the most important one, is to determine the cerebral metabolic rate of oxygen utilization (CMRO2) through monitoring the dynamic changes of metabolically generated H2 17O from inhaled 17O-labeled oxygen gas in the brain tissue. One great merit of in vivo 17O NMR for the determination of CMRO2 is that only the metabolic H2 17O is detectable. This merit dramatically simplifies both CMRO2 measurement and quantification compared to other established methods. There are two major NMR approaches for monitoring H2 17O in vivo, namely direct approach by using 17O NMR detection (referred as direct in vivo 17O NMR approach) and indirect approach by using 1H NMR detection for measuring the changes in T2- or T1rho-weighted proton NMR signals caused by the 17O-1H scalar coupling and proton chemical exchange (referred as indirect in vivo 17O NMR approach). Both approaches are suitable for CBF measurements. However, recent studies indicated that the direct in vivo 17O NMR approach at high/ultrahigh fields appears to offer significant advantages for quantifying and imaging CMRO2. New developments have further demonstrated the feasibility for establishing a completely noninvasive in vivo 17O NMR approach for imaging CMRO2 in a rat brain during a brief 17O2 inhalation. This approach should be promising for studying the central role of oxidative metabolism in brain function and neurological diseases. Finally, the similar approach could potentially be applied to image CMRO2 noninvasively in human brain.

Vibrations of excited molecules at combination and difference frequencies

In the context of the theory of molecular vibrations, by applying the direct product operation of matrices, an equation for the vibrations of vibrationally excited molecules at combination and difference frequencies is obtained. From the solution of this equation, elements of vibration patterns and expressions that can be used for the study of changes in the molecular structural parameters and the coefficients of kinematic interactions are determined. The formulas obtained are applied to the calculation of the anharmonic electro-optical parameters of the molecules of water H2O and its two isotopes H2 17O and H2 18O. These calculations are performed in terms of the semiempirical quantum-chemical CNDO/2 method and by numerical differentiation of dipole moment functions by employing a cubic spline approximation.

Rotational spectra of the Kr-H2O van der Waals complex

Rotational spectra of the Kr-H2O van der Waals complex were measured in the frequency range 4–19 GHz using a pulsed jet cavity Fourier transform microwave spectrometer. The isotopomers studied include those of H2O, HDO, D2O, H2 17O and H2 18O with the six most abundant isotopes of Kr. A tunnelling splitting due to a large amplitude internal motion of the H2O subunit that exchanges bonded and non-bonded hydrogen atoms was observed. Nuclear quadrupole hyperfine structure was resolved and measured for the complexes containing 83Kr, D, and l7O, and the corresponding nuclear quadrupole coupling constants were determined. These were used to estimate structural parameters and to derive information about the intermolecular dynamics. The results, and in some instances the spectroscopic constants themselves, were compared with experimental and theoretical data previously reported for Ar-H2O.

Translational and rotational motion of isolated water molecules in nitromethane studied using O17 NMR

Hydrogen bonding plays an enormous role in determining the solution properties of liquid water. In the present study, the translational diffusion and the reorientational correlation times of isolated water (H2 17O) molecules dissolved in nitromethane were studied using O17 NMR measurements in the temperature range of 260–314 K. It was found that the water diffusion coefficient was considerably faster than in pure water at the same temperature. Further, the activation energy for the translational motion of the water was about 10 kJ mol−1, which was the same as that of the (solvent) nitromethane. However, the activation energy for the reorientational motion of the water was significantly less at 7.7 kJ mol−1. In this study we show that the motions of the isolated water molecules behave significantly different than water molecules in pure water due to the absence of hydrogen bonding to nearby water molecules.

Calculated nuclear shielding surfaces in the water molecule; prediction and analysis of σ(O), σ(H) and σ(D) in water isotopomers

Ab initio, internal valence coordinate oxygen and hydrogen nuclear shielding surfaces for the water molecule are presented. Calculations have been performed at the MCSCF level of theory using gauge-including atomic orbitals and a large basis set. The shielding at each of 37 points on the oxygen surface and 49 points on the hydrogen surface was calculated. The results were fitted to Taylor series expansions and are reported to second order in the coordinates. The correlated proton surface is little different from a coupled Hartree-Fock surface calculated some time ago but the oxygen surface is changed considerably by the inclusion of electron correlation. The surfaces have been averaged over the nuclear motion using a very recent, highly accurate force field to give values of σ(O), σ(H) and σ(D) for selected isotopomers over a range of temperature. For the oxygen shielding the dominant nuclear motion contribution comes from the first order stretching term which is deshielding as is normally the case. Important contributions are also made by the second order stretching term (also deshielding) and the second order bending term (which gives greater shielding). For low density H2 17O vapour at 300 K the calculated oxygen shielding of 333.723 ppm is in good agreement with an experimental value of 344 (±17) ppm. The 17O-isotope shifts of HD17O and D2 17O relative to H2 17O are calculated to be 1.356 ppm and 2.697 ppm which are in excellent agreement with recently observed liquid-phase values of 1.4203(1) ppm and 2.8324(1) ppm. The very slight non-additivity in these figures comes predominantly from the second order bending contribution. Expressions for the temperature dependence of the absolute oxygen and proton shielding in low density water vapour are proposed in the absence of experimentally determined ones. The calculated proton shielding at 300 K is 30.232 ppm which is in very good agreement with the experimental value of 30.052(15) ppm. The negative nuclear motion corrections to the proton shielding are almost entirely governed by the stretching of the OH bond containing the proton with the second order term partially cancelling the first order term. The proton isotope shift of HD16O with respect to H2 16O is calculated to be 0.039 ppm at 300 K; this is close to the value of 0.0304(1) ppm observed in solution. A recent experimental value for the temperature dependence of the H2 16O/H2 18O proton isotope shift occurring in the sixth significant figure of shielding is too small to be calculated with the present level of accuracy.

Calculated spin-spin coupling surfaces in the water molecule; prediction and analysis of J (O,H), J (O,D) and J (H,D) in water isotopomers

Ab initio symmetry and internal valence coordinate oxygen–proton and proton–proton spin–spin coupling surfaces for the water molecule have been computed for the first time. Calculations have been performed at the SOPPA (CCSD) level using a large basis set and a grid of forty-nine geometries on the two surfaces. Equilibrium values differ significantly from some other calculated values especially for the Fermi contact terms. The bond length dependence of J(O, H) is ‘normal’ i.e. J(O, H1) is much more sensitive to stretching the O–H1 bond than the O–H2 bond. This contrasts greatly with the corresponding situation in methane. The surfaces have been averaged over the nuclear motion using a recent highly accurate force field to give values of J (O, H) and J (O, D) for H2 17O, HD17O and D2 17O and J(H, D) for HD16O, HD17O and HD18O over a range of temperatures. For J (O, H) and J (O, D) bond stretching at first order is the dominant part of the nuclear motion correction with second order bending making an important contribution. For J (H, D) the second order bending is by far the largest contribution to the nuclear motion corrections although the other terms partially cancel this contribution. Non-additivity can be largely attributed to the bending term for J (O, H). As expected, the bending terms also contribute relatively more to the temperature dependence of the couplings for J (O, H), J (O, D) and J (H, D). Our calculated J (O, H) in H2 17O of -77.22Hz at 293K is in very good agreement with Wasylishen and Friedrich's observed value of -78.70 (±0.02) Hz in cyclohexane at this temperature. Our calculated J(H, D) in HD 16O at 323K of -1.233Hz is close to a recent experimental value of -1.114 (±0.003) Hz in nitromethane-d 3 observed by Sergeyev et al. at that temperature.

The use of molecular dynamics simulations withab initioSCF calculations for the determination of the oxygen-17 quadrupole coupling constant in liquid water

Molecular dynamics simulations for H2 17O were performed with two different potentials from the literature. After equilibration, snapshots were taken at intervals and the configurations thereby obtained used to randomly select clusters of molecules. For the central oxygen of these clusters the electric field gradient was then calculated with standard ab initio self-consistent field (SCF) calculations. The field gradients were converted to quadrupole couplings with a factor obtained previously in gas phase calculations and averaged to obtain the 17O coupling in liquid water. At 300 K a best estimate of 8·9 ± 0·3 MHz for the coupling constant and 0·72 ± 0·04 for η were found. The coupling constant at 360 K is about 0·1 MHz larger but the temperature dependence is not significant.

Determination of the rate of cerebral oxygen consumption and regional cerebral blood flow by non-invasive 17O in vivo NMR spectroscopy and magnetic resonance imaging. Part 2. Determination of CMRO2 for the rat by 17O NMR, and CMRO2, rCBF and the partition coefficient for the cat by 17O MRI.

The rate of oxygen consumption (CMRO2) in intact rat and cat brains was calculated by novel data analysis methods from data obtained in in vivo 17O NMR spectroscopy and imaging inhalation studies. Data analysis methods of 17O inhalation measurements are applied to the calculation of CMRO2, regional cerebral blood flow (rCBF), the reflow (R), the arterial venous difference (AVD) and the partition coefficient (lambda). Several of the applied methods for the determination of CMRO2 do not require measurements of regional cerebral blood flow and H2 17O arterial concentration. The proposed methods have been tested, and the results obtained by the different methods are in very good agreement. It is shown that 17O NMR is unique in providing the rate of blood water flow, where the natural abundance 17O NMR signal consists of an internal reference and that lambda is essentially 1. The average values of CMRO2 for rats and cats were found to be 2.09 +/- 0.35 and 1.18 +/- 0.58 (mumol/O2/g tissue)/min, respectively. The average value for rCBF for the cat was found to be 0.38 +/- 0.12 [(mg/g)/min]. The average value for lambda was found to be 1.00 +/- 0.04. The ratio of AVD due to organs other than the brain to AVD due to the brain is smaller than 1 for the rat and the cat. The time and spatial resolution accuracy of the spectroscopic and imaging methods are compared, discussed and statistically analysed. It is concluded that the accuracy of determination of CMRO2 for the rat is higher than for the cat by a factor of 8.

Calculation of nuclear spin–spin couplings. VII. Electron correlation effects on the five coupling mechanisms

Electron correlation effects on the five mechanisms in the indirect nuclear spin–spin coupling tensors are computed for H 19F, H2 17O,14NH3,13CH4, H 35Cl, 33SH2, 31PH3, and 29SiH4. The five coupling mechanisms consist of Fermi-contact (FC), spin-dipole (SD), Fermi-contact and spin-dipole cross term (FC/SD), orbital paramagnetic (OP), and orbital diamagnetic (OD) terms. Electron correlation contributions through the second order are calculated by the finite-field many-body perturbation theory (FF-MBPT). The results show an extremely large contribution of the (FC/SD) cross term to the anisotropic part of the couplings. The FC contribution is dominant in the isotropic part, but the OP term is considerable in HF, HCl, and H2O. Electron correlation effects are large in the FC contribution. They are small, but not negligible, in the other terms except in the OD term.

Proton spin–lattice relaxation rate in supercooled H2O and H2 17O under high pressure

The proton spin–lattice relaxation rate has been investigated as a function of pressure (p≤250 MPa), temperature (180 K≤T≤300 K), and oxygen-17 enrichment (25.7 atom-%, 50.7 atom-%) in metastable water. Intramolecular proton–oxygen 17 dipolar interactions in light water in relation to deuterium electric quadrupole interactions in heavy water carry similar dynamic information and allow the complicated dynamic isotope effect in liquid water to be investigated in the whole metastable range. Under hydrostatic pressure the proton relaxation rate curve R1 (T, p, ωH) has been investigated at five different Larmor frequencies (100 MHz≤ω≤500 MHz). These experiments unequivocally prove the isotropy of reorientational motions of water molecules on a nanosecond time scale and demonstrate the necessity to include fast quasilattice vibrations into a consistent interpretation of the relaxation rates in the dispersion regime.

Synthesis of oxygen‐17 labeled thyrotropin releasing hormone

AbstractOxygen‐17 isotope was introduced into the α‐carboxyl group of L‐proline and L‐pyroglutamic acid by acid catalysed exchange of oxygen‐17 from H2 17O or acid hydrolysis of respective amino acid methyl esters in presence of HCl/H2 17O. The α‐amino group of the amino acids were protected by tertbutyloxycarbonylation. Two analogues of thyrotrop in releasing hormone, one enriched with [17O] at the proline carboxamide oxygen (I) and the other at the pyroglutamic acid's amide oxygen (II) were synthesized using Merrifield method of solid phase peptide synthesis.