18O 16O Research Articles

Rapid and accurate SIMS microanalysis of monazite oxygen isotopes

28Si–18O–16O simultaneous measurement by SIMS enables matrix-effect correction of monazite oxygen isotopes.

Selective catalytic reduction of NO by NH3 with WO3-TiO2 catalysts: Influence of catalyst synthesis method

A series of supported WO3/TiO2 catalysts was prepared by a new synthesis procedure involving co-precipitation of an aqueous TiO(OH)2 and (NH4)10W12O41*5H2O slurry under controlled pH conditions. The morphological properties, surface WOx molecular structures, surface acidity and surface chemistry of the co-precipitated WO3/TiO2 catalysts were determined with BET, in situ Raman, in situ IR, steady-state NO/NH3/O2 SCR and NO/NH3-temperature-programmed surface reaction (TPSR) spectroscopy, respectively. Time-resolved isotopic 18O–16O exchange with IR spectroscopy demonstrated that tungsten oxide was present as surface WOx sites on the TiO2 support with mono-oxo O=WO4 coordination. In contrast to previous studies employing impregnation synthesis that found only surface one mono-oxo O=WO4 site (1010–1016cm−1) on TiO2, the co-precipitation procedure resulted in the formation of two distinct surface WOx sites: mono-oxo O=WO4 (∼1012–1014cm−1) and a second mono-oxo O=WO4 (∼983–985cm−1). The new surface mono-oxo O=WO4 (∼983–985cm−1) site is thought to be associated with surface defects on the co-precipitated titania support. The co-precipitated catalysts exhibited slightly enhanced SCR reactivity that is thought to be related to the presence of the new surface O=WO4 sites. Additional factors, however, may also be contributing. This is the first study that attempts to relate the molecular level structural properties of co-precipitated WO3-TiO2 catalysts with their surface reactivity for SCR.

Oxygen-18 isotope of breath CO₂ linking to erythrocytes carbonic anhydrase activity: a biomarker for pre-diabetes and type 2 diabetes.

Carbonic anhydrase (CA), a well-characterized metalloenzyme, is associated with oxygen-18 ( 18O)-isotopic fractionations of CO2. To investigate how CA activity links the 18O of breath CO2 to pre-diabetes (PD) and type 2 diabetes (T2D) during metabolism, we studied pre- and post-dose CA activities in erythrocytes with simultaneous monitoring of 18O/ 16O-isotope ratios of breath CO2 and thereafter elucidated potential metabolic pathways underlying CA alteration in the pathogenesis of T2D. Here we show that the post-dose CA activity in both T2D and PD was markedly enhanced, whereas the non-diabetic controls (NDC) exhibited a considerable reduction in post-dose CA activity when compared with their basal CA activities. However, T2D and PD exhibited isotopic enrichments of 18O in breath CO2, while a marked depletion of 18O in CO2 was manifested in NDC. Thus, the isotopic enrichments and depletions of 18O in breath CO2 were well correlated with the changes in CA activities for controls, PD and T2D. Our findings suggest the changes in CA activities in erythrocytes may contribute to the pathogenesis of T2D and the breath C 18O 16O regulated by the CA activity as a potential biomarker for non-invasive assessment of T2D, and thus may open a new method for treating T2D.

Surface ReOx Sites on Al2O3 and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

Supported ReOx/Al2O3 catalysts were investigated for propylene metathesis as a function of surface rhenia loading and extensively characterized with in situ UV–vis, Raman, IR, XANES/EXAFS, and isotopic 18O–16O exchange studies. The experimental studies were complemented with DFT calculations using realistic models of the alumina surface. The surface ReOx sites were found to be isolated surface dioxo (O═)2ReO2 species, which represent the most stable surface rhenia structures on alumina as shown by DFT. Two distinct surface ReO4 species, however, were found to be present and only slightly differ in their bridging Re–O–Al bond lengths brought about by anchoring at different sites of the Al2O3 support. The deformed surface ReO4–I species preferentially anchor at more basic μ1 AlIV and μ1 AlVI sites and are difficult to activate for propylene metathesis. The surface ReO4–II species are formed at more acidic μ2 AlVI and μ3 AlVI sites and are the catalytic active sites for propylene metathesis. The surface ReO4–II sites were readily activated by propylene while the deformed surface ReO4–I sites were almost not affected by propylene, with only a few sites being activated. The steady-state propylene metathesis reaction rates are much higher for the surface ReO4–II sites than the deformed surface ReO4–I sites. The formation of the less reactive deformed surface ReO4–I species could be blocked by occupation of the μ1 AlIV sites with sacrificial surface TaOx species that resulted in catalysts exclusively containing the more active surface ReO4–II sites on alumina. This is the first study to demonstrate that the surface ReO4–II sites are the precursors for the catalytic active sites for propylene metathesis by supported ReO4/Al2O3 catalysts and to molecularly design olefin metathesis catalysts that exclusively contain isolated surface ReO4–II sites.

Oxygen surface exchange kinetics on PrBaCo2O5+δ

The surface oxygen exchange kinetics on the double perovskite PrBaCo2O5 + δ has been studied using pulse 18O–16O isotope exchange measurements in the temperature range from 300 to 500 °C. The exchange rate, at oxygen partial pressure of 0.21 atm, shows an activation energy of 97 ± 3 kJ mol−1. A two-step exchange mechanism is applied to account for the observed distribution of 16O2, 16O18O, and 18O2 in the effluent pulses. The results indicate that the oxygen exchange kinetics on PrBaCo2O5 + δ is determined by the rates of homolytic oxygen dissociative adsorption on the PrBaCo2O5 + δ surface and incorporation of oxygen adatoms in the oxide lattice. A changeover of the rate-determining step occurs upon increasing pO2 from 0.1 to 0.95 atm.

Dissociation of CO and H 2O during water–gas shift reaction on carburized Mo/Al 2O 3 catalyst

The dissociation of CO and H 2O during the water–gas shift reaction (WGSR) on the 973 K-carburized 4.8 and 8.5 wt% Mo/Al 2O 3 catalysts at 423 K was studied by in situ mass and infrared spectroscopies. It was found that both CO and H 2O were dissociated on the basis of the formation of H 2, 13C 18O, 13C 18O 2 and 13C 18O 16O after the injection of H 2 18O into the 13C 16O stream. Regarding the 12C- and 16O-labeled atoms, 12C 16O 2, 12C 16O 18O and 12C 18O 2 were not formed, but H 2 16O, 12C 16O, 12C 18O and 13C 16O 2 were formed. The H 2 16O, 12C 16O and 13C 16O 2 were formed by the reaction of the dissociated 16O of 13C 16O with the surface carbon or the lattice carbon atom of the Mo oxycarbide. The infrared spectroscopy results for the injection of H 2O into the C 18O flow showed that C 18O had no effect on forming the formate group. The formate and carbonate which were probably formed during the CO 2 hydrogenation were observed when using the 973 K-carburized Mo/Al 2O 3 catalyst and alumina in a stream of CO. The WGSR on the Mo oxycarbide of the carburized Mo/Al 2O 3 catalyst followed the redox route together with the dissociation-association mechanism.

Oxygen surface exchange kinetics of erbia-stabilized bismuth oxide

The surface oxygen exchange kinetics of bismuth oxide stabilized with 25 mol% erbia (BE25) has been studied in the temperature and pO2 ranges 773–1,023 K and 0.1–0.95 atm, respectively, using pulse-response 18O–16O isotope exchange measurements. The results indicate that BE25 exhibits a comparatively high exchange rate, which is rate determined by the dissociative adsorption of oxygen. Defect chemical considerations and the observed $$ p{{\hbox{O}}_2}^{1/2} $$ dependence of the rate of dissociative oxygen adsorption suggest electron transfer to intermediate superoxide ions as the rate determining step in surface oxygen exchange on BE25.

Similarity and differences in the oxidative dehydrogenation of C 2–C 4 alkanes over nano-sized VO x species using N 2O and O 2

The effect of O 2 and N 2O on alkane reactivity and olefin selectivity in the oxidative dehydrogenation of ethane, propane, n-butane, and iso-butane over highly dispersed VO x species (0.79 V/nm 2) supported on MCM-41 has been systematically investigated. For all the reactions studied, olefin selectivity was significantly improved upon replacing O 2 with N 2O. This is due to suppressing CO x formation in the presence of N 2O. The most significant improving effect of N 2O was observed for iso-butane dehydrogenation: S(iso-butene) was ca. 67% at X(iso-butane) of 25%. Possible origins of the superior performance of N 2O were derived from transient experiments using 18O 2 traces. 18O 16O species were detected in 18O 2 and 18O 2–C 3H 8 transient experiments indicating reversible oxygen chemisorption. In the presence of alkanes, the isotopic heteroexchange of O 2 strongly increased. Based on the distribution of labeled oxygen in CO x and in O 2 as well as on the increased CO x formation in sequential O 2–C 3H 8 experiments, it is suggested that non-lattice oxygen species (possibly of a bi-atomic nature) originating from O 2 are non-selective ones and responsible for CO x formation. These species are not formed from N 2O.

Seasonal and diurnal variations of 13C 18O 16O in air: Initial observations from Pasadena, CA

The budget of atmospheric CO 2 is widely studied using records of temporal and spatial variations of concentrations, δ 13C and δ 18O values. However, the number and diversity of sources and sinks prevents these alone from fully constraining the budget. Molecules containing two rare isotopes can serve as additional tracers and potentially provide additional, independent, constraints. We present data documenting seasonal and diurnal variations of CO 2 having a mass of 47 u (mostly 13C 18O 16O) in air from Pasadena, CA. We report these data using the ‘mass 47 anomaly’ (Δ 47), which is defined as the deviation of R 47(=[47]/[44]) from that expected for a random distribution of isotopologues. Between February 2004 and December 2005, Δ 47 showed a seasonal pattern that differed significantly from that expected based on thermodynamic equilibrium. During the year 2004 Δ 47 was 0.76‰ in winter, increased to 0.87‰ in summer and gradually decreased through the autumn to 0.81‰ at the end of the year. Δ 47 then increased again through the winter and spring of 2005 to 0.97‰ in summer followed by a decrease to 0.88‰ at the end of 2005. The seasonal variations cannot be accounted for by variations in the relative contribution of local fossil fuel sources. Diurnal variations were the combined effect of both fuel combustion and respiration having Δ 47 values of 0.41‰ and ca. 0.77‰, respectively. The seasonal cycle may be interpreted as a competition between low Δ 47 values in respiration and higher Δ 47 values resulting from CO 2-water exchange in photosynthesis.

Investigation of the oxygen evolution reaction on Ti/IrO 2 electrodes using isotope labelling and on-line mass spectrometry

Oxygen evolution on Ti/IrO 2 anodes has been studied in 1M HClO 4 electrolyte using 18O labelling together with differential electrochemical mass spectrometry (DEMS) measurements. It has been shown that during successive cyclic voltammetric measurements in H 2 18O containing electrolyte the amount of 16O 2 ( m/ z = 32) decreases, with a concomitant increase of 18O 16O ( m/ z = 34) after each cycle before reaching a steady state after four cycles. The obtained higher 16O 2 concentration in the evolved oxygen during the first scans is because 16O from the IrO 2 film contribute in the oxygen evolution reaction. Analysis of the experimental data has shown that the amount of lattice oxygen, which is involved in the oxygen exchange reaction, is in the order of 1% of the total IrO 2 loading. This is an indication that only the outer surface of the oxide electrode participates in the oxygen evolution reaction. In a second series of experiments it has been demonstrated that oxygen evolution on Ir 16O 2 in H 2 18O containing electrolyte result in the formation of Ir 18O 2. Consequently, we can conclude that the IrO 2 layers participate in the oxygen evolution reaction in acid media at least to a several monolayer extend.

Calibration of the carbonate ‘clumped isotope’ paleothermometer for otoliths

Paleothermometry is an essential tool for understanding past changes in climate. The ‘carbonate clumped isotope thermometer’ is a temperature proxy related to ordering of 13C and 18O in the carbonate lattice (based on measurements of 13C 18O 16O in CO 2 produced by acid digestion of carbonate). This thermometer has been previously calibrated for inorganic calcite and aragonitic corals [Ghosh P., Adkins J., Affek H., Balta B., Guo W. F., Schauble E. A., Schrag D., and Eiler J. M. (2006) C-13–O-18 bonds in carbonate minerals: a new kind of paleothermometer. Geochim. Cosmochim. Acta 70 (6), 1439–1456]. Here we determine the relationship between growth temperatures of aragonitic fish otoliths and abundances of 13C 18O 16O produced by acid digestion of those otoliths. Our calibration is based on analyses of otoliths from six species from four genera of modern fish sampled from a latitudinal transect of the Atlantic Ocean between 54° S and 65° N, plus one species from the tropical western Pacific. The temperatures at which fish otoliths precipitated were estimated by the mean temperature in the waters in which they lived, averaged over their estimated lifetimes. Estimated growth temperatures of our samples vary between 2 and 25 °C. Our results show that the abundance of 13C 18O 16O in CO 2 produced by acid digestion of fish otolith aragonite is a function of growth temperature, following the relationship: Δ 47 = 0.0568 × 10 6 T 2 - 0.0045 , where Δ 47 is the enrichment, in per mil, of 13C 18O 16O in CO 2 relative to the amount expected for a stochastic (random) distribution of isotopes among all CO 2 isotopologues, and T is the temperature in Kelvin. This relationship closely approaches that previously documented for inorganic calcite and aragonitic coral (Ghosh et al., 2006).

Temperature dependent pressure induced linewidths of [formula omitted] and 18O 16O transitions in nitrogen, oxygen and air

The temperature dependent pressure induced broadening of several oxygen resonant transitions have been measured. For O 2 16 the isolated magnetic fine-structure transition J N ′ ′ ← J N = 1 1 ← 1 0 and the magnetic rotational transition 3 2 ← 1 2 are investigated in both nitrogen and oxygen. Additionally, pressure broadening of the magnetic rotational transition of 18O 16O 2 1 ← 0 1 is measured in air. This work improves precision and accuracy of the linewidth of the fine-structure transition and provides the first temperature dependent linewidth measurements at higher frequency.

Solid phase epitaxy of Na-ion irradiated α-quartz: Cathodoluminescence, kinetics and surface morphology

Even at low fluences doping of quartz by ion implantation results in amorphization. Here we report on the measurement of cathodoluminescence and surface structures during solid phase epitaxy in Na-implanted α-quartz annealed in 18O2 atmosphere. Complete epitaxy was achieved under appropriate conditions of ion fluence, annealing temperature and time. The crystalline structure of the samples was studied by Rutherford backscattering channelling spectroscopy and the 18O–16O exchange between the matrix and 18O2 annealing gas by elastic recoil detection analysis. In the cathodoluminescence spectra taken at room temperature, five bands were identified and assigned to various defect centres. Two of the bands in the violet region at 3.25 and 3.65eV strongly vary in intensity at 843–1173K annealing temperature and appear to be intimately correlated with the presence of Na-ions in the implanted region of the matrix. Finally, atomic force microscopy enabled, for the first time, the observation of the correlation of surface structures and epitaxy.

13C– 18O bonds in carbonate minerals: A new kind of paleothermometer

The abundance of the doubly substituted CO 2 isotopologue, 13C 18O 16O, in CO 2 produced by phosphoric acid digestion of synthetic, inorganic calcite and natural, biogenic aragonite is proportional to the concentration of 13C– 18O bonds in reactant carbonate, and the concentration of these bonds is a function of the temperature of carbonate growth. This proportionality can be described between 1 and 50 °C by the function: Δ 47 = 0.0592 · 10 6 · T −2 − 0.02, where Δ 47 is the enrichment, in per mil, of 13C 18O 16O in CO 2 relative to the amount expected for a stochastic (random) distribution of isotopes among all CO 2 isotopologues, and T is the temperature in Kelvin. This relationship can be used for a new kind of carbonate paleothermometry, where the temperature-dependent property of interest is the state of ordering of 13C and 18O in the carbonate lattice (i.e., bound together vs. separated into different CO 3 2− units), and not the bulk δ 18O or δ 13C values. Current analytical methods limit precision of this thermometer to ca. ± 2 °C, 1σ. A key feature of this thermometer is that it is thermodynamically based, like the traditional carbonate–water paleothermometer, and so is suitable for interpolation and even modest extrapolation, yet is rigorously independent of the δ 18O of water and δ 13C of DIC from which carbonate grew. Thus, this technique can be applied to parts of the geological record where the stable isotope compositions of waters are unknown. Moreover, simultaneous determinations of Δ 47 and δ 18O for carbonates will constrain the δ 18O of water from which they grew.

Feasibility of quantifying ecosystem–atmosphere C 18O 16O exchange using laser spectroscopy and the flux-gradient method

Stable isotopes of carbon dioxide (CO 2) can be used as natural tracers to better understand carbon cycle processes and exchange pathways between the biosphere and atmosphere. In this study, we used a tunable diode laser (TDL) technique for continuous fast measurement of the stable isotopomers C 18O 16O and C 16O 2 and their ratio, δ a. The TDL system was configured to measure mixing ratios of [C 16O 2] and [C 18O 16O] at wavenumber frequencies of 2308.225 and 2308.416 cm −1, respectively. Two-minute precision (1 standard deviation) was 0.0004, 0.09 μmol mol −1, and 0.26‰ for [C 18O 16O], [C 16O 2] and δ a, respectively. Comparison of TDL and mass spectrometry flask measurements showed relatively good agreement ( r 2 = 0.94) with a standard deviation of 0.55‰ for the residual values. Estimates of the isotope signature of ecosystem flux components over a soybean ( Glycine max) field were examined. These data represent one of the first continuous flux measurements of C 18O 16O. The isotope signature of net ecosystem CO 2 exchange at night ranged from −15 to −7‰ and during the daytime from −40 to −20‰. A simple estimate of canopy-scale photosynthetic discrimination showed significant diurnal variation and averaged 10.5‰ (±8.8‰). The large difference between the isotope signature of respiration and midday canopy photosynthesis represented significant isotopic disequilibrium. Coupled with recent advances in measuring water vapor isotopomers with the TDL technique, a new opportunity is emerging to better understand the dynamics, complex interactions, and discrimination mechanisms controlling land-atmosphere C 18O 16O exchange.

Abundance of mass 47 CO 2 in urban air, car exhaust, and human breath

Atmospheric carbon dioxide is widely studied using records of CO 2 mixing ratio, δ 13C and δ 18O. However, the number and variability of sources and sinks prevents these alone from uniquely defining the budget. Carbon dioxide having a mass of 47 u (principally 13C 18O 16O) provides an additional constraint. In particular, the mass 47 anomaly (Δ 47) can distinguish between CO 2 produced by high temperature combustion processes vs. low temperature respiratory processes. Δ 47 is defined as the abundance of mass 47 isotopologues in excess of that expected for a random distribution of isotopes, where random distribution means that the abundance of an isotopologue is the product of abundances of the isotopes it is composed of and is calculated based on the measured 13C and 18O values. In this study, we estimate the δ 13C (vs. VPDB), δ 18O (vs. VSMOW), δ47, and Δ 47 values of CO 2 from car exhaust and from human breath, by constructing ‘Keeling plots’ using samples that are mixtures of ambient air and CO 2 from these sources. δ47 is defined as ( R 47 / R std 47 - 1 ) × 1000 , where R std 47 is the R 47 value for a hypothetical CO 2 whose δ 13C VPDB = 0, δ 18O VSMOW = 0, and Δ 47 = 0. Ambient air in Pasadena, CA, where this study was conducted, varied in [CO 2] from 383 to 404 μmol mol −1, in δ 13C and δ 18O from −9.2 to −10.2‰ and from 40.6 to 41.9‰, respectively, in δ47 from 32.5 to 33.9‰, and in Δ 47 from 0.73 to 0.96‰. Air sampled at varying distances from a car exhaust pipe was enriched in a combustion source having a composition, as determined by a ‘Keeling plot’ intercept, of −24.4 ± 0.2‰ for δ 13C (similar to the δ 13C of local gasoline), δ 18O of 29.9 ± 0.4‰, δ47 of 6.6 ± 0.6‰, and Δ 47 of 0.41 ± 0.03‰. Both δ 18O and Δ 47 values of the car exhaust end-member are consistent with that expected for thermodynamic equilibrium at∼200 °C between CO 2 and water generated by combustion of gasoline–air mixtures. Samples of CO 2 from human breath were found to have δ 13C and δ 18O values broadly similar to those of car exhaust–air mixtures, −22.3 ± 0.2 and 34.3 ± 0.3‰, respectively, and δ47 of 13.4 ± 0.4‰. Δ 47 in human breath was 0.76 ± 0.03‰, similar to that of ambient Pasadena air and higher than that of the car exhaust signature.

Structural characterization of the [formula omitted] compound of cytochrome c oxidase

The structural properties of a key transient oxygen intermediate of cytochrome c oxidase, P R, remain an enigma, although inferences have been drawn from its equilibrium analogues, P CO / O 2 , P H and P M. With resonance Raman spectroscopy, an oxygen isotope-sensitive band at 806 cm −1 was observed in P CO / O 2 produced by adding CO and O 2 to the resting enzyme. The vibrational band shifted to 771 cm −1 upon isotopic substitution of 16O 2 with 18O 2. The same modes at 806 and 771 cm −1 were present simultaneously when the mixed isotope, 18O 16O, was employed, indicating that in P CO / O 2 the O–O bond is cleaved, resulting in a Fe 4+ O 2− structure. This result unifies the nature of the three equilibrium analogues of the P R intermediate.

Pressure broadening measurement of submillimeter-wave lines of O 3

The pressure broadening coefficients and their temperature dependences for two submillimeter-wave transitions of ozone, one being monitored with Odin and the other to be monitored with JEM/SMILES and EOS-MLS, have been determined by using a BWO based submillimeter-wave spectrometer. The measurements have also been extended to one of the symmetric isotopic species, 16O 18O 16O. The isotopic species is observed in natural abundance and as a consequence the temperature dependence is not determined due to weak signal intensity. The pressure broadening parameters are determined with better than 1% accuracy, while the temperature dependence exponents are obtained within 1.5–3% accuracy for the normal species transitions.

High-resolution infrared spectra of 18O 16O 18O ozone isotopomer in the range 900–5000 cm −1: line positions

Continuing the systematic study of ozone high-resolution infrared spectra, we present in this paper the measurements and analyses of line positions for the 18O 16O 18O isotopomer. In the range 900–5000 cm −1, corresponding to the observed spectra, 15 bands are analysed: ν 1, ν 3, ν 2+ ν 3, ν 1+ ν 2, 2 ν 3, ν 1+ ν 3, 2 ν 1, ν 2+2 ν 3, ν 1+ ν 2+ ν 3, 3 ν 3, 2 ν 1+ ν 3, ν 2+3 ν 3, ν 1+3 ν 3, ν 1+ ν 2+3 ν 3, and 5 ν 3. As in the case of 16O 3, 18O 3, and 16O 18O 16O, the analysis of these bands is performed using effective rovibrational Hamiltonians for nine polyads of interacting upper vibrational states. To correctly reproduce all observed transitions, we have to account for resonance perturbations due to 13 “Dark” states: (0 3 0), (0 4 0), (2 1 0), (0 3 1), (1 0 2), (0 4 1), (1 1 2), (3 1 0), (0 3 2), (0 0 4), (3 2 0), (0 1 4), and (0 4 2). We present the range of observed transitions, the results for spectroscopic parameters (vibrational energy levels, rotational and centrifugal distortion constants, and resonance coupling parameters), as well as the statistics for rovibrational energy levels, calculations and measurements. A comparison of observed band centres with those predicted from an isotopically invariant potential function is discussed. The RMS deviation between predicted and directly observed band centres is ≈0.03 cm −1 up to 3000 and ≈0.25 cm −1 for all 16 bands up to 5000 cm −1.

High-Resolution Infrared Spectra of the 16O 18O 16O Ozone Isotopomer in the Range 900–5000 cm −1: Line Positions

In pursuing the systematic study of ozone high-resolution infrared spectra, we present here the analysis of line positions of the 16O 18O 16O isotopomer. The recorded spectra cover the range 900–5000 cm −1, that has allowed 13 bands to be observed: ν 1, ν 3, 2ν 2, ν 2+ν 3, ν 1+ν 2, ν 1+ν 3, ν 1+ν 2+ν 3, 3ν 3, 2ν 1+ν 3, ν 2+3ν 3, ν 1+3ν 3, ν 1+ν 2+3ν 3, and 5ν 3. The analysis of these bands has been performed using effective rovibrational Hamiltonians for 10 polyads of interacting upper vibrational states. To correctly reproduce all observed transitions, it has been necessary to account for resonance perturbations due to “dark” states: (002), (200), (012), (210), (102), (310), (004), (014), (320), (104), and (311). We present the results for spectroscopic parameters (vibrational energy levels, rotational and centrifugal distortion constants, and resonance coupling parameters), as well as the statistics for rovibrational energy levels, range of observed transitions, and typical example of wavefunction mixing coefficients. A comparison of observed band centers with those predicted from an isotopically invariant potential function is discussed. The R.M.S. deviation between predicted and directly observed band centers is ≈0.2 cm −1 up to 2800 cm −1 and ≈0.5 cm −1 for all 13 bands up to 4800 cm −1.