(Solid + solute) phase equilibria in aqueous solution. XIII. Thermodynamic properties of hydrozincite and predominance diagrams for (Zn2 + + H2O + CO2)

The thermodynamic properties ofZn₅(OH)₆(CO₃)₂ , hydrozincite, have been determined by performing solubility and d.s.c. measurements. The solubility constant in aqueous NaClO₄media has been measured at temperatures ranging from 288.15 K to 338.15 K at constant ionic strength (I =  1.00 mol · kg ^− 1). Additionally, the dependence of the solubility constant on the ionic strength has been investigated up to I =  3.00 mol · kg ^− 1NaClO₄at T =  298.15 K. The standard molar heat capacity C_{p, m}^ofunction fromT =  318.15 K to T =  418.15 K, as well as the heat of decomposition of hydrozincite, have been obtained from d.s.c. measurements. All experimental results have been simultaneously evaluated by means of the optimization routine of ChemSage yielding an internally consistent set of thermodynamic data (T =  298.15 K): solubility constant log ^* K_{ps 0}⁰ =  (9.0  ±  0.1), standard molar Gibbs energy of formationΔ_fG_m^o {Zn₅(OH)₆(CO₃)₂ }  =  ( − 3164.6  ±  3.0)kJ · mol ^− 1, standard molar enthalpy of formation Δ_fH_m^o{Zn₅(OH)₆(CO₃)₂ }  =  ( − 3584  ±  15)kJ · mol ^− 1, standard molar entropy S_m^o{Zn₅(OH)₆(CO₃)₂ }  =  (436  ±  50)J · mol ^− 1· K ^− 1and C_p,m^o / (J · mol ^− 1· K ^− 1)  =  (119  ±  11)  +  (0.834  ±  0.033)T / K. A three-dimensional predominance diagram is introduced which allows a comprehensive thermodynamic interpretation of phase relations in(Zn^2 +  +  H₂O  +  CO₂) . The axes of this phase diagram correspond to the potential quantities: temperature, partial pressure of carbon dioxide and pH of the aqueous solution. Moreover, it is shown how the stoichiometric composition{n(CO₃) / n(Zn)} of the solid compoundsZnCO₃ and Zn₅(OH)₆(CO₃)₂can be checked by thermodynamically analysing the measured solubility data.     

Equilibrium solubility of sodium 2-naphthalenesulfonate in binary (sodium chloride + water), (sodium sulfate + water), and (ethanol + water) solvent mixtures at temperatures from (278.15 to 323.15) K

The equilibrium solubility of sodium 2-naphthalenesulfonate in binary (sodium chloride + water), (sodium sulfate + water), and (ethanol + water) solvent mixtures was measured at elevated temperatures from (278.15 to 323.15) K using a steady-state method. With increasing temperatures, the solubility increases in aqueous solvent mixtures. The results of these results were regressed by a modified Apelblat equation. The dissolution entropy and enthalpy determined using the method of the least-squares and the change of Gibbs free energy calculated with the values of Δ_diffS^o and Δ_diffH^o at T = 278.15 K.     

Calorimetric investigation of mixing enthalpy of liquid (Co + Cu + Zr) alloys at T = 1873 K

The enthalpies of mixing of liquid (Co + Cu + Zr) alloys have been determined using the high-temperature isoperibolic calorimeter. The measurements have been performed along three sections (x_Co/x_Cu = 3/1, 1/1, 1/3) with x_Zr = 0 to 0.55 at T = 1873 K. Over the investigated composition range, the partial mixing enthalpies of zirconium are negative. The limiting partial enthalpies of mixing of undercooled liquid zirconium in liquid (Co + Cu) alloys are (−138 ± 18) kJ · mol⁻¹ (the section x_Co/x_Cu = 3/1), (−155 ± 10) kJ · mol⁻¹ (the section x_Co/x_Cu = 1/1), and (−130 ± 22) kJ · mol⁻¹ (the section x_Co/x_Cu = 1/3). The integral mixing enthalpies are sign-changing. The isenthalpic curves have been plotted on the Gibbs triangle. The main features of the composition dependence of the integral mixing enthalpy of liquid ternary alloys are defined by the pair (Co + Zr) and (Cu + Zr) interactions.     

Dissociation behaviour of (tetra-n-butylammonium bromide + tetra-n-butylammonium chloride) mixed semiclathrate hydrate systems

The thermal properties of {tetra-n-butylammonium bromide + tetra-n-butylammonium chloride (TBAB + TBAC)} mixed semiclathrate hydrates prepared from aqueous solutions were investigated by dissociation temperature measurements and differential scanning calorimetry (DSC). The maximum dissociation temperature of the mixed hydrate crystals at 0.1 MPa is 288.5 K for x_TBAB = 0.2 {mole fraction of TBAB to (TBAB + TBAC)}, which is higher than that of the pure hydrates {T = (285.5 and 288.2) K for TBAB and TBAC hydrates, respectively}. In addition, the dissociation enthalpies of the mixed hydrates are higher than those of the pure hydrates {(5.55 ± 0.06) kJ ⋅ mol⁻¹ H₂O for pure TBAB hydrate and (5.30 ± 0.05) kJ ⋅ mol⁻¹ H₂O for pure TBAC hydrate}, with a maximum of (5.95 ± 0.12) kJ ⋅ mol⁻¹ H₂O recorded at approximately x_TBAB = 0.4. It was therefore suggested that the crystal distortion in (TBAB + TBAC) mixed hydrates, caused by replacing water molecules by both bromide and chloride anions, was smaller than that observed for each pure hydrate. Consequently, the hydration numbers in the mixed hydrates were hypothesized to be slightly higher than those of the pure hydrates.     

The thermodynamic properties of DyBr3(s) and DyI3(s) from T=5 K to their melting temperatures

Low-temperature calorimetric measurements have been performed on DyBr₃(s) in the temperature range (5.5 to 420 K ) and on DyI₃(s) from T=4 K to T=420 K. The data reveal enhanced heat capacities below T=10 K, consisting of a magnetic and an electronic contribution. From the experimental data on DyBr₃(s) a C⁰_p,m (298.15 K) of (102.2±0.2) J·K⁻¹·mol⁻¹ and a value for {S⁰_m (298.15 K) − S⁰_m (5.5 K)} of (205.5±0.5) J·K⁻¹·mol⁻¹, have been obtained. For DyI₃(s), {S⁰_m (298.15 K) − S⁰_m (4 K)} and C⁰_p,m (298.15 K) have been determined as (226.9±0.5) J·K⁻¹·mol⁻¹ and (103.4±0.2) J·K⁻¹·mol⁻¹, respectively. The values for {S⁰_m (5.5 K) − S⁰_m (0)} for DyBr₃(s) and {S⁰_m (4 K) − S⁰_m (0)} for DyI₃(s) have been calculated, giving S⁰_m (298.15 K)=(212.3±0.9) J·K⁻¹·mol⁻¹ in case of DyBr₃(s) and S⁰_m (298.15 K) =(233.1±0.7) J·K⁻¹·mol⁻¹ for DyI₃(s). The high-temperature enthalpy increment has been measured for DyBr₃(s) in the temperature range (525 to 799 K) and for DyI₃(s) in the temperature range (525 to 627 K). From the results obtained and enthalpies of formation from the literature, thermodynamic functions for DyBr₃(s) and DyI₃(s) have been calculated from T→0 to their melting temperatures at 1151.0 K and 1251.5 K, respectively.     

A calorimetric and thermodynamic investigation of A2[(UO2)2(MoO4)O2] compounds with A = K and Rb and calculated phase relations in the system (K2MoO4 + UO3 + H2O)

A calorimetric and thermodynamic investigation of two alkali-metal uranyl molybdates with general composition A₂[(UO₂)₂(MoO₄)O₂], where A = K and Rb, was performed. Both phases were synthesized by solid-state sintering of a mixture of potassium or rubidium nitrate, molybdenum (VI) oxide and gamma-uranium (VI) oxide at high temperatures. The synthetic products were characterised by X-ray powder diffraction and X-ray fluorescence methods. The enthalpy of formation of K₂[(UO₂)₂(MoO₄)O₂] was determined using HF-solution calorimetry giving Δ_fH° (T = 298 K, K₂[(UO₂)₂(MoO₄)O₂], cr) = −(4018 ± 8) kJ · mol⁻¹. The low-temperature heat capacity, С_р°, was measured using adiabatic calorimetry from T = (7 to 335) K for K₂[(UO₂)₂(MoO₄)O₂] and from T = (7 to 326) K for Rb₂[(UO₂)₂(MoO₄)O₂]. Using these С_р° values, the third law entropy at T = 298.15 K, S°, is calculated as (374 ± 1) J · K⁻¹ · mol⁻¹ for K₂[(UO₂)₂(MoO₄)O₂] and (390 ± 1) J · K⁻¹ · mol⁻¹ for Rb₂[(UO₂)₂(MoO₄)O₂]. These new experimental results, together with literature data, are used to calculate the Gibbs energy of formation, Δ_fG°, for both phases giving: Δ_fG° (T = 298 K, K₂[(UO₂)₂(MoO₄)O₂], cr) = (−3747 ± 8) kJ · mol⁻¹ and Δ_fG° (T = 298 K, Rb₂[(UO₂)₂(MoO₄)], cr) = −3736 ± 5 kJ · mol⁻¹. Smoothed С_р°(Т) values between 0 K and 320 K are presented, along with values for S° and the functions [H°(T) − H°(0)] and [G°(T) − H°(0)], for both phases. The stability behaviour of various solid phases and solution complexes in the (K₂MoO₄ + UO₃ + H₂O) system with and without CO₂ at T = 298 K was investigated by thermodynamic model calculations using the Gibbs energy minimisation approach.     

Speeds of sound in {(1 − x)CH4 + xN2} with x = (0.10001, 0.19999, and 0.5422) at temperatures between 170 K and 400 K and pressures up to 30 MPa

The speed of sound in {(1 − x)CH₄ + xN₂} has been measured with a spherical acoustic resonator. Two mixtures with x = (0.10001 and 0.19999) were studied along isotherms at temperatures between 220 K and 400 K with pressures up to 20 MPa; a few additional measurements at p = (25 and 30) MPa are also reported. A third mixture with x = 0.5422 was studied along pseudo-isochores at amount-of-substance densities between 0.2 mol · dm⁻³ and 5 mol · dm⁻³. Corrections for molecular vibrational relaxation are discussed in detail and relaxation times are reported. The overall uncertainty of the measured speeds of sound is estimated to be not worse than ±0.02%, except for those measurements in the mixture with x = 0.5422 that lie along the pseduo-isochore at the highest amount-of-substance density. The results have been compared with the predictions of several equations of state used for natural gas systems.     

Thermodynamic properties of soddyite from solubility and calorimetry measurements

The release of uranium from geologic nuclear waste repositories under oxidizing conditions can only be modeled if the thermodynamic properties of the secondary uranyl minerals that form in the repository setting are known. Toward this end, we synthesized soddyite ((UO₂)₂(SiO₄)(H₂O)₂), and performed solubility measurements from both undersaturation and supersaturation. The solubility measurements rigorously constrain the value of the solubility product of synthetic soddyite, and consequently its standard-state Gibbs free energy of formation. The log solubility product (lg K_sp) with its error (1σ) is (6.43 + 0.20/−0.37), and the standard-state Gibbs free energy of formation is (−3652.2 ± 4.2 (2σ)) kJ mol⁻¹. High-temperature drop solution calorimetry was conducted, yielding a calculated standard-state enthalpy of formation of soddyite of (−4045.4 ± 4.9 (2σ)) kJ · mol⁻¹. The standard-state Gibbs free energy and enthalpy of formation yield a calculated standard-state entropy of formation of soddyite of (−1318.7 ± 21.7 (2σ)) J · mol⁻¹ · K⁻¹. The measurements and associated thermodynamic calculations not only describe the T = 298 K stability and solubility of soddyite, but they also can be used in predictions of repository performance through extrapolation of these properties to repository temperatures.     

The role of the double bond position in hydroboration using HBBr2 · SMe2, HBCl2 · SMe2 and H2BBr · SMe2: A detailed kinetic and mechanistic study

Hydroboration reactions of 4-octene with HBBr₂ · SMe₂, HBCl₂ · SMe₂ and H₂BBr · SMe₂ in CH₂Cl₂ were studied as function of concentration and temperature and compared with those of 1-octene. On average, hydroboration with dihaloborane proceeded 16 times slower for 4-octene than for 1-octene. In the case of the reactions with the monohaloborane, this factor is halved. This can be explained by the difference in the relative rates of dissociates of Me₂S from the dihaloborane and a monohaloborane complex, respectively. The reactions involving H₂BBr · SMe₂ also exhibited a k_?2 value, an indication of the presence of a parallel reaction, most likely a rearrangement process facilitating isomerization by way of a π-complex. The moderate ΔH^≠ values accompanied by small ΔS^≠ values (94 ± 4 kJ mol^?1, ?3 ± 13 J K^?1 mol^?1 for HBBr₂ · SMe₂; 93 ± 1 kJ mol^?1, ?17 ± 4 J K^?1 mol^?1 for HBCl₂ · SMe₂ and in the case of H₂BBr · SMe₂, 90 ± 13 kJ mol^?1, +12 ± 44 J K^?1 mol^?1 and 83 ± 13 kJ mol^?1, ?24 ± 45 J K^?1 mol^?1, respectively, for the k₂ and k_?2 processes) imply a process that is dissociatively dominated, with the overall mode of activation being interchange dissociative (I_d).     

On oxoacidic properties and solubilities of beryllium and magnesium oxides in molten (CsCs + KCl + NaCl) eutectic at T = 783 K

Reactions of Be²⁺ and Mg²⁺ with O^2– in molten eutectic mixture (CsCs + KCl + NaCl) (0.455:0.245:0.30) at T = 783 K were studied by a potentiometric method using Pt(O₂)|ZrO₂(Y₂O₃) indicator electrode. Addition of O^2– ions to the melt containing Mg²⁺ results in precipitation of MgO (pK_s,MgO = 11.89 ± 0.3, molality) whereas interaction of Be²⁺ with O^2– is accompanied with sequential formation of Be₂O²⁺ (pK = 15.68 ± 0.5, molality) and precipitation of BeO (pK_s,BeO = 9.62 ± 0.3, molality). On the basis of the obtained and known data pK_s,MgO–T⁻¹ dependence in molten (CsCs + KCl + NaCl) eutectic is constructed. The slope of the said dependence in T/K = (from 583 to 1073) range is in good agreement with the value predicted by the Shreder equation, that extends the range of use of the Shreder equation for predictions of metal oxide solubilities in molten halides.     

Study of bromide salts solubility in the (m1NaBr + m2MgBr2)(aq) system at T = 323.15 K. Thermodynamic model of solution behavior and (solid + liquid) equilibria in the (Na + K + Mg + Br + H2O) system to high concentration and temperature

The bromide minerals solubility in the mixed system (m₁NaBr + m₂MgBr₂)(aq) have been investigated at T = 323.15 K by the physico-chemical analysis method. The equilibrium crystallization of NaBr·2H₂O(cr), NaBr(cr), and MgBr₂·6H₂O(cr) has been established. The solubility-measurements results obtained have been combined with all other experimental equilibrium solubility data available in literature at T = (273.15 and 298.15) K to construct a chemical model that calculates (solid + liquid) equilibria in the mixed system (m₁NaBr + m₂MgBr₂)(aq). The solubility modeling approach based on fundamental Pitzer specific interaction equations is employed. The model gives a very good agreement with bromide salts equilibrium solubility data. Temperature extrapolation of the mixed system model provides reasonable mineral solubility at high temperature (up to 100 °C). This model expands the previously published temperature variable sodium–potassium–bromide and potassium–magnesium–bromide models by evaluating sodium–magnesium mixing parameters. The resulting model for quaternary system (Na + K + Mg + Br + H₂O) is validated by comparing solubility predictions with those given in literature, and not used in the parameterization process. Limitations of the mixed solution models due to data insufficiencies at high temperature are discussed.     

Thermodynamic evaluation and optimization of the (NaCl + KCl + AlCl3) system

All available phase equilibrium and thermodynamic data for the (NaCl + KCl + AlCl₃) system were collected and critically evaluated. An optimization was performed to obtain the parameters of one set of model equations for each phase (solids, liquid, gas) in order to best reproduce all the data simultaneously. In this way the data are rendered self-consistent, discrepancies among the data are identified, and extrapolations and interpolations can be performed. For the molten phase the Modified Quasichemical Model for short-range ordering was used, with monomeric Al³⁺ ions (corresponding to AlCl₄⁻ complexes in earlier models) predominating in alkali-rich melts, and dimeric aluminum species (corresponding to Al₂Cl₇⁻ complexes in previous models) predominating in AlCl₃-rich melts. No ternary model parameters were required for the liquid phase; the binary parameters suffice. The models can be used with Gibbs free energy minimization software to calculate phase diagram sections, vapor pressures, and all thermodynamic properties at all compositions and over extended ranges of temperature and pressure.     

Solubility of europium oxides in NaI melts at 700°C

The solubility product of EuO (pP _EuO = 8.65 ± 0.5) and its dissociation constant (pK _EuO = 5.67 ± 0.5) in NaI melts at 700°C have been determined by potentiometric titration with the use of a Pt(O₂)|ZrO₂(Y₂O₃) membrane oxygen electrode. Estimated on the basis of these parameters, the total solubility of EuO in NaI melts (1.12 × 10⁻³ mol/kg, logs _EuO = −2.95) is close to the value obtained by the consecutive additions method (2.8 × 10⁻³ mol/kg, logs _EuO = −2.55). The values obtained show that Eu²⁺ (EuI₂) is a stable cationic activator in NaI melt, but it yet cannot be recommended as an agent for the removal of oxygen-containing admixtures from this melt.     

Temperature dependence of the surface tension and 0.1 MPa density for 1-Cn-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate with n = 2, 4, and 6

Experimental air–liquid interfacial tension data and density data are presented for three 1-C_n-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphates (FAP), [C_nMIM][(C₂F₅)₃PF₃], with n = 2, 4, and 6, measured at atmospheric pressure in the temperature range from 267 K to 360 K using the Krűss K100MK2 tensiometer. The accuracy of the surface tension measurements was checked by employing the Wilhelmy plate and the du Noüy ring methods in parallel. The combined standard uncertainty associated with the Wilhelmy plate method is estimated to be ±0.1 mN · m⁻¹. The density data were obtained using buoyancy method with an estimated standard uncertainty less then ±0.4 kg · m⁻³ (3 · 10⁻⁴ϱ). The chloride anions decrease the density of the tris(pentafluoroethyl)trifluorophosphates of interest up to six times more effectively than they decrease the density of the imidazolium based tetrafluoroborates. A QSPR analysis of the surface tension of imidazolium based ionic liquids with BF₄, TFA, DCA, FAP, NTf₂, and PF₆ anions indicates, that the FAP ionic liquids fit well into the analyzed group of imidazolium based ionic liquids while those having hexafluorophosphate anion show anomalously high deviations of the experimental surface tension from the values predicted by the QSPR model.     

Thermochemistry of the biochemical reaction: { pyrophosphate(aq) + H2O(l) = 2 phosphate(aq)}

Calorimetric enthalpies of reaction have been measured for the overall biochemical reaction{pyrophosphate(aq)  +  H₂O(l)  =  2phosphate (aq)} . The reaction was catalyzed by alkaline phosphatase and, to simplify the thermochemistry, was carried out in the absence of Mg ^2 + (aq). Measurements were performed with phosphate buffer ( pH  =  7.19 and 7.94), PIPES buffer ( pH  =  7.13), and HEPES buffer ( pH  =  7.86). The results of these measurements were analyzed by using an equilibrium model. These calculations lead to the standard molar enthalpy changeΔ_rH_m^o =  − (17.3  ±  0.6)kJ·mol ^− 1 (temperature T =  298.15 K and ionic strengthI =  0) for the reference reaction{HP₂O₇^3 − (aq)  +  H₂O(l)  =  2HPO₄^2 − (aq)  +  H ⁺ (aq)} . Values of the apparent equilibrium constantK^′ for the overall biochemical reaction from the literature were also analyzed by using the equilibrium model in order to obtain what is believed to be a reliable value for the equilibrium constantK =  4.7 · 10 ^− 4 for the reference reaction. The values ofK and Δ_rH_m^o for the reference reaction have been used together with values from the CODATA tables to calculate standard molar formation properties for the pyrophosphate species.     

Theoretical enthalpies of formation of ROX (R=H, CH3; X=F, Cl, Br) compounds

Standard enthalpies of formation of ROX (R=H, CH₃; X=F, Cl, Br) compounds were theoretically estimated using hydrogenation reactions as working chemical reactions. Energy differences were computed at four ab initio levels of calculation, using gaussian-2 (G2) theory (Level I), coupled-cluster theory with split-valence basis set (Level II), coupled-cluster theory with triple-zeta basis set (Level III), and Truhlar's basis-set limit method (Level IV). The recommended standard enthalpies of formation (at 298.15 K and 1.0 atm) are the unweighted averages of the results obtained at Levels I and IV from the different hydrogenation reactions, namely: FOH, −21.1±0.3; ClOH, −18.5±0.5; BrOH, −15.2±1.1; CH₃OF, −19.1±2.1; CH₃OCl, −13.2±2.3, and CH₃OBr, −8.7±2.7 kcal mol⁻¹.     

A time-resolved study of the multiphase chemistry of excited carbonyls: Imidazole-2-carboxaldehyde and halides

Imidazole-2-carboxaldehyde (IC) reactivity in the presence of halide anions (Cl^–, Br^–, I^–) has been studied by laser flash photolysis in aqueous solution at room temperature. The absorption spectrum of the triplet state of IC has been measured with a maximum absorption at 330 nm and a weaker absorption band around 650 nm. Iodide anions proved to be efficient quenchers of the triplet state IC, with a rate coefficient k_q of (5.33 ± 0.25) × 10⁹ M⁻¹ s⁻¹. Quenching by bromide and chloride anions was less efficient, with k_q values of (6.27 ± 0.53) × 10⁶ M⁻¹ s⁻¹ and (1.31 ± 0.16) × 10⁵ M⁻¹ s⁻¹, respectively. The halide (X^–) quenches the triplet state; the resulting transient absorption feature matches that of the corresponding radical anion (X₂^–). We suggest that this type of quenching reactions is a driving force of oxidation reactions in the oceanic surface microlayer (SML) and a source of halogen atoms in the atmosphere.     

Crystal structures and magnetic properties of complexes of M(NO3)2; M = MnII,CoII, NiII,and CuII,with pyridine ligands carrying an aminoxyl radical

Four complexes of M(NO₃)₂(4NOPy-OMe)₂, (4NOPy-OMe = 4-(N-tert-butyloxylamino)-2-(methoxymethylenyl)pyridine, and M = Mn^II, 1; Co^II, 2; Ni^II, 3; Cu^II, 4), were prepared and fully characterized. X-ray single crystal analysis reveals that four complexes are isostructural. The molecular structures are distorted octahedral in which the methoxy oxygen atoms coordinate to the metal ion by trans-configuration while the pyridyl nitrogen atoms and the nitrate oxygen atoms coordinate by cis-configuration. The magnetic properties of all complexes were investigated by SQUID magneto/susceptometry. Temperature dependence of the molar magnetic susceptibilities in the temperature range of 2–300 K indicated that the magnetic coupling between aminoxyl radicals and metal ion was antiferromagnetic in the complex 1 and were ferromagnetic in the complexes 2–4. The quantitative analysis based on the spin Hamiltonian, H = −2J(S₁S_M + S_MS₂) yielded the best fit as J/k_B = −13.4 ± 0.1 K, g = 1.94 ± 0.002, and θ = −0.78 ± 0.02 K for the complex 1, J/k_B = 48.7 ± 2.1 K, g = 2.07 ± 0.02, and θ = −2.83 ± 0.41 K for the complex 3 (the data in the temperature range 300–50 K were used), and J/k_B = 57.0 ± 1.2 K, g = 2.002 ± 0.004, and θ = −9.8 ± 0.1 K for the complex 4.     

Isopiestic study of (calcium chloride + water) and (calcium chloride + magnesium chloride + water) atT = 313.15 K

The osmotic coefficients of aqueous calcium chloride solutions were experimentally determined atT =  313.15 K by the isopiestic method. Magnesium chloride served as the isopiestic standard for the calculation of osmotic coefficients. The molality range covered in this study correspond to about 0.1mol · kg ^− 1to 3.0mol · kg ^− 1. In addition, the osmotic coefficients of aqueous mixtures of calcium chloride and magnesium chloride were determined over the range of ionic strength levels of about 0.1mol · kg ^− 1to 9mol · kg ^− 1and at various mole fractions. The results obtained were correlated by the Pitzer equation.     

Hot band spectroscopy of CCO in the C–O stretching region: The (ν1 + 2ν3) − 2ν3 and (2ν1 + ν3) − (ν1 + ν3) bands

Two C–O stretching hot bands, (ν₁ + 2ν₃) − 2ν₃ and (2ν₁ + ν₃) − (ν₁ + ν₃), of the CCO radical in the ground electronic state were measured. These hot bands are red shifted by approximately 70 cm⁻¹ compared to the C–O stretching fundamental. CCO was produced in a discharge through a flowing mixture of carbon suboxide and helium. The spectra were recorded using a diode laser spectrometer. The band origins were determined to be 1904.32512(62) and 1902.69130(56) cm⁻¹ for (ν₁ + 2ν₃) − 2ν₃ and (2ν₁ + ν₃) − (ν₁ + ν₃), respectively. The measurements in this band together with previously reported frequencies in the C–C and C–O stretching regions were analysed to determine harmonic frequencies and anharmonicity constants.