The state of metals in the Pt/Al2O3 and (Pt-Cu)/Al2O3 catalysts as indicated by IR spectroscopy with isotope dilution of 12C16O with 13C18O molecules

Adsorption of ¹³C¹⁸O+¹²C¹⁶O mixtures on the Pt(2.9%)/γ-Al₂O₃, (Pt(2.6%)+Cu(2.7%))/γ-Al₂O₃, and (Pt(2.6%)+Cu(5.1%))/γ-Al₂O₃ catalysts was studied by FTIR spectroscopy. On the metallic Pt surface at coverages close to saturation, CO is adsorbed both strongly and weakly to form linear species for which the vibrational frequencies of the isolated ¹³C¹⁸O molecules adsorbed on Pt are ∼1940 and ∼1970 cm⁻¹, respectively. The redistribution of intensities of the high-and low-frequency absorption bands in the spectra of adsorbed ¹³C¹⁸O indicates that these linear forms are present on the adjacent metal sites. The weak adsorption is responsible for the fast isotope exchange between the gaseous CO and CO molecules adsorbed on metal. The Pt-Cu alloys, in which the electronic state of the surface Pt atoms characteristic of monometallic Pt remains unchanged, are formed on the surface of the reduced Pt-Cu bimetallic catalysts. The decrease in the vibrational frequencies of the isolated C=O bonds in the isolated Pt-CO complexes suggests that the CO molecules adsorbed on the Cu atoms affect the electronic properties of Pt. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–836, May, 2007.     

Detection of vibration-rotational band 5-0 of 12C16O X 1sigma+ with cavity ringdown absorption near 0.96 microm

We have recorded extremely weak absorption in the overtone band 5-0 of 12C16O X 1sigma+ near 0.96 microm with cavity ringdown spectroscopy; the light source was a Raman-shifted dye laser pumped with a frequency-doubled Nd:YAG laser. This band shows lines in branch P to be much more intense than corresponding lines in branch R, in contrast to all lower overtone bands v-0 (v = 1-4). This reversal in relative intensity is explained quantitatively in terms of a radial function for the electric dipolar moment of CO. We have estimated absorption line strengths for P3-P18 in band 5-0 of 12C16O; these strengths are consistent with a pure vibrational matrix element <5/p(x)/0> = (3.6 +/- 0.3) x 10(-36) C m of the electric dipolar moment p(x), a Herman-Wallis coefficient C0(5) of about -0.1, and a band strength of (5.1 +/- 1.3) x 10(-29) m at 293 K.     

Pt电极上CO的同位素取代吸附机理研究

本文依据偶极耦合理论和相干势近似方法,合理选择粗糙电极上吸附分子的频率分布函数、一氧化碳(CO)吸附层的结构参数以及偶极耦合作用常数,对13CO/12CO同位素取代过程记录的红外光谱进行了拟合.研究发现,只有在拟合过程中引入低频CO分子优先取代,就可成功地模拟整个同位素取代过程的红外光谱随表面吸附的13CO/12CO组分的变化,并由此提出了吸附驱动的脱附机理,COad的脱附不是热激发脱附,而是吸附到表面的CO分子为其邻近位置COad的脱附提供能量.伸缩振动频率较低的COad处于台阶或缺陷位等较开阔的位置(尽管其吸附能较高),周围有较大的空间,利于来自溶液的CO分子的吸附,因此在台阶或缺陷位优先发生同位素的取代.     

Concentration-dependent frequency shifts and Raman spectroscopic noncoincidence effect of the C=O stretching mode in dipolar mixtures of acetone/dimethyl sulfoxide. Experimental, theoretical, and simulation results

The nu(C=O) Raman band frequencies of acetone have been analyzed to separate the contributions of the environmental effect and the vibrational coupling to the gas-to-liquid frequency shifts of this band and to elucidate the changes in these two contributions upon dilution in DMSO. We have measured the frequencies of the nu((12)C=O) band in acetone/DMSO binary mixtures, the nu((13)C=O) band of the acetone-(13)C=O present as a natural abundance isotopic impurity in these mixtures, and both the nu((12)C=O) and nu((13)C=O) bands in the acetone-(12)C=O/acetone-(13)C=O isotopic mixtures at infinite dilution. These frequencies are compared with those of the nu((12)C=O) band in the acetone/CCl(4) binary mixtures measured previously. We have found the following three points: (i) The negative environmental contribution for the nu((12)C=O) oscillator of acetone completely surrounded by DMSO is reduced in magnitude by +5.5 cm(-1) and +7.8 cm(-1) upon the complete substitution of DMSO with acetone and CCl(4) molecules, respectively, indicating the progressive reduction of the attractive forces exerted by the environment on the nu((12)C=O) mode of acetone. (ii) In DMSO and other solvents, the contribution of the vibrational coupling to the frequency of the isotropic Raman nu((12)C=O) band of acetone becomes progressively more negative with increasing acetone concentration up to a value of -5.5 cm(-1), while the contribution to the frequency of the anisotropic Raman band remains approximately unchanged. The only difference resides in the curvatures of the concentration dependencies of these contributions which depend on the relative solute/solvent polarity. (iii) The noncoincidence effect (separation between the anisotropic and isotropic Raman band frequencies) of the nu(C=O) mode in the acetone/DMSO mixtures exhibits a downward (concave) curvature, in contrast to that in the acetone/CCl(4) mixtures, which shows an upward (convex) curvature. This result is supported by MD simulations and by theoretical predictions and is interpreted as arising from the reduction and enhancement of the short-range orientational order of acetone in the acetone/DMSO and acetone/CCl(4) mixtures, respectively.     

An isotopic-independent highly accurate potential energy surface for CO2 isotopologues and an initial (12)C(16)O2 infrared line list

An isotopic-independent, highly accurate potential energy surface (PES) has been determined for CO(2) by refining a purely ab initio PES with selected, purely experimentally determined rovibrational energy levels. The purely ab initio PES is denoted Ames-0, while the refined PES is denoted Ames-1. Detailed tests are performed to demonstrate the spectroscopic accuracy of the Ames-1 PES. It is shown that Ames-1 yields σ(rms) (root-mean-squares error) = 0.0156 cm(-1) for 6873 J = 0-117 (12)C(16)O(2) experimental energy levels, even though less than 500 (12)C(16)O(2) energy levels were included in the refinement procedure. It is also demonstrated that, without any additional refinement, Ames-1 yields very good agreement for isotopologues. Specifically, for the (12)C(16)O(2) and (13)C(16)O(2) isotopologues, spectroscopic constants G(v) computed from Ames-1 are within ±0.01 and 0.02 cm(-1) of reliable experimentally derived values, while for the (16)O(12)C(18)O, (16)O(12)C(17)O, (16)O(13)C(18)O, (16)O(13)C(17)O, (12)C(18)O(2), (17)O(12)C(18)O, (12)C(17)O(2), (13)C(18)O(2), (13)C(17)O(2), (17)O(13)C(18)O, and (14)C(16)O(2) isotopologues, the differences are between ±0.10 and 0.15 cm(-1). To our knowledge, this is the first time a polyatomic PES has been refined using such high J values, and this has led to new challenges in the refinement procedure. An initial high quality, purely ab initio dipole moment surface (DMS) is constructed and used to generate a 296 K line list. For most bands, experimental IR intensities are well reproduced for (12)C(16)O(2) using Ames-1 and the DMS. For more than 80% of the bands, the experimental intensities are reproduced with σ(rms)(ΔI) < 20% or σ(rms)(ΔI∕δ(obs)) < 5. A few exceptions are analyzed and discussed. Directions for future improvements are discussed, though it is concluded that the current Ames-1 and the DMS should be useful in analyzing and assigning high-resolution laboratory or astronomical spectra.     

Branching ratio measurements of the predissociation of 12C16O by time-slice velocity-map ion imaging in the energy region from 108,000 to 110,500 cm(-1)

Direct branching ratio measurements of the three lowest dissociation channels of (12)C(16)O that produce C((3)P) + O((3)P), C((1)D) + O((3)P), and C((3)P) + O((1)D) are reported in the vacuum ultraviolet region from 108,000 cm(-1) (92.59 nm) to 110,500 cm(-1) (90.50 nm) using the time-slice velocity-map ion imaging and nonlinear resonant four-wave mixing techniques. Rotationally, resolved carbon ion yield spectra for both (1)Σ(+) and (1)Π bands of CO in this region have been obtained. Our measurements using this technique show that the branching ratio in this energy region, especially the relative percentages of the two spin-forbidden channels, is strongly dependent on the particular electronic and vibrational energy levels of CO that are excited.     

Helium clusters seeded with CO molecules: new results for HeN-13C18O and the approach to the nanodroplet limit

Infrared spectra of helium clusters seeded with doubly substituted carbon monoxide molecules, 13C18O, have been studied in order to complement recent helium nanocluster results and to determine whether additional isotopic data would help to separate vibrational and rotational contributions to the observed transitions. The experiments were made by direct infrared absorption in pulsed supersonic jet expansions using a tunable diode laser probe in the region of the fundamental band (approximately 2045 cm-1 for 13C18O). Even with data on the R0 transitions from four CO isotopomers, it was found that a clear and consistent separation of vibration and rotation could not be achieved for HeN-CO clusters in the size range N approximately 10-20. Isotope shifts observed for clusters with 13C18O (relative to 12C16O) were found to be close to the sums of the shifts previously determined for 13C16O and 12C18O. The new measurements generally supported previous assignments of cluster size, but some modifications for the range N=14-16 are suggested here. New measurements for HeN-12C16O under conditions favoring larger clusters (high backing pressure and low jet temperature) showed that individual transitions could be resolved even at N approximately 50. For larger clusters, a partly resolved "lump" of transitions was observed to approach the nanodroplet limit.     

Raman,infrared and force field studies of K2(12)C2O4 x H2O and K2(13)C2O4 x H2O in the solid state and in aqueous solution,and of (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O in the solid state

The Raman and infrared spectra of solid K2(12)C2O4 x H2O are reported together with, for the first time, the corresponding Raman and infrared spectra of solid K2(13)C2O4 x H2O. Raman spectra of aqueous solutions of both isotopomers are also reported. In the solid state the oxalate anion is planar with D2h symmetry in this salt, whereas in aqueous solution the Raman spectra of the anion are best interpreted on the basis of D2d symmetry. The Raman spectra of solid (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O, in which the oxalate anion is twisted from planarity by 28 degrees about the CC bond, have also been recorded. Several reassignments have been made. The harmonic force field for the oxalate anion in the D2h, D2 and D2d geometries has been determined in part, and approximate values of key valence force constants determined. All the observed band wavenumbers and 12C/13C isotopic shifts are well reproduced by the force fields. The potential energy distribution of the totally symmetric normal modes of planar oxalate indicates that each mode consists of extensively mixed symmetry corrdinates and that the labels previously used for the bands seen here at 475 and 879 cm(-1) would better be described as v(CC) and deltaS(CO2), respectively, putting them in the same wavenumber order as v(NN) and deltaS(NO2) for the isoelectronic and isostructural molecule N2O4. The stretching force constants of N2O4 and planar C2O4(2-) are established to be in the order f(NN) < f(CC) and f(NO) > f(CO), consistent with the known relative bond lengths.     

担载的NaRuCo_3(CO)_(12)络合物及其分散型Ru-Co双金属催化剂

担载于Al_2O_3上的NaRuCO_3(CO)_(12)络合物在IR光谱上出现类似于Ru(CO)_2O_2络合物特征带的羰基带,在300～400℃左右变强,在CO中尤为明显。在以ZrO_2为载体时出现与原来络合物相近的弱羰基带。当CO吸附于以Al_2O_3为载体的脱羰基催化剂上时,发现在氧化态催化剂上也出现了与担载络合物相似的吸收带,在还原态催化剂上只出现线式带。吸附于以ZrO_2为载体的脱羰基催化剂上的CO不出现CO的IR吸收带,在He中亦无TPD脱附物,在H_2中却可发生加氢反应生成CH_4。从Na~+和ZrO_2协同效应角度,探讨了CO在上述两种分散型催化剂上吸脱附行为不同的原因。     

Vibrational distributions of the CO(v) products of the C2H2 + O(3P) and HCCO + O(3P) reactions studied by FTIR emission

The C2H2 + O(3P) and HCCO + O(3P) reactions are investigated using Fourier transform infrared (FTIR) emission spectroscopy. The O(3P) radicals are produced by 193 nm photolysis of an SO2 precursor or microwave discharge in O2. The HCCO radical is either formed in the first step of the C2H2 + O(3P) reaction or by 193 nm photodissociation of ethyl ethynyl ether. Vibrationally excited CO and CO2 products are observed. The microwave discharge experiment [C2H2 + O(3P)] shows a bimodal distribution of the CO(v) product, which is due to the sequential C2H2 + O(3P) and HCCO + O(3P) reactions. The vibrational distribution of CO(v) from the HCCO + O(3P) reaction also shows its own bimodal shape. The vibrational distribution of CO(v) from C2H2 + O(3P) can be characterized by a Boltzmann plot with a vibrational temperature of approximately 2400 +/- 100 K, in agreement with previous results. The CO distribution from the HCCO + O(3P) reaction, when studied under conditions to minimize other processes, shows very little contamination from other reactions, and the distribution can be characterized by a linear combination of Boltzmann plots with two vibrational temperatures: 2320 +/- 40 and 10 300 +/- 600 K. From the experimental results and previous theoretical work, the bimodal CO(v) distribution for the HCCO + O(3P) reaction suggests a sequential dissociation process of the HC(O)CO++ --> CO + HCO; HCO --> H + CO.     

Vibrational frequencies of the homoleptic cobalt carbonyls: Co4(CO)12 and Co6(CO)16

The homoleptic cobalt carbonyls Co4(CO)12 and Co6(CO)16 are characterized by their equilibrium geometries, thermochemistry, and vibrational frequencies using density functional theory (DFT) methods with the B3LYP, BLYP, and BP86 functionals. The B3LYP predicted CoCo distances are 2.51 and 2.47 A for the C3v and Td structures, respectively, of Co4(CO)12. The global minimum for Co4(CO)12 has C3v symmetry with three bridging and nine terminal carbonyls. The 2.51 and 2.52 A CoCo distances suggest the single bond required for an 18-electron configuration for the metal atoms. This structure is close to an experimentally realized structure. A more symmetrical Co4(CO)12 structure with Td symmetry, analogous to that observed in the valence isoelectronic Ir4(CO)12 molecule, lies approximately 28 kcal/mol higher in energy and exhibits a small imaginary vibrational frequency ( approximately 40i). It has a slightly shorter CoCo distance of 2.47 A. Both Co4(CO)12 structures satisfy the 18-electron rule. The Co6(CO)16 structure has Td symmetry and satisfies the Wade-Mingos rules for an octahedral cluster. The nu(CO) carbonyl frequencies for both Co4(CO)12 and Co6(CO)16 computed with the BP86 functional are closer to the experimental values than those computed with the B3LYP and BLYP functionals. The structure of Co6(CO)16 is not known experimentally, but the BP86 functional predicts 2.56 A (CoCo), 1.77 and 2.02 A (CoC), and 1.66 and 1.20 A (CO) for the bond distances.     

Theoretical Study on Two C_(16)H_(12)O_4 Isomers of Derivatives of Pagodane

1 NTRODUCTION Pagodane ([1.1.1.1]-pagodane) is the trivial name assigned to the D2h-symmetry undecacyclic poly- quinane undecacyclo-[9.9.0.01,5.02,12.02,18.03,7.06,10. 08,12.011,15.013,17.316,20]-eicosane (Fig. 1). It has been synthesized[1] and subsequently studied by Prinzbach and co-workers for more than twenty years[2, 3]. Des- cribed as a waxy solid melting without decomposi-tion and stable to at least 600 ℃ in gas phase, pa- godane is interesting for its exotic structure and as an…     

FTIR spectroscopy combined with isotope labeling and quantum chemical calculations to investigate adsorbed bicarbonate formation following reaction of carbon dioxide with surface hydroxyl groups on Fe2O3 and Al2O3

FTIR spectroscopy combined with isotope labeling experiments and quantum chemical calculations is used to investigate the adsorption of carbon dioxide on hydroxylated metal oxide surfaces. In particular, transmission FTIR spectra following CO2 adsorption on hydroxylated nanoparticulate Fe2O3, alpha-Al2O3, and gamma-Al2O3 particles at 296 K are reported. As expected, reaction of CO2 with these surfaces results in the formation of adsorbed bicarbonate and carbonate. In this study, the vibrational spectrum of the bicarbonate product is analyzed in detail through the use of isotope labeling experiments and quantum chemical calculations. The experimental and calculated vibrational frequencies of adsorbed HC16O3-, DC16O3-, HC18O3-, HC16O18O2-, and HC18O16O2- indicate that bicarbonate bonds to the surface in a bridged structure. There is some evidence from the mixed isotope experiments that following initial nucleophilic attack of OH, the formation of the final bicarbonate structure involves a proton transfer. On the basis of energetic considerations, the proton transfer mechanism most likely occurs through an intermolecular process involving either coadsorbed hydroxyl groups and/or carbonate.     

Identification of the D(3h) isomer of carbon trioxide (CO3) and its implications for atmospheric chemistry.

The CO3 molecule is considered an important reaction intermediate in the atmospheres of Earth and Mars for quenching electronically excited oxygen atoms and in contributing to the anomalous 18O isotope enrichment. The geometry of the CO3 intermediate plays an important role in explaining these effects; however, only the cyclic (C(2v)) isomer has been experimentally confirmed so far. Here, we report on the first spectroscopic detection of the acyclic (D(3h)) isomer of carbon trioxide (12C16O3) via its nu1 and nu2 vibrational modes centered around 1165 cm(-1) under matrix isolation conditions; the identification of the 12C18O3, 13C16O3, 13C18O3, 16O12C18O2, and 18O12C16O2 isotopomers of the acyclic isomer confirms the assignments.     

Rh/Al2O3上CO和NO的吸附性能及相互作用

利用ＴＰ－ＩＲ动态方法研究了ＣＯ和ＮＯ在Ｒｈ／Ａｌ２Ｏ３上吸附性能和相互作用的动态行为，结果表明，Ｒｈ／Ａｌ２Ｏ３的孪生中心对ＣＯ的吸附强于对ＮＯ的吸会，线式和桥式中心则对ＮＯ的吸附强于对ＣＯ的吸附，ＣＯ和ＮＯ共吸附－ＴＰ（ＣＯ和ＮＯ中）－ＩＲ动态过程结果揭示出２２２４ｃｍ＾－１谱带的出现和强度的增加与孪生ＣＯ谱带以及吸附的ＮＯ谱带的强度减弱同时发生，表明是由吸附的ＮＯ和孪生ＣＯ形成Ｒｈ－ＮＣＯ。     

Sensitized fluorescence (A 1Π−X 1Σ+ and b 3Σ+−a 3Π) of 12C16O, 13C16O,and 12C18O by Kr(3P1) and Kr(1P1)

The Kr(³P₁) state was shown to excite preferentially the A ¹Π υ′ = 13 state of ¹³C¹⁶O and ¹²C¹⁸O by a resonance process. No resonance energy transfer was observed between Kr(³P₁) and ¹²C¹⁶O. The Kr(¹P₁) state was shown to excite the b ³Σ⁺ υ′ = O and υ′= 1 states of ¹²C¹⁶O, ¹³C¹³O by a non-resonance process.     

Doping of calcium in C(60) fullerene for enhancing CO(2) capture and N(2)O transformation: a theoretical study

Recently, capturing or transforming greenhouse gases, such as CO(2) and N(2)O, have attracted considerable interest from the perspective of environmental protection. In the present work, by studying CO(2) and N(2)O adsorption on pristine and calcium (Ca)-decorated fullerenes (C(60)) with density functional theory (DFT) methods, we have evaluated the potential application of this C(60)-based complex for the capture of CO(2) and transformation of N(2)O. The results indicate that the adsorptions of CO(2) and N(2)O molecules on the pristine C(60) are considerably weak accompanied by neglectable charge transfer. When C(60) is decorated with Ca atoms, however, it is found that CO(2) and N(2)O adsorptions on the C(60) are greatly enhanced. Up to five CO(2) molecules can be adsorbed on the CaC(60) system due to the electrostatic interaction. For N(2)O molecule, it is first molecularly adsorbed on the Ca atom with the adsorption energy of -0.534 eV, followed by the N(2) formation with a low barrier and high exothermicity. Moreover, when four Ca atoms are decorated on the surface of C(60), the maximum number of the adsorbed CO(2) molecules is 16. Our results might be useful not only to widen the potential applications of fullerene but also to provide an effective method to capture or transform greenhouse gases.     

Near-infrared spectroscopic study of [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 nitrate crystals formed by forced hydrolysis of Al3+ in the presence of TEOS

The polymer [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.0 in the presence of monomeric orthosilicic acid. Crystalline material was obtained by slow evaporation. Although the near-infrared spectra of the Al13-sulfate and Al13-O-Si(OH)3 are very similar, there are differences related to the bonding of the -O-Si(OH)3 group to the Al13-unit. The strong complex of bands around 7000 cm(-1) associated with the overtones and combination bands of the OH-stretching modes for Al13-sulfate is much weaker for Al13-O-Si(OH)3 and the opposite is true for the complex of bands around 5000 cm(-1) associated with the water overtone and combination modes, suggesting that the outer OH-groups of the Al13-unit are involved in the formation of the new Al13-O-Si(OH)3 units. A weak band around 7370-7631 cm(-1) is interpreted as the overtone of the Si-OH stretching vibration around 3740 cm(-1). A low intensity band, absent for Al13-sulfate and -nitrate is observed around 5550-5570 cm(-1) and is interpreted as the overtone of the OH-stretching mode of the OH-groups in the vicinity of the central AlO4 in the Al13-unit around 2890-2935 cm(-1). The interaction between the -O-Si(OH)3 group and the Al13-unit has a small influence on other bands like the combination modes of water in the 4400-4800 cm(-1) region, which show a small shift towards higher wavenumbers. The internal OH-groups in the Al13-complex are relatively shielded by the water molecules and therefore do not reflect the influence of the -O-Si(OH)3 in their band positions.     

Infrared spectra of H(2)16O, H(2)18O and D(2)O in the liquid phase by single-pass attenuated total internal reflection spectroscopy

Mid-infrared attenuated total internal reflection (ATR) spectra of H(2)16O, H(2)18O and D(2)16O in the liquid state were obtained and normal coordinate analysis was performed based on the potential energy surface obtained from density functional theory (DFT) calculations. Fits of the spectra to multiple Gaussians showed a consistent fit of three bands for the bending region and five bands for the stretching region for three isotopomers, H(2)16O, H(2)18O and D(2)16O. The results are consistent with previous work and build on earlier studies by the inclusion of three isotopomers and mixtures using the advantage of single-pass ATR to obtain high quality spectra of the water stretching bands. DFT calculation of the vibrational spectrum of liquid water was conducted on seven model systems, two systems with periodic boundary conditions (PBC) consisting of four and nine H(2)16O molecules, and five water clusters consisting of 4, 9, 19, 27 and 32 H(2)16O molecules. The PBC and cluster models were used to obtain a representation of bulk water for comparison with experiment. The nine-water PBC model was found to give a good fit to the experimental line shapes. A difference is observed in the broadening of the water bending and stretching vibrations indicative of a difference in the rate of pure dephasing. The nine-water PBC calculation was also used to calculate the wavenumber shifts observed in the water isotopomers.     

Spectroscopy and predissociation of the 3A2 electronic state of ozone 16O3 and 18O3 by high resolution Fourier transform spectrometry

A high resolution Fourier transform spectrometry analysis of the rotational structure of the 2(0)1 absorption bands of the 3A2<--X1A1 Wulf transition for the isotopomers 16O3 and 18O3 of the ozone molecule is presented. These bands are very intense compared to the 0(0)0 bands but the predissociation is so strong that the main sub-bands appear as continuous contours. Isolated lines and band contour methods are used together to analyse these two rovibrational bands. The lines corresponding to the F2 component are generally the most intense and isolated. Our data sets for the (0 1 0) level of the 3A2 state are limited to about 102 weakly or unperturbed rotational lines for the 2(0)1 of 16O3 in the range 9620-10,140 cm(-1) and 123 weakly or unperturbed rotational lines for the same band of 18O3. Using for each of them the well-defined ground state parameters, we obtained a standard deviation of about 0.035 cm(-1) in the fit to the lines for 16O3 and 0.027 cm(-1) in the case of 18O3. The rotational constants A, B and C, the three rotational distortion terms deltaK, deltaJK and deltaJ, the spin-rotation constants a0, a and b have been successfully calculated for 16O3 and 18O3 while the spin-spin constants were fixed to their respective values obtained for the origin bands. As is the case for the 0(0)0 band, we have a partial agreement with the isotopic laws for the rotational constants. The geometrical parameters of the (0 1 0) level of 3A2 state for the two isotopomers are close, r = 1.357 A, theta = 100.7 degrees for 18O3 and r = 1.352 A and theta = 100.0 degrees for 16O3. The origin of the 2(0)1 band of 18O3 is red shifted by 7.06(4) cm(-1) with respect to 16O3 2(0)1 band and the two bending mode quanta are, respectively, 528.99(9) and 501.34(7) cm(-1). A preliminary qualitative analysis of the predissociation is given in the particular case of the F2 spin component of 16O3 for 0(0)0 and 2(0)1 bands by the measurement of shifts of positions of some rovibrational levels and the evolution of predissociation broadenings in (Q)Q2 branches. We justify the existence of perturbations in the rovibrational levels of 3A2 state through different interaction types: with the dissociation continuum of the same electronic state or with high vibrational repulsive or weakly bound levels of the ground state.