Fundamental Ν3 Research Articles

The ν2+ν4 Band of Carbonyl Fluoride

We have measured and fitted over 600 lines in the ν2+ν4 combination band of COF2. The spectrum is well reproduced by extrapolation of rotational constants from the ν2 and ν4 fundamentals, with no evidence of significant perturbation. The band centre of 2195.272 15(11) cm−1 permits an estimate of −11.32 cm−1 for the anharmonicity constant x24.

High-Resolution Infrared Spectrum of PH2Br: Rotational Analysis of the ν3 and ν4 Bands

The infrared spectrum of short-lived PH2Br has been observed by studying the reaction of P2H4 with gaseous HBr. The a-type fundamental bands ν3 at 812 cm−1 and ν4 at 399 cm−1 have been recorded with a resolution of ca. 5×10−3 cm−1, and their rotational fine structure has been observed. While the ν4 band and its hot band 2ν4−ν4 associated with the P–Br stretching reveal compact qP and qRJ-clusters, the HPBr bending fundamental ν3 shows a widely dispersed structure. A c-type Coriolis interaction of ν3 (Ka) with the unobserved ν6 state (Ka+1) at 795 cm−1, with resonance between Ka=1 and 2, was detected and analyzed. Comparison with results of ab initio calculations revealed in general excellent agreement.

Rotationally resolved infrared spectroscopy of h2- and d1-formic acid monomer in liquid He droplets

Rotationally resolved spectra of h2- and d1-formic acid embedded in liquid helium droplets have been recorded in the spectral region of the O–H (ν1) and C–H (ν2) stretch vibrations. Accidental resonant mixing between the ν1-band of h2-formic acid and the combination bands (ν2+ν7) and (ν2+ν9) has been observed. The fundamental ν1 band can interact via Fermi resonance with the (ν2+ν7), and the (ν2+ν7) via Coriolis coupling with the (ν2+ν9) band. Examination of the resonance induced line-broadening effects suggests that the helium environment modifies vibrational relaxation dynamics. The 2ν3 C=O stretch overtone is also observed and was assigned by a density functional theory (DFT) ab initio calculation. The spectroscopic constants are determined by fitting all spectra with a standard gas phase Hamiltonian.

Infrared spectra of C(3)H(3)(+)-N(2) dimers: identification of proton-bound c-C(3)H(3)(+)-N(2) and H(2)CCCH(+)-N(2) isomers.

Mid-infrared photodissociation spectra of mass selected C(3)H(3)(+)-N(2) ionic complexes are obtained in the vicinity of the C-H stretch fundamentals (2970-3370 cm(-1)). The C(3)H(3)(+)-N(2) dimers are produced in an electron impact cluster ion source by supersonically expanding a gas mixture of allene, N(2), and Ar. Rovibrational analysis of the spectra demonstrates that (at least) two C(3)H(3)(+) isomers are produced in the employed ion source, namely the cyclopropenyl (c-C(3)H(3)(+)) and the propargyl (H(2)CCCH(+)) cations. This observation is the first spectroscopic detection of the important c-C(3)H(3)(+) ion in the gas phase. Both C(3)H(3)(+) cations form intermolecular proton bonds to the N(2) ligand with a linear -C-H...N-N configuration, leading to planar C(3)H(3)(+)-N(2) structures with C(2v) symmetry. The strongest absorption of the H(2)CCCH(+)-N(2) dimer in the spectral range investigated corresponds to the acetylenic C-H stretch fundamental (v(1) = 3139 cm(-1)), which experiences a large red shift upon N(2) complexation (Delta(v1) approximately -180 cm(-1)). For c-C(3)H(3)(+)-N(2), the strongly IR active degenerate antisymmetric stretch vibration (v4)) of c-C(3)H(3)(+) is split into two components upon complexation with N(2): v4)(a(1)) = 3094 cm(-1) and v4)(b(2)) = 3129 cm(-1). These values bracket the yet unknown v4) frequency of free c-C(3)H(3)(+) in the gas phase, which is estimated as 3125 +/- 4 cm(-1) by comparison with theoretical data. Analysis of the nuclear spin statistical weights and A rotational constants of H(2)CCCH(+)-N(2) and c-C(3)H(3)(+)-N(2) provide for the first time high-resolution spectroscopic evidence that H(2)CCCH(+) and c-C(3)H(3)(+) are planar ions with C(2v) and D(3h) symmetry, respectively. Ab initio calculations at the MP2(full)/6-311G(2df,2pd) level confirm the given assignments and predict intermolecular separations of R(e) = 2.1772 and 2.0916 A and binding energies of D(e) = 1227 and 1373 cm(-1) for the H-bound c-C(3)H(3)(+)-N(2) and H(2)CCCH(+)-N(2) dimers, respectively.

In situ Raman spectroscopic studies of trimethylindium pyrolysis in an OMVPE reactor

An in situ investigation of thermal decomposition reactions of trimethylindium (TMIn) in a vertical, upflow chemical vapor deposition reactor has been carried out using Raman spectroscopy. Monomethylindium (MMIn) and atomic indium were detected along with the precursor TMIn using N2 as the carrier gas. Atomic indium was identified by the peak at 2215 cm−1, which is equal to the difference between two spin–orbit split levels of atomic indium in the ground electronic state. The multiple peaks corresponding to MMIn, which were enhanced by a resonance Raman effect, consisted of fundamentals(ν2 = 1097 cm−1,ν3 = 430 cm−1,ν5 = 1364 cm−1, ν6 = 696 cm−1) and a high progression of overtones and combination bands. Concentration profiles were obtained from the measurements of peak intensities of TMIn, MMIn, and indium at different distances away from the hot susceptor along the vertical centerline of the reactor.

High-Resolution Infrared Spectra of the ν2, ν3, ν4, and 2ν3 Bands of 32S16O3

New measurements are reported for the infrared spectrum of sulfur trioxide, 32S16O3, with resolutions ranging from 0.0015 cm−1 to 0.0025 cm−1. Rovibrational constants have been measured for the fundamentals ν2, ν3, and ν4 and the overtone band 2ν3. Comparisons are made with the earlier high-resolution measurements on SO3, and the high correlation among some of the constants related to the Coriolis coupling of the ν2 and ν4 levels is discussed in order to understand the areas of disagreement with the earlier work. Splittings of some of the levels are observed and the splitting constant for K=3 of the ground state is determined for the first time. Other observed splittings include the K=1 levels of 2ν3 (l=2), the K=2 levels of ν3 and ν4, and the K=3 levels of ν2. The analysis shows that there are level crossings between the l=0 and l=2 states of 2ν3 that allow one to determine the separation of the subband centers for these two states even though access to the l=0 state from the ground state is electric-dipole forbidden. This is a generalized phenomenon that should be found for many other molecules with the same symmetry. The l-type resonance constant, q3, that causes the splitting of the l3=±1, k=±1 levels of ν3 also couples the l3=0 and 2 states of 2ν3.

High precision rovibrational and hyperfine analysis of the v4=1 level of bromochlorofluoromethane

We performed a ultra high resolution infrared spectroscopic analysis of the CF-stretching fundamental ν4 of CHFClBr at 9.4μm. The saturated absorption spectra of the hyperfine structures of many rovibrational transitions of its two more abundant isotopomers were recorded with our high resolution CO2 laser-based spectrometer. This led to the determination of the complete quadrupole coupling tensors of the 3/2 nuclear spins of the bromine and the chlorine in the v4=1 level, which allow the prediction of the hyperfine structure of any rovibrational line with an accuracy of a few kHz. By studying the isotopic dependence of these molecular constants, the quadrupole coupling tensors of two other isotopomers were extrapolated. We also report promising preliminary results of the determination of the rotational and centrifugal distortion constants of the same vibrational level.

First High-Resolution Analysis of the Six Fundamental Bands ν1, ν2, ν3, ν4, ν5, and ν6 of COF35Cl in the 340- to 2000-cm−1 Region

Concern about the implication of chlorofluorocarbons (CFCs) in atmospheric ozone depletion has led to numerous measurements of the concentrations of halogen-containing compounds in the stratosphere. Of the various possible oxidation products of CFC's in the stratosphere, carbonyl chlorofluoride (COFCl) may receive special attention. High-resolution atmospheric infrared spectra are potential means of monitoring COFCl. However, there is little information on the spectroscopy of this molecule in the literature. We have therefore recorded spectra of pure 35Cl-enriched and natural samples of COFCl at ≤0.0033 cm−1 resolution with the BRUKER Fourier transform spectrometer at the University of Wuppertal. We present here the first high-resolution analysis of the six fundamental bands ν1 (CO stretching mode), ν2 (C–F stretching mode), ν3 (C–Cl stretching mode), ν4 (CFCl bending mode), ν5 (CFCl rocking mode), and ν6 (out of plane bending mode) located at 1875.8256, 1095.0646, 764.3876, 501.5941, 408.8099, and 666.5862 cm−1, respectively, for the COF35Cl isotopic species of carbonyl chlorofluoride. The ν3, ν4, ν5, and ν6 bands which are mainly of A-type, B-type, B-type, and C-type, respectively, appear as unperturbed. On the other hand, both the ν1 and ν2 bands have a hybrid character (with both A- and B-type transitions), and the analysis of these two bands was complicated by numerous resonances. Excellent results are obtained for the unperturbed ν3–ν6 bands and for the perturbed ν2 band, but for the ν1 band, the resonance scheme of which is more complex, the results of the analysis are slightly less satisfactory.

Diode Laser Jet Spectra and Analysis of the ν3 and ν8 Fundamentals of CHF2Cl

High-resolution infrared spectra have been measured for mixtures of CHF2Cl in Ne, expanded in a supersonic planar jet. We present the analysis for the ν3 and ν8 fundamentals of CHF235Cl and CHF237Cl.

Infrared studies of CO2 doped Xe solutions in gas, liquid and solid phases. The fundamental ν3 band and the Coriolis perturbed Fermi doublet (ν1+ν21, ν1+ν211)

The IR absorption spectra of CO2 doped Xe solutions have been recorded in the range of the fundamental ν3(Σu) band and of the Coriolis perturbed ν1+ν21, ν1+ν211(πu) Fermi doublet (ν1+ν2≈3ν2) in gas, liquid and solid phases. The characteristic transformation and rapid narrowing of the ν3 band, observed in the gas to liquid phase transition, shows marked hindering of the rotational motion of the CO2 molecule in dense Xe mixtures. It was found that the liquid to solid phase transition is accompanied by noticeable broadening of the ν3 band. The rotational motion of CO2 is not frozen in solid Xe at least near the freezing point. This is in contrast with sharp narrowing of the vibrational bands and so with blocking up rotations in the case of a heavier CS2 guest in the solid Xe host just below the freezing point. The intensity ratio A(ν1+ν21)/A(ν1+ν211) of the Coriolis perturbed ν1+ν21, ν1+ν211 doublet reveals the noticeable increase from 8±1 in a low density gas to 18±2 in the liquid phase. The results obtained suggest remarkable modification of the second-order Coriolis coupling in the case of CO2 doped dense liquid Xe.

Vibrational Spectra of Nickel and Platinum Dioxide Molecules Isolated in Solid Argon

The reactions of two group 10 metal atoms, nickel and platinum, with oxygen molecules at low temperature in solid argon have been reinvestigated. New information has been gathered on the interactions between transition metals and oxygen, more precisely, on platinum and nickel superoxides and their insertion products. For Pt(O2) the low-frequency metal−ligand ν2 and ν3 fundamentals have been observed and derived harmonic potential constants are compared to those of Ni(O2). Interest will then be taken in the dioxide insertion products, their differences in bonding as well as their production mechanisms. The positions of all three fundamentals for OPtO and of the two IR-active vibrations for ONiO have been experimentally determined and are compared to recent ab initio predictions.

Diode-Laser Measurements of Absolute Line Intensities in the ν1 Band of Cyanogen Chloride

With a tunable diode-laser spectrometer, absolute line intensity measurements have been made in the spectrum of cyanogen chloride in the vicinity of 710 cm−1. The intensity of the fundamental ν1 band has been found to be 6.088 cm−2 atm−1 for the 35ClCN isotopomer and 7.121 cm−2 atm−1 for the 37ClCN form. The influence of the Fermi resonance on the band intensity has been analyzed.

On the Empirical Determination of Some Harmonic and Anharmonic Force Constants in Benzene

In this work, the problem for the quality of empirically determined harmonic force constants in ground electronic state benzene has been carefully reexamined, for the case when strongly anharmonic vibrations are involved and in particular for the A1g (ν1 and ν2) vibrational system. A numerical procedure, based on a local bond Hamiltonian representation for the C−H stretch system and a symmetrized coordinate treatment for the ν1(C−C) mode, has been described and applied to the determination of the harmonic F1,1, F2,2, and F1,2, and some important (diagonal) anharmonic force constants, instead of the traditional FG analysis. As a reference data for the determination of the required force constants, the set of experimentally observed ν1 and ν2 fundamentals for four D6h benzene species C6H6, C6D6, 13C6H6, and 13C6D6 have been employed. The harmonic force constants as well as harmonic frequencies obtained in this work have substantial deviations from previous determinations. Using the presently determined forc...

High-Resolution Infrared Spectrum of CD3CN: Analysis of the Interacting ν3 and ν6 Bands and Evaluation of the A0 Constant

The infrared spectrum in the range 900–1230 cm−1 including the fundamental bands ν3 and ν6 of CD3CN has been studied. The resolution attained was 0.0025 cm−1 in the measurement on the Bruker 120 HR Fourier spectrometer in Oulu. About 4000 lines were assigned in the ν6 band. For the weak ν3 band, which has not been observed earlier directly, we were able to assign 206 lines in three subbands K=8–10. These lines become detectable due to the strong ν3/ν6 Coriolis resonance. There is also an ℓ(1,−2) resonance between ν3 and ν6, which made it possible to obtain a value 2.647721(50) cm−1 for the axial rotational constant A0, when D0K from force field calculations was applied. Different types of resonances with the overtone 3ν8 and the combinations ν4+ν8 and ν7+ν8 were observed. A fit with a standard deviation of 0.0019 cm−1 was attained by using a model of 10 different resonances.

High-Resolution Spectroscopy and Analysis of the ν3 and ν4 Fundamentals of Monoisotopic 70GeF4

The first high-resolution study on germanium tetrafluoride is reported. We used a monoisotopic sample of 70GeF4. The FTIR spectra of the two infrared active fundamentals, namely the ν4 (bending) and ν3 (stretching) modes, were recorded at a temperature of ca. 210 K and a resolution (1/maximum optical path difference) of 0.0031 and 0.0023 cm−1, respectively. These spectra were analyzed using the STDS software developed in Dijon. In both cases, we obtained a fit with a root mean square better than 1×10−3 cm−1. Both bands show very regular structures with no detectable perturbation.

Diode–Laser Jet Spectra and Analysis of the ν1 and ν4 Fundamentals of CCl3F

High-resolution infrared spectra have been measured for mixtures of CCl3F in Ne, expanded in a supersonic planar jet. We present the first analysis for the ν4 fundamental and a complete analysis for the ν1 band. Accurate spectroscopic constants have been obtained for both the ν1 fundamental of the most abundant isotopic species, C35Cl3F, C35Cl237ClF, and C35Cl37Cl2F. With respect to an earlier work [M. Snels, A. Beil, H. Hollenstein, M. Quack, U. Schmidt, and F. D'Amato, J. Chem. Phys. 103, 8846–8853 (1995)], the observation of Q branches of the three most abundant isotopomers allowed for an unambiguous determination of the ν1 band origins. The ν4 fundamental has not been the subject of a high-resolution analysis up to now. The observation of high-resolution spectra of the central part of the band permitted the determination of band origin, rotational constants, and Coriolis constant for the symmetric-top species, C35Cl3F.

Intermolecular potential energy surface of the proton-bound H2O+–He dimer: Ab initio calculations and IR spectra of the O–H stretch vibrations

Rotationally resolved infrared photodissociation spectra of the O–H stretch fundamentals (ν1 and ν3) of the H2O+–He open shell ionic complex have been recorded in the doublet electronic ground state. The analysis of the complexation-induced frequency shifts (Δν1 = − 15 cm−1, Δν3 = − 5.1 cm−1) and the rotational structure is consistent with a planar, translinear proton-bound H–O–H–He equilibrium geometry. The derived intermolecular H–He separation and O–H–He bond angle are R0 = 1.756(4) A and φ0 = 175(5)° in the ground vibrational state. The experimental results are in good agreement with the ab initio calculations performed at the unrestricted MP2 level using a basis set of aug-cc-pVTZ quality. The global minimum on the calculated potential energy surface features a slightly translinear proton-bound equilibrium geometry, with an intermolecular separation of Re = 1.6990 A, a bond angle of φe = 173.2°, dissociation energies of De = 425.9 cm−1 and D0 = 158.6 cm−1, and frequency shifts of Δν1 = − 34.4 cm−1 and Δν3 = − 11.6 cm−1. Tunneling splittings in the perpendicular component of the ν3 band are attributed to hindered internal rotation exchanging the two equivalent proton-bound structures ia a planar transition state with C2v symmetry. The calculated barrier for this internal motion amounts to Vb = 202.9 cm−1 and the dimer is closer to the semirigid limit than to free internal rotation. The interpretation of the H2O+–He spectrum is supported by the corresponding spectrum of the monodeuterated HOD+–He complex.

Experimental and theoretical CO2–Ar pressure-broadening cross sections and their temperature dependence

Line broadening coefficients of the CO2–Ar fundamental ν3 band are obtained experimentally and theoretically for temperatures from 120 to 765 K. The experimental results are obtained by Fourier-transform infrared spectroscopy. Theoretical values are provided ia quantum-mechanical (close coupling and coupled states) approaches as well as semiclassical (improved Smith–Giraud–Cooper and Robert–Bonamy) methods. The most up-to-date CO2–Ar ab initio intermolecular potential (J. M. Hutson, A. Ernesti, M. M. Law, C. F. Roche and R. J. Wheatley, J. Chem. Phys., 1996, 105, 9130) is employed for all calculations. For all the temperatures probed, theoretical values are found to be in a rather good agreement with experiment. In addition, the Raman Q(j) line broadening coefficients and the application of the random phase approximation are presented.

First overtone helium nanodroplet isolation spectroscopy of molecules bearing the acetylenic CH chromophore

High-resolution helium nanodroplet isolation spectra of the first overtone (2ν1) of the acetylenic stretch of several substituted acetylenes (RC≡C–H) at T=0.38 K, have been observed for the first time. A tunable 1.5 μm laser is coupled, using a power buildup cavity, to a beam of He droplets seeded with the molecule to be studied. Absorption spectra are recorded by monitoring the beam depletion as a function of laser frequency with a thermal detector. The spectra of hydrogen cyanide (HCN), monodeuteroacetylene (DCCH), cyanoacetylene (NCCCH), propyne (CH3CCH), trifluoropropyne (CF3CCH), 3,3-dimethylbutyne ((CH3)3CCCH), and trimethylsilylacetylene ((CH3)3SiCCH) have been recorded. Due to the superfluid nature of the droplet, rotational resolution is achieved despite the presence of some solvent-induced broadening. The spectroscopic constants have been extracted by means of spectral simulations. The resulting rotational constants are smaller than for the bare molecule by a factor which depends on the molecule nonsphericity and its gas-phase moment of inertia. The linewidths are found to be at least twice as large as those of the corresponding fundamental (ν1) transitions observed in a helium droplet by Nauta et al. [Faraday Discuss. Chem. Soc. 113, 261 (1999) and references therein]. The helium-induced spectral shifts are found to be very small, but cannot be easily rationalized.

The Near Degenerate ν3 and ν6 States of HSiD3 Revealing Δ(k − l) = 0, ±3, and ±6 Interactions

The infrared spectrum of HSiD3 has been recorded with a resolution of 3.3 × 10−3 cm−1 in the 600–775 cm−1 region. The fundamentals ν3 (A1), ν0 = 675.501 cm−1, and ν6 (E), ν0 = 682.687 cm−1 have been measured and rotationally assigned up to J′ = 30. Owing to the closeness of the band centers and the strength of the x, y-Coriolis interaction, ζy36 = 0.62, perturbations both of positions and intensities are strong. Since HSiD3 is an oblate top near the spherical top limit, the rotational energy level structure is such that numerous avoided crossings with Δ(k − l) = ±3 and ±6 are called forth by the Coriolis resonance. These give rise to “forbidden” transitions, 209 of which with J" and K" ≤ 30, and ΔK up to ±6, were observed. These enabled a significant improvement of the coefficients of the K-dependent ground state energy terms, C0 = 1.433 4268(12)cm−1, D0K = 2.851 6(57) × 10−6 cm−1, and H0K = −1.728(85) × 10−10 cm−1. Parameters of the v3 = 1 and v6 = 1 excited states were determined with two models corresponding to two different effective Hamiltonians. The model strictly obeying the constraints proposed by E. I. Lobodenko, O. N. Sulakshina, V. I. Perevalov, and V. G. Tyuterev (J. Mol. Spectrosc. 126, 159–170 (1987)) requires 45 adjustable parameters and fits the data with J ≥ 22 only poorly while, with an alternative model employing 44 free parameters, all data up to J′ = 30 were fitted with ς = 1.72 × 10−4 cm−1. A positive sign of the Coriolis intensity perturbation was found, and the transition moment ratio was determined, ‖M6:M3‖ = 0.70(5).