The nu(1) and nu(3) Bands of the (17)O(16)O(17)O Isotopomer of Ozone

Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O-enriched ozone sample, an extensive analysis of the nu(3) band together with a partial identification of the nu(1) band of the (17)O(16)O(17)O isotopomer of ozone has been performed for the first time. As for other C(2v)-type ozone isotopomers [J.-M. Flaud and R. Bacis, Spectrochim. Acta, Part A 54, 3-16 (1998)], the (001) rotational levels are involved in a Coriolis-type resonance with the levels of the (100) vibrational state. The experimental rotational levels of the (001) and (100) vibrational states have been satisfactorily reproduced using a Hamiltonian matrix which takes into account the observed rovibrational resonances. In this way precise vibrational energies and rotational and coupling constants were deduced and the following band centers nu(0)(nu(3)) = 1030.0946 cm(-1) and nu(0)(nu(1)) = 1086.7490 cm(-1) were obtained for the nu(3) and nu(1) bands, respectively. Copyright 2000 Academic Press.     

The nu(2) Band of Formaldehyde-d(2)

High-resolution Fourier transform infrared spectrum of the nu(2) band (1590-1780 cm(-1)) of deuterated formaldehyde D(2)CO has been recorded. More than 2500 rovibrational transitions have been assigned up to J(max) = 52 and K(max)(a) = 17. The upper state v(2) = 1 (A(1)) was found to be perturbed by a DeltaK(a) = 2 interaction with the v(4) = 2 (A(1)) state. To explain the resonance perturbation in the v(2) = 1 state, some lines of the 2nu(4) band (the band center at about 1868 cm(-1)) have also been assigned. Both bands were fitted simultaneously to the Watson-type rotational Hamiltonian using I(r) representation in A reduction, and the mutual interaction was taken into account. As a result, the rotational parameters of the v(2) = 1 state up to eighth order and the interaction parameter have been obtained. Copyright 2001 Academic Press.     

Absolute Intensities Measurements in the nu(4) + nu(5) Band of (12)C(2)H(2): Analysis of Herman-Wallis Effects and Forbidden Transitions

We measured absolute line intensities in two bands of (12)C(2)H(2) near 7.5 μm, namely the nu(4) + nu(5)(Sigma(+)(u))-0(Sigma(+)(g)) and nu(4) + nu(5)(Delta(u))-0(Sigma(+)(g)) bands, using Fourier transform spectroscopy with an accuracy estimated to be better than 2%. Using theoretical predictions from Watson [J. K. G. Watson, J. Mol. Spectrosc. 188, 78 (1998)], the observation of the forbidden nu(4) + nu(5)(Delta(u))-0(Sigma(+)(g)) band and the Herman-Wallis behavior exhibited by its rotational lines were studied quantitatively in terms of two types of interactions affecting the levels involved by the band: l-type resonance and Coriolis interaction. In the case of the nu(4) + nu(5)(Sigma(+)(u))-0(Sigma(+)(g)) band, the influence of l-type resonance is also confirmed. We also attributed the intensity asymmetry observed between the R and P branches of that latter band to a Coriolis interaction with l = 1 levels. We did not observe the nu(4) + nu(5)(Sigma(-)(u))-0(Sigma(+)(g)) band, consisting only of a Q branch, in agreement with Watson's prediction. Copyright 2000 Academic Press.     

High-Resolution Infrared and Millimeter-Wave Study of the Fermi-Coupled v(2) = 1 and v(3) = 2 States of DSiF(3)

The nu(2) (nu(eff.) 854.841 cm(-1)) and 2nu(3) infrared bands (nu(eff.) 840.083 cm(-1)) of DSiF(3) have been studied with a resolution of 2.5 x 10(-3) cm(-1). Moreover, millimeter-wave transitions in the v(2) = 1 and v(3) = 2 states up to J" = 33 have been measured. The assignments and fit of the poorly resolved, compressed cluster-type 2nu(3) IR transitions have been confirmed by a simultaneous study of the 2nu(3)-nu(3) band. The constant W = 5.116 cm(-1) of the Fermi interaction between the v(2) = 1 and v(3) = 2 levels has been determined from frequency effects which are in agreement with relative intensities of the nu(2) and 2nu(3) bands. The deperturbed (B(0) - B(v)) and (C(0) - C(v)) values of the states involved agree with their ab initio predictions within 7% in the worst case. Copyright 2001 Academic Press.     

High-Resolution Infrared Spectrum of CD(3)CN: Analysis of the Interacting nu(3) and nu(6) Bands and Evaluation of the A(0) Constant

The infrared spectrum in the range 900-1230 cm(-1) including the fundamental bands nu(3) and nu(6) of CD(3)CN 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 nu(6) band. For the weak nu(3) 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 nu(3)/nu(6) Coriolis resonance. There is also an l(1,-2) resonance between nu(3) and nu(6), which made it possible to obtain a value 2.647721(50) cm(-1) for the axial rotational constant A(0), when D(0)(K) from force field calculations was applied. Different types of resonances with the overtone 3nu(8) and the combinations nu(4)+nu(8) and nu(7)+nu(8) were observed. A fit with a standard deviation of 0.0019 cm(-1) was attained by using a model of 10 different resonances. Copyright 2001 Academic Press.     

High-Resolution Absorption Spectroscopy of the 3nu(1) and 3nu(1) + nu(3) Bands of Propyne

The 3nu(1) and 3nu(1) + nu(3) bands of propyne have been recorded at Doppler-limited resolution by Fourier transform spectroscopy and intracavity laser absorption spectroscopy, respectively. The two bands show a mostly unperturbed J rotational structure for each individual K subband. However, as a rule the K structure ordering is perturbed in overtone transitions of propyne and different effective parameters associated with each K subband have been determined. From the vibrational energy levels, a value of -6.6 cm(-1) has been obtained for the x(13) cross anharmonicity in perfect agreement with the origins of the nu(1) + nu(3) and 2nu(1) + nu(3) combination bands estimated from the FTIR spectrum. Hot bands from the v(9) = 1 and v(10) = 1 levels associated with the 3nu(1) + nu(3) combination band have been partly rotationally analyzed and the retrieved values of x(39) and x(3,10) are in good agreement with literature values. Finally, the 4nu(1) + nu(9) - nu(9) band centered at 12 636.6 cm(-1) has been recorded by ICLAS. The red shift of this hot band relative to 4nu(1) and the DeltaB(v) value are discussed in relation to the anharmonic interaction between the 4nu(1) and 3nu(1) + nu(3) + nu(5) levels. Copyright 2000 Academic Press.     

High-Resolution Study of the First Hexad of D(2)O

The high-resolution Fourier transform spectra of the D(2)O molecule have been recorded and assigned in the 4200-5700 cm(-1) region where the vibration-rotation bands 2nu(1), 2nu(3), nu(1) + nu(3), nu(1) + 2nu(2), 2nu(2) + nu(3), and 4nu(2) are located. The presence of numerous and very strong accidental perturbations between the states of the hexad makes it necessary to take into account not only ordinary resonance interactions of the Fermi, Darling-Dennison, and/or Coriolis types, but interactions between the states (v(1)v(2)v(3)) and (v(1) -/+ 2v(2) +/- 2v(3) +/- 1) as well. Parameters of all six vibrational states of the hexad were obtained from the fit of experimental energy values. Copyright 2000 Academic Press.     

Line-Mixing Effects in He- and N(2)-Broadened Sigma <-- Pi Infrared Q Branches of C(2)H(2)

Two Q branches of C(2)H(2) near 716.3 and 719.9 cm(-1) belonging to the (nu(4) + nu(5))(0) - nu(1f)(4) and 2nu(0)(5)-nu(1f)(5) bands, of Sigma <-- Pi symmetry, have been studied for He and N(2) perturbers at pressures ranging from 0.05 to 1 atm, using a tunable diode-laser spectrometer. To interpret the line-mixing effects observed in these spectra, we have applied a model based on the energy-corrected sudden approximation whose parameters have been only derived from line-broadening data. This model provides satisfactory agreement with experimental bandshapes for both bands and perturbers, especially at pressures higher than 0.1 atm. The Q-branch profiles for C(2)H(2)-He are higher and narrower than those obtained for C(2)H(2)-N(2) at the same pressure as the result of smaller broadening coefficients and larger line-mixing effects in the former system. Copyright 2000 Academic Press.     

High-Resolution Infrared Study of the nu(7), nu(8), and nu(15) Bands and Millimeter-Wave Investigation of the v(8) = 1 State of CF(2)Cl-CH(3)

High-resolution (Deltavarsigma = 2.3 and 2.9 x 10(-3) cm(-1)) FTIR spectra of natural and (35)Cl monoisotopic CH(3)CF(2)Cl have been recorded at -70 degrees C in the 600-1400 cm(-1) range. The bands nu(7), nu(8), and nu(15) have been rotationally analyzed for both isotopic varieties. With the help of predictions based on nu(8) parameters, the millimeter-wave spectrum of the (35)Cl species in the v(8) = 1 state has been observed and jointly fitted with the IR data. Only a small number of local perturbations have been detected in the spectra. Altogether more than 8000 IR transitions have been fitted with an experimental precision of ca. 3 x 10(-4) cm(-1). Copyright 2000 Academic Press.     

High-Resolution Infrared Spectrum of the Ring-Puckering Band, nu(10), of Diborane

The spectrum of the nu(10) band of diborane, arising from the ring-puckering vibration, has been obtained with a spectral resolution of 0.0015 cm(-1) in the region 275-400 cm(-1). The spectrum of a sample enriched in (10)B was recorded as well as one with naturally abundant boron, i.e., 64% (11)B(2)H(6), 32% (10)B(11)BH(6), and 4% (10)B(2)H(6). This mode is the lowest vibrational level of the molecule and is unperturbed, allowing a complete assignment of not only the fundamental bands but also the 2nu(10)-nu(10) hot bands of all three boron isotopomers. The intensities of several hundred lines of the fundamental and hot bands of all isotopomers have been measured and vibrational transition moments have been obtained. Finally, it has been shown that the harmonic approximation does not apply for nu(10). Copyright 2000 Academic Press.     

Rovibrational Analysis of the nu(2) Band of Diazirine-d(2)

The gas-phase IR spectrum of the nu(2) (A(1), 1610.33 cm(-1)) band of the deuterated isotopomer of diazirine, D(2)CN(2), a three-membered ring compound which belongs to the molecular symmetry point group C(2v), has been studied at a resolution of about 0.005 cm(-1). This vibrational mode which can be approximately described as N&dbond;N stretching is widely perturbed. This is due to various interactions with the tetrad consisting of the binary combinations nu(6) + nu(7) (A(1)), nu(7) + nu(9) (A(2)), nu(5) + nu(6) (B(2)), and nu(5) + nu(9) (B(1)), which form a relatively isolated pentad together with nu(2) in the wavenumber region 1560-1610 cm(-1). A simultaneous upper state analysis of nu(2) from a pentad model including these resonances has been performed and a set of spectroscopic parameters has been obtained. Since the four combination bands of the pentad are dark states, only band centers could be determined; in addition for nu(5) + nu(9) and nu(7) + nu(9) also the term (B - C)/2 has been obtained. A number of Coriolis interaction constants and the vibrational resonance (with nu(6) + nu(7)) parameter have been calculated as well. Copyright 2001 Academic Press.     

High-Resolution Fourier Transform and Diode-Laser Spectroscopy of the nu(6) Fundamental of C(2)F(6) and Associated Hot Bands

High-resolution infrared spectra of the nu(6) (713 cm(-1)) band region of C(2)F(6) vapor have been recorded at several temperatures. Spectra at 77, 200, and 300 K were recorded using a Fourier transform spectrometer with unapodized resolutions of 0.0018 cm(-1) (200 and 300 K) and 0.008 cm(-1) (77 K). Spectra with rotational temperatures in the range 5-50 K were recorded in a supersonic jet using diode-laser absorption spectroscopy. The nu(6) band contains two clear sequences of hot-bands: one arises from the nu(4) torsional vibration at 67.5 cm(-1); the other, shorter, weaker progression is built on the doubly degenerate nu(9) vibration at 220 cm(-1). They lie to high and low wavenumbers of the fundamental band, respectively. Eleven series were assigned and fitted to these hot bands. A perturbed series in the nu(4) sequence is considered, by analogy with the infrared spectrum of C(2)H(6) vapor, to be caused by an xy-Coriolis interaction either between 5nu(4) and nu(9) + 2nu(4) in the ground state or, in the upper state, nu(6) + 5nu(4) with nu(6) + nu(9) + 2nu(4) or nu(6) + 5nu(4) with 2nu(8). One further series resolved only in the jet spectrum and lying very close to the fundamental is almost certainly due to the nu(6) fundamental of the isotopomer (13)C(12)CF(6). Copyright 2000 Academic Press.     

13C(16)O(2): Global Treatment of Vibrational-Rotational Spectra and First Observation of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) Absorption Bands

The effective operator approach is applied to the calculation of both line positions and line intensities of the (13)C(16)O(2) molecule. About 11 000 observed line positions of (13)C(16)O(2) selected from the literature have been used to derive 84 parameters of a reduced effective Hamiltonian globally describing all known vibrational-rotational energy levels in the ground electronic state. The standard deviation of the fit is 0.0015 cm(-1). The eigenfunctions of this effective Hamiltonian have then been used in fittings of parameters of an effective dipole-moment operator to more than 600 observed line intensities of the cold and hot bands covering the nu(2) and 3nu(2) regions. The standard deviations of the fits are 3.2 and 12.0% for these regions, respectively. The quality of the fittings and the extrapolation properties of the fitted parameters are discussed. A comparison of calculated line parameters with those provided by the HITRAN database is given. Finally, the first observations of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) absorption bands by means of photoacoustic spectroscopy (PAS) is presented. The deviations of predicted line positions from observed ones is found to be less than 0.1 cm(-1), and most of them lie within the experimental accuracy (0.007 cm(-1)) once the observed line positions are included in the global fit. Copyright 2000 Academic Press.     

Experimental and Theoretical Study of the Electronic States and Spectra of TeH and TeLi

Gas-phase emission spectra of the hitherto unknown free radical TeLi have been measured in the NIR range with a Fourier-transform spectrometer. The emissions were observed from a fast flow system in which tellurium vapor in argon carrier gas was passed through a microwave discharge and mixed with lithium vapor in an observation tube. Two systems of blue-degraded bands were measured at high spectral resolution in the ranges 8000-9000 and 5700-6700 cm(-1) and vibrational and rotational analyses were performed. In order to aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of TeLi and the isovalent TeH and also electric dipole transition moments connecting them. As in the TeH system, the ground state of TeLi is found to be X(2)Pi(i), but with a remarkably smaller spin-orbit splitting. The TeLi calculations indicate a strongly bound A(2)Sigma(+) state, while in TeH the analogous state is computed to lie significantly higher at approximately 32 000 cm(-1), and it is strongly predissociated. Based on the theoretical analysis, the observed TeLi band systems are assigned to the transitions A(2)Sigma(+)(A1/2)-->X(1)(2)Pi(3/2)(X(1)3/2) and A(2)Sigma(+)(A1/2)-->X(2)(2)Pi(1/2)(X(2)1/2). Analysis of the spectra has yielded the molecular constants (in cm(-1)) X(1)(2)Pi(3/2):omega(e)=457.49(3), omega(e)x(e)=2.482(9), B(0)=0.408908(8); X(2)(2)Pi(1/2): T(e)=2353.44(3), omega(e)=456.28(4), omega(e)x(e)=2.635(8), B(0)=0.414954(8), p(0)=1.00637(4); A(2)Sigma(+): T(e)=8574.64(2), omega(e)=437.81(3), omega(e)x(e)=2.581(8), B(0)=0.423903(8), p(0)=-0.19915(2), where the numbers in parentheses are the standard deviations of the parameters. Comparison of the isovalent TeLi and TeH systems emphasizes that the difference in bonding character (ionic in TeLi vs covalent in TeH) is responsible for qualitative differences in the electronic spectra of these two molecules. Copyright 2001 Academic Press.     

High-Resolution Laser Photoacoustic Spectroscopy of HSiF(3): The 5nu(1) and 6nu(1) Overtone Bands

A spectrum of HSiF(3) has been recorded at room temperature with a gas pressure of 20-50 Torr in the near-infrared region. A laser photoacoustic spectrometer consisting of a longitudinal resonant cell coupled to a titanium:sapphire ring laser was employed. The 5nu(1) and 6nu(1) overtone bands of H(28)SiF(3) associated with the Si-H stretching have been observed at high resolution (3 x 10(-2) cm(-1)) in the regions 10 900-10 960 and 12 875-12 925 cm(-1), respectively. About 450 lines of the 5nu(1)-0 band have been assigned (J 相似文献   

High-Resolution Spectrum and Rovibrational Analysis of the nu(2)/nu(5) Dyad of D(3)SiF near 700 cm(-1)

The nu(2) (A(1), 710.157 cm(-1)) and nu(5) (E, 701.717 cm(-1)) fundamental bands of D(3)(28)SiF have been studied by FTIR spectroscopy with a resolution of 2.4 x 10(-3) cm(-1). We assigned 1648 lines for the parallel band (J(max) = 50, K(max) = 21), 4279 for the perpendicular band (J(max) = 52, K(max) = 27), and in addition 671 perturbation-allowed transitions (J(max) = 50, K(max) = 12). The nearly degenerate v(2) = 1 and v(5) = 1 states are linked by (DeltaK = +/-1, Deltal = +/-1) and (DeltaK = +/-2, Deltal = -/+1) interactions, while the l(5) = +/-1 levels of nu(5) interact also by l(2, -1), l(2, 2), and l(2, -4) interactions. The first model with 36 free parameters, taking into account all these resonances through a nonlinear least-squares program, gave standard deviations of 1.56 x 10(-4) cm(-1) for 5997 nonzero-weighted IR data and 138 kHz for 8 MW data from the literature. The second model, in which the main Coriolis term was constrained to a force field value, used 37 parameters and gave similar standard deviations. A new determination of the A(0) and D(0)(K) ground state parameters was performed by two methods: either using differences between "forbidden" transitions differing by 3 in K or letting A(0) and D(0)(K) free in the global fit. The values obtained are fully compatible with those obtained previously by the "loop method." Copyright 2000 Academic Press.     

The nu(2), nu(4) + nu(5), nu(6) + nu(9), and nu(8) Band System in 1,1,1-Trifluoroethane

High-resolution FTIR spectra of 1,1,1-trifluoroethane (HFC-143a) have been recorded in the region from 1370 to 1470 cm(-1) with an unapodized resolution of 0.0016 cm(-1) at room temperature and of 0.004 cm(-1) at 183 and 100 K. The two main infrared active bands of A(1) symmetry have been shown to be nu(2) at 1407.5 cm(-1) and nu(4) + nu(5) at 1440.5 cm(-1). With the aid of Raman spectra, the two infrared inactive bands of E symmetry in this spectra region have been shown to be nu(8) at 1457.5 cm(-1) and nu(6) + nu(9) at 1446.2 cm(-1). The nu(2) band was analyzed as an isolated band, whereas the nu(4) + nu(5) band was analyzed as part of the triad nu(4) + nu(5), nu(6) + nu(9), and nu(8). Copyright 2000 Academic Press.     

High-Resolution Study of the Mid-Infrared Region of FNO(2)

Of the gas-phase IR spectrum of nitrylfluoride, FNO(2), between 1200 and 1900 cm(-1), the bands nu(4), 2nu(6), nu(2) + nu(3), and nu(1) have been studied at a resolution of ca. 0.003 cm(-1). Improved ground state rotational and centrifugal distortion constants have been obtained from a simultaneous analysis of the data from F. Hegelund, H. Bürger, and G. Pawelke [J. Mol. Spectrosc. 184, 350-361 (1997)] and the present data from nu(4) and nu(1). The nu(4) and 2nu(6) bands are free from local perturbations, and upper state spectroscopic constants have been obtained from the conventional Watson Hamiltonian. The bands nu(1) and nu(2) + nu(3) are strongly perturbed by Coriolis interactions with the nearby dark levels nu(5) + nu(6), nu(3) + nu(6), and nu(2) + nu(5). Upper state constants for nu(1) and nu(2) + nu(3) are obtained from triad and tetrad models, respectively, including Coriolis resonances within this system. In addition Coriolis interaction parameters and the vibrational energies for the three dark states together with some of their rotational constants are determined from the observed perturbation effects on nu(1) and nu(2) + nu(3). Copyright 2000 Academic Press.     

Rovibrational Study of the CH(2) Wagging Fundamental of Monofluoroacetonitrile

The vapor-phase infrared spectrum of monofluoroacetonitrile (CH(2)FCN) has been recorded at high resolution in the nu(4) band region (1363-1398 cm(-1)) using a tunable diode laser spectrometer. A detailed assignment of the rotational structure of the expected a-/b-hybrid band has been made for a-type transitions with K(a)相似文献   

First High-Resolution Infrared Observation of the Symmetry-Forbidden nu(5) Band of (10)B(2)H(6)

Spectra of (10)B monoisotopic diborane, B(2)H(6), have been recorded at high resolution (2-3 x 10(-3) cm(-1)) by means of Fourier transform spectroscopy in the region 700-1300 cm(-1). A thorough analysis of the nu(18) a-type, nu(14) c-type, and nu(5) symmetry-forbidden band has been performed. Of particular interest are the results concerning the nu(5) symmetry-forbidden band, which is observed only because it borrows intensity through an a-type Coriolis interaction with the very strong nu(18) infrared band located approximately 350 cm(-1) higher in wavenumber. The nu(5) band has been observed around 833 cm(-1) and consists of a well-resolved Q branch accompanied by weaker P- and R-branch lines. Very anomalous line intensities are seen, with the low K(a) transitions being vanishingly weak, and Raman-like selection rules observed. The determination of the upper state Hamiltonian constants proved to be difficult since the corresponding energy levels of each of the bands are strongly perturbed by nearby dark states. To account for these strong localized resonances, it was necessary to introduce the relevant interacting terms in the Hamiltonian. As a result the upper state energy levels were calculated satisfactorily, and precise vibrational energies and rotational and coupling constants were determined. In particular the following band centers were derived: nu(0) (nu(5)) = 832.8496(70) cm(-1), nu(0) (nu(14)) = 977.57843(70) cm(-1), and nu(0) (nu(18)) = 1178.6346(40) cm(-1). (Type A standard uncertainties (1varsigma) are given in parentheses.) Copyright 2000 Academic Press.