High-Resolution FTIR Spectrum of the nu(9) Band of Ethylene-D(4) (C(2)D(4))

The spectrum of the nu(9) fundamental band of ethylene-d(4) (C(2)D(4)) has been measured with an unapodized resolution of 0.004 cm(-1) in the frequency range of 2300-2400 cm(-1) using a Fourier transform infrared spectrometer. A total of 549 transitions have been assigned and fitted using a Watson's A-reduced Hamiltonian in the I(r) representation to derive rovibrational constants for the upper state (v(9) = 1) up to five quartic terms with a standard deviation of 0.00087 cm(-1). They represent the most accurate rovibrational constants for the nu(9) band so far. About 30 transitions of K(a)(') = 0, one transition of nu(9) which were identified to be perturbed possibly by the nearby nu(11) and nu(2) + nu(12) transitions, were not included in the final fit. The nu(9) band of C(2)D(4) was found to be basically B-type with an unperturbed band center at 2341.836 94 +/- 0.000 13 cm(-1). Copyright 2000 Academic Press.     

High-Resolution FTIR Spectrum of the nu(12) Band of trans-d(2)-Ethylene

The nu(12) band of trans-d(2)-ethylene (trans-C(2)H(2)D(2)) has been recorded with an unapodized resolution of 0.0024 cm(-1) in the frequency range of 1240-1360 cm(-1) by Fourier transform infrared (FTIR) spectroscopy. This band was found to be relatively free from any local frequency perturbations. By fitting a total of 1185 infrared transitions of nu(12) with a standard deviation of 0.00043 cm(-1) using a Watson's A-reduced Hamiltonian in the I(r) representation, a set of accurate rovibrational constants for v(12) = 1 state was derived. The nu(12) band is A type with a band center at 1298.03797 +/- 0.00004 cm(-1). Copyright 2000 Academic Press.     

Analysis of the nu(12) Band of Ethylene-(13)C(2) by High-Resolution FTIR Spectroscopy

The Fourier transform infrared (FTIR) spectrum of the nu(12) fundamental band of ethylene-(13)C(2) ((13)C(2)H(4)) was recorded with an unapodized resolution of 0.004 cm(-1) in the frequency range from 1380 to 1500 cm(-1). Rovibrational constants for the upper state (nu(12)=1) up to five quartic and three sextic centrifugal distortion terms were derived for the first time by assigning and fitting a total of 1177 infrared transitions using a Watson's A-reduced Hamiltonian in the I(r) representation. The rms deviation of the fit was 0.00045 cm(-1). The ground state rovibrational constants were also determined for the first time by a fit of 738 combination differences from the present infrared measurements, with a rms deviation of 0.00060 cm(-1). The A-type nu(12) band with a band center at 1436.65411+/-0.00005 cm(-1) was found to be relatively free from local frequency perturbations. The inertial defect Delta(12) was found to be 0.24300+/-0.00002 u?(2). Copyright 2001 Academic Press.     

The 3nu(2) Band of D(2)(16)O

The 3nu(2) overtone band of deuterium oxide, D(2)O, centered at 3474.3193 cm(-1), has been measured with high resolution in a 4-m base-length White cell attached to a Fourier transform spectrometer. The analysis of the spectrum led to the assignment of 347 transitions in this band, defining rovibrational energy levels in the (030) state up to K(a) = 7 for J as high as 9, and lower K(a) levels for J as high as 16. The (030) state was treated as an isolated state, following a Padé-Borel approximation in the effective Hamiltonian. Of the 115 energy levels included in the analysis, 80% were reproduced by the 21 adjusted parameters to within 0.0008 cm(-1), and the largest error was 0.0017 cm(-1). Copyright 2000 Academic Press.     

The High-Resolution Raman Spectrum of the nu4 Band of Diborane

The high-resolution Raman spectra of the nu4 bands of 11B2H6 and 11B10BH6 have been recorded and analyzed. The recordings have been made using a high-resolution spectrometer based on the inverse Raman effect. Q branches have been observed, but P and R branches were too weak to be seen, and simulations of the observed band contour have been necessary to complete the analysis. A weak Coriolis resonance with the 2nu10 level is present in the 11B2H6 spectrum. The band centers obtained are 790.9829(12) and 804.76985(27) cm-1 for 11B2H6 and 10B11BH6, respectively (uncertainties are type A with a coverage factor k = 1, i.e., 1 standard deviation). Copyright 1999 Academic Press.     

The High-Resolution FTIR Spectrum of the nu(1) Band of DOBr

Fourier transform infrared spectra of the nu(1) bands of DO(79)Br and DO(81)Br have been recorded with a resolution of 0.0055 cm(-1) in the frequency range of 2510-2800 cm(-1). A total of 1901 lines of the A/B hybrid-type bands of both isotopic species have been assigned and fitted to upper state rovibrational constants employing a Watson's S-reduced Hamiltonian up to sextic terms. The K(a) >/= 4 subband transitions were found to be perturbed and were not included in the fit. The unperturbed band centers for nu(1) of DO(79)Br and DO(81)Br are 2668.79211 +/- 0.00006 and 2668.78842 +/- 0.00005 cm(-1), respectively. The ratio of the vibrational dipole transition moments (μ(a):μ(b)) was found to be 1.30 +/- 0.04 for the band. Copyright 2000 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 Spectroscopy and Analysis of the nu(3) and nu(4) Fundamentals of Monoisotopic (70)GeF(4)

The first high-resolution study on germanium tetrafluoride is reported. We used a monoisotopic sample of (70)GeF(4). The FTIR spectra of the two infrared active fundamentals, namely the nu(4) (bending) and nu(3) (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 1x10(-3) cm(-1). Both bands show very regular structures with no detectable perturbation. Copyright 2001 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 Infrared Spectrum of BrCN in the nu(2) and nu(1)/2nu(2) Regions

The vibrational excitations of bent triatomic molecules, including both bending and stretching vibrations, are studied in the framework of the U(4) algebra. For the bent triatomic molecules H(2)O and H(2)S, the highly excited vibrational levels (up to 14) are obtained using the U(4) algebraic approach. We have found that the spectra are made up of clustering structure. The number of levels in one cluster depends on the total quanta of stretching and bending. In addition, some other properties are also discussed. Copyright 2000 Academic Press.     

Uniform Supersonic Expansion for FTIR Absorption Spectroscopy: The nu(5) Band of (NO)(2) at 26 K

A high-resolution Fourier transform interferometer (Bruker IFS 120 HR) was combined with a uniform supersonic expansion produced by means of axisymmetric Laval nozzles. The geometry profile of the nozzle enabled us to work under precise thermodynamic and kinetic conditions. The effect of the cooling rate of different nozzles on cluster nucleation is illustrated. The experimental sensitivity was tested by recording the nu(5) band of (NO)(2) at 26 K. Copyright 2000 Academic Press.     

The nu(12) Band of CH(3)SiD(3)

The lowest frequency degenerate fundamental band of CH(3)SiD(3) (v(12) = 1 <-- 0) centered around 418 cm(-1) was measured in order to investigate the vibration-torsion-rotation interactions in a symmetric-top molecule with a single torsional degree of freedom. The spectrum was recorded at an instrumental resolution of 0.004 cm(-1) using a Bomem Fourier transform spectrometer. The temperature and pressure of the sample were 180 K and 2 Torr, respectively. Because of the Coriolis coupling between the torsional stack with one quantum of the silyl rock excited and the corresponding stack for the ground vibrational state, torsional splittings are measured that are substantially larger than expected simply from the observed increase in the barrier height. Due to the local nature of the Coriolis perturbation, the significantly enhanced torsional splittings are confined to a few (K, varsigma) rotational series; here varsigma = -1, 0, 1 labels the torsional sublevels. The current measurements of the nu(12) band and frequencies from previously reported studies in the ground vibrational state were fitted to within experimental uncertainty using an effective Hamiltonian which was used for the analyses of similar spectra in CH(3)SiD(3) and CH(3)CD(3). Spectroscopic parameters characterizing the states v(12) = 0 and 1 and their interactions were determined, including several Coriolis-coupling constants. 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.     

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.     

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.     

High-Resolution Infrared, Microwave, and Submillimeter-Wave Study of FClO(2) in the nu(2), nu(3), nu(4), and nu(6) Excited States

A high-resolution analysis of the {nu(2), nu(3)} and {nu(4), nu(6)} bands of the two isotopomers of chloryl fluoride F(35)ClO(2) and F(37)ClO(2) has been carried out for the first time using simultaneously infrared spectra recorded around 16&mgr;m and 26&mgr;m with a resolution of ca. 0.003 cm(-1) and microwave and submillimeter-wave transitions occurring within the vibrational states 2(1), 3(1), 4(1), and 6(1). Taking into account the Coriolis resonances which link the rotational levels of the {2(1), 3(1)} and the {4(1), 6(1)} interacting states, it was possible to reproduce very satisfactorily the observed transitions and to determine accurate vibrational energies and rotational constants for the upper states 2(1), 3(1), 4(1), and 6(1) of both the (35)Cl and (37)Cl isotopic species. Copyright 2001 Academic Press.     

H(2)-Broadening Coefficients in the nu(4) Band of NH(3)

H(2)-broadening coefficients have been measured for 66 rovibrational lines of NH(3) at room temperature in the (P)P and (R)P branches of the nu(4) band in the range 1470-1600 cm(-1), using a high-resolution Fourier transform spectrometer. The collisional widths are obtained by fitting Voigt profiles to the measured shapes of the lines. The broadening coefficients are found to decrease on the whole as J increases and they increase with K for a given J value. The results are compared with those calculated from a semiclassical model in which the inversion vibration of NH(3) and collision-induced transitions with DeltaK = 0 and DeltaK = +/- 3 are taken into account. The intermolecular potential used includes electrostatic, induction, and dispersion energy contributions. The calculations performed by considering only DeltaK = 0 transitions provide significantly lower broadenings but with a satisfactory J and K dependence. The same trends are obtained for the broadening coefficients in inversion-rotation transitions and in the Q branch of the nu(1) parallel band of NH(3). Copyright 2001 Academic Press.     

High-Resolution Infrared Spectra in the C-H Region of CH2F2: The nu6 and 2nu2 Bands

High-resolution, infrared absorption spectra of the nu6 (asymmetric C-H stretch) and 2nu2 (H-C-H symmetric bend overtone) bands of jet-cooled CH2F2 are reported with a sub-Doppler resolution of approximately 0.002 cm-1. More than 600 transitions were observed in the range of 3002-3036 cm-1, of which 268 were assigned the nu6 fundamental and 184 were assigned to the 2nu2 overtone. A fit of the nu6 band to the A-reduced Watson Hamiltonian yielded eight effective constants including nu0 = 3014.0503(1), A' = 1.62868(4), B' = 0.354165(5), and C' = 0.308852(3) cm-1. Similarly, the weaker 2nu2 band was fit to seven parameters including nu0 = 3026.2297(2), and A' = 1.63396(6), B' = 0.35367(1), and C' = 0.31183(1) cm-1. Numbers in parentheses are two standard deviations in units of the last digit. Anomalous values of the A rotational constant and the DeltaK centrifugal distortion constant are attributed to an a-axis Coriolis interaction between the 2nu2 and nu6 bands. The relative intensity of the 2nu2 band is used to estimate the stretch-bend anharmonic interaction with nu1. Copyright 1999 Academic Press.     

Analysis of High-Resolution FTIR Spectrum of the nu6 Band of H13COOH

The FTIR spectrum of the nu6 band of H13COOH has been collected at a resolution of 0.004 cm-1 in the frequency range of 1030-1160 cm-1. The nu6 band was analyzed to be an A-B hybrid band and perturbed by the nearby nu8 band through a-, and b-Coriolis coupling terms. Using a Watson's A-reduced Hamiltonian in the Ir representation, with the inclusion of a- and b-Coriolis resonances, a total of 3004 IR transitions of nu6 have been analyzed to provide rovibrational constants for the v6 = 1 state with a standard deviation of 0.00047 cm-1. The nu6 band was found to be centered at 1095.40365 +/- 0.00003 cm-1. Copyright 1999 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.