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 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 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 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.     

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.     

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.     

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.     

Absolute Intensities of the nu(1) and nu(3) Bands of (16)O(3)

New experimental data on the nu(1) and nu(3) bands of (16)O(3) improving the value of absolute line intensities have been obtained. The intensities of 295 lines have been measured with an average accuracy between 2.5% and 3% and the rotational expansion of the transition moment operators for the nu(1) and nu(3) bands has been deduced. Finally, a complete listing of line intensities has been computed with an intensity cutoff of 1x10(-25) cm(-1)/molecule cm(-2). Copyright 2001 Academic Press.     

Analysis of the Coriolis Interaction between nu(6) and nu(8) Bands of HCOOH

The Fourier transform infrared (FTIR) spectrum of the nu(6) band of formic acid (HCOOH) has been recorded with a resolution of 0.0024 cm(-1) in the spectral range 1050-1160 cm(-1). The nu(6) band was found to be strongly perturbed by the nearby nu(8) band centered at about 1033.5 cm(-1). Using a Watson's A-reduced Hamiltonian in the I(r) representation, and with the inclusion of a-type Coriolis coupling constant, a simultaneous fit of nu(6) and nu(8) was performed. A total of 2485 infrared transitions including about 700 perturbed transitions of nu(6) and 19 transitions of nu(8) was fitted with an rms uncertainty of 0.0006 cm(-1). Accurate rovibrational constants up to sextic order for both nu(6) and nu(8) were obtained. The nu(6) band was analyzed to be a type AB hybrid with a band center at 1104.852109 +/- 0.000050 cm(-1). The band center for nu(8) was found to be 1033.4647 +/- 0.0021 cm(-1). 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.     

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.     

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.     

Simultaneous Analysis of the nu(2) Raman and nu(2) + nu(6) Infrared Spectra of the SF(6) Molecule

High-resolution Raman spectra of the nu(2) band of SF(6) have been recorded at a temperature of 195 K (dry ice) and a pressure of 39 mbar. These spectra were analyzed using a new set of programs specially written for XY(6) molecules. These programs, called HTDS (highly spherical top data system) in reference to the set of programs called STDS (spherical top data system written for XY(4) molecules) can be freely accessible through ftp (user anonymous) at jupiter.u-bourgogne.fr or on the web at the URL http://www.u-bourgogne.fr/LPUB/shTDS.html. The study of nu(2) was made using a Hamiltonian developed through the third order. Four parameters were determined. The standard deviation obtained using about 559 data up to J < 61 is 0.0021 cm(-1). This result is used to refine by simultaneous analysis the nu(2) and nu(2) + nu(6) bands of SF(6). This new fit allows the determination for the first time of some nu(6) parameters. The values obtained for this band (forbidden in Raman and in infrared) will be used to study the infrared hot bands in the nu(3) and nu(4) regions. Copyright 2000 Academic Press.     

The Coriolis Interaction between the nu(9) and nu(7) Fundamental Bands of Methylene Fluoride

The infrared spectrum of the nu(12) fundamental band of ethylene (C(2)H(4)) has been measured with an unapodized resolution of 0.004 cm(-1) in the frequency range of 1380-1500 cm(-1) using the Fourier transform technique. By assigning and fitting a total of 1387 infrared transitions using a Watson's A-reduced Hamiltonian in the I(r) representation, rovibrational constants for the upper state (v(12) = 1) up to five quartic and three sextic centrifugal distortions terms were derived. They represent the most accurate constants for the band so far. The rms deviation of the fit was 0.00033 cm(-1). The A-type nu(12) band with a band center at 1442.44299 +/- 0.00003 cm(-1) was found to be relatively free from local frequency perturbations. The inertial defect Delta(12) was found to be 0.24201 +/- 0.00002 u ?(2). 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.     

High-Resolution Spectroscopy and Analysis of the nu(4) Bending Region of SF(6) near 615 cm(-1)

The high-resolution Fourier transform spectrum of the nu(4) bending region of SF(6) near 615 cm(-1) has been recorded at 213 K. We were able to perform a simultaneous analysis of the nu(4) and nu(4) + nu(6) - nu(6) bands of the main isotopomer, namely (32)SF(6). This is the first detailed analysis of a hot band for this molecule. The nu(4) band of (34)SF(6) was also analyzed and the Q branch of the nu(4) band of (33)SF(6) was identified. In both cases we used the HTDS software developed in Dijon. Copyright 2001 Academic Press.     

Diode-Laser Spectroscopy of the nu(19a) Band of Chlorobenzene in a Supersonic Jet

The diode-laser absorption spectrum of the nu(19a) band of the chlorobenzene molecule cooled in a supersonic jet is presented and transitions from low J, K(a), and K(c) values (0-14) are reported. The C(6)H(5)(35)Cl band center has been found at nu(0) = 1483.894 cm(-1) and rotational constants for the upper state have been determined from a least-squares fitting to experimental data. The band center for the C(6)H(5)(37)Cl isotope has also been obtained. 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.     

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.     

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.