Variational Calculations of Rovibrational Energies for CO(2)

In this work, the BaI D(2)Sigma(+) and G(2)Sigma(+) electronic states were investigated using laser-induced fluorescence (LIF) and Fourier transform spectroscopy (FTS). The LIF visible spectra were obtained by using the second harmonic of the Ti:sapphire single-mode laser and the Ar(+) and Kr(+) multimode lasers as excitation sources. Previously recorded data, taken from C. A. Leach, A. A. Tsekouras, and R. N. Zare (1992, J. Mol. Spectrosc. 153, 59-72) and from R. F. Gutterres, J. Vergès, and C. Amiot (1999, J. Mol. Spectrosc. 196, 29-44; 2000, J. Mol. Spectrosc. 200, 253-260; and 2000, J. Mol. Spectrosc. 201, 326-327) were combined with the present data. Accurate and improved molecular constants for the X(2)Sigma(+), B(2)Sigma(+), A('2)Delta, A(2)Pi, C(2)Pi, and D(2)Sigma(+) states and 16 term values of the G(2)Sigma(+) state were derived from a simultaneous treatment of the whole data set (12 684 transitions) with a standard deviation of 3.26x10(-3) cm(-1). Copyright 2001 Academic Press.     

Analysis of the 1-v" Progression of the 3A Band System (c(3)Pi-a(3)Pi) in the (13)C(16)O Molecule Spectrum

The 1-0, 1-1, and 1-2 bands of the 3A system of (13)CO (c(3)Pi-a(3)Pi) have been recorded for the first time, in the form of discharge emission spectra photographed at high resolution. Preliminary rotational analysis suggests that the v = 1 level of the c(3)Pi state is perturbed in a fashion similar to the v = 0 level, previously observed by Dabrowski et al. (1987. I. Dabrowski, M. Vervolet, and D. C. Wang, Can. J. Phys. 65, 1171-1177). Rotational combination differences from the 1720 measured lines have been used to obtain rotational constants for the v = 0-2 levels of the a(3)Pi state, using the Hamiltonian of Brown et al. (1979. J. M. Brown, E. A. Calbourn, J. K. G. Watson, and F. D. Wayne, J. Mol. Spectrosc. 74, 294-318). and the least squares formalism of Curl and Dane (1988. J. Mol. Spectrosc. 128, 406-412), as modified by Watson (1989. J. Mol. Spectrosc. 138, 302-308). Term values for the c(3)Pi, v = 1 level have then been obtained from the line frequencies, and a set of effective rotational constants for the c(3)Pi (v = 1) level of (13)CO has been derived. Copyright 2000 Academic Press.     

Submillimeter-wave spectrum of the FCO radical

The submillimeter-wave spectrum of FCO has been measured using a backward-wave oscillator based spectrometer in conjunction with a free space absorption cell. The FCO radical has been produced in glow discharge plasma of a gaseous mixture of F₂CO, Ar, and He. A total of 109 a-type, R-branch lines have been measured in the 355-638 GHz region and have been analyzed together with the low-J transitions observed by means of Fourier Transform microwave spectroscopy [H. Habara, S. Yamamoto, J. Mol. Spectrosc. 207 (2001) 238]. Twenty-one molecular constants have been determined accurately including the fine and hyperfine interaction constants. Comparison of the hyperfine constants with ab initio values and matrix electron spin resonance data has been made.     

Anomalous Vibrational Dependence of the Rotational and Hyperfine Parameters in the B(4)Pi-X(4)Sigma(-) Transition of NbO

The laser excitation spectrum of jet-cooled NbO in the region 16 000-18 000 cm(-1) has been recorded at high resolution, giving rotational and hyperfine constants for the levels v=0-3 of the B(4)Pi state and v=1 of the X(4)Sigma(-) state; zero gaps have also been measured at low resolution for some weaker bands involving higher vibrational levels. Taken together with the laser data for the B-X (0,0) band from Adam et al. (J. Chem. Phys. 94, 6240-6262 (1994)) and the Fourier transform emission data for the doublet manifold from Launila et al. (J. Mol. Spectrosc. 186, 131-143 (1997)), the new data give a very complete picture of the vibrational energy level pattern in this region. Strong irregularities in the vibrational dependences of the B(4)Pi rotational and hyperfine constants can be interpreted in terms of spin-orbit interaction between the B(4)Pi state and the f(2)Pi, e(2)Phi, and d(2)Delta states. The interaction is strong enough that all three doublet states can be seen in absorption from the X(4)Sigma(-) ground state, adding to the complexity of the spectrum. The hitherto unknown sigmadeltasigma* (4)Delta state is estimated to lie near 17 500 cm(-1), from the change of sign in the spin-rotation parameter gamma of the B(4)Pi state between v=2 and 3. Copyright 2001 Academic Press.     

Fourier Transform Spectroscopy of the O(2) Herzberg Bands

From absorption spectra obtained at high resolution by coupling a Fourier transform spectrometer to a long-path multiple reflection cell [A. Jenouvrier, M.-F. Mérienne, B. Coquart, M. Carleer, S. Fally, A. C. Vandaele, C. Hermans, and R. Colin, J. Mol. Spectrosc. 198, 136-162 (1999)] the intensities of the O(2) Herzberg bands (A(3)Sigma(+)(u)-X(3)Sigma(-)(g), c(1)Sigma(-)(u)-X(3)Sigma(-)(g), A'( 3)Delta(u)-X(3)Sigma(-)(g)) have been studied at ambient temperature. The integrated cross section values are given for the lines of the (v'-0) bands in the A(3)Sigma(+)(u)-X(3)Sigma(-)(g), c(1)Sigma(-)(u)-X(3)Sigma(-)(g), and A'( 3)Delta(u)-X(3)Sigma(-)(g) transitions with v' = 0-11, v' = 2-19, and v' = 2-12, respectively. The band oscillator strengths have been deduced and transition moments have been calculated. The total absorption values in the region of the Herzberg bands together with the photoabsorption values determined previously above the dissociation limit can be modeled by a single curve, in agreement with the continuity relationship of the cross sections through the dissociation limit. Copyright 2000 Academic Press.     

Dipole-Moment Derivatives of Nitrous Oxide

The equations relating the q(2)J-type parameters of the matrix elements of the effective dipole-moment operator with the force field constants and the dipole-moment derivatives have been established by means of contact transformations in the case of nitrous oxide molecule. The effective dipole-moment operator corresponds to the reduced effective Hamiltonian derived by J.-L. Teffo, V. I. Perevalov, and O. M. Lyulin (J. Mol. Spectrosc. 168, 390-403 (1994)) for the global treatment of the vibrational-rotational energy levels of this molecule. Using these equations, the first and second derivatives of the dipole-moment function of the nitrous oxide molecule have been determined from the published values (O. M. Lyulin, V. I. Perevalov, and J.-L. Teffo, J. Mol. Spectrosc. 174, 566-580 (1995)) of the matrix element parameters of the effective dipole-moment operator. Copyright 2001 Academic Press.     

Radiofrequency, Centimeter-Wave, Millimeter-Wave, and Infrared Spectra of SiHF(3): Investigation of the Ground, v(4) = 1, and v(6) = 1 Vibrational States

The present paper deals with the analysis of the microwave, millimeter-wave, and infrared spectra of (28)SiHF(3) in its ground, v(6) = 1 and v(4) = 1 excited states. The former was observed up to 1055 GHz leading to the determination of one octic centrifugal distortion constant, L(J) = -0.0749(55) μHz. Furthermore the interaction term ||h(3,GS) || = 1.1032(70) mHz has been fitted from splittings of six K = 3 lines. The excited states have been regarded as isolated ones. This enabled fits according the Q-, D-, and QD-reduction schemes proposed by E. I. Lobodenko, O. N. Sulakshina, V. I. Perevalov, and Vl. G. Tyuterev, (J. Mol. Spectrosc. 126, 159-170 (1987)) and further developed by J. K. G. Watson, C. Gerke, H. Harder, and K. Sarka, (J. Mol. Spectrosc. 187, 131-141 (1997)) and Harder (J. Mol. Spectrosc. 194, 145 (1999)). A multiple fit analysis was performed confirming the assumption that the excited states are not affected by intervibrational resonances. Finally the millimeter spectrum of (29)SiHF(3) and (30)SiHF(3) in their ground state was also measured up to 460 GHz and accurate rotational and centrifugal distortion parameters were derived. Copyright 2000 Academic Press.     

Rotational Analysis of the Ground State and the Lowest Fundamentals nu(3), nu(5), and nu(6) of (13)CH(3)D

The nu(3), nu(5), and nu(6) fundamental bands of the (13)CH(3)D molecule have been studied with Fourier transform infrared spectroscopy. The spectra and results for the parent species (12)CH(3)D (O. N. Ulenikov, G. A. Onopenko, N. E. Tyabaeva, J. Schroderus, and S. Alanko, J. Mol. Spectrosc. 193, 249-259 (1999)) have been used to assign and analyze about 1900 lines belonging to the (13)CH(3)D isotopic species. About 850 ground state combination differences with DeltaK = 0 were calculated, which allowed us to determine the J-dependent ground state rotational constants. The K-dependent constants as well as those describing the a(1)-a(2) (K = 3) splitting were fixed to the values obtained for the (12)CH(3)D species. The (v(3) = 1), (v(5) = 1), and (v(6) = 1) states were fit simultaneously by including the intervibrational interactions in the Hamiltonian. The rotational energies, the rotational and centrifugal distortion constants, as well as the resonance parameters involving the three states have been determined and discussed. Copyright 2000 Academic Press.     

Intensity Measurements and Collision-Broadening Coefficients for the Oxygen A Band Measured by Intracavity Laser Absorption Spectroscopy

High-sensitivity, high-resolution intracavity laser absorption spectroscopy (ICLAS) has been used to measure line intensities, nitrogen-broadening coefficients, and self-broadening coefficients in the A band (b(1)Sigma(+)(g) <-- X(3)Sigma(-)(g)) of oxygen. Both linear cavity and ring cavity ICLAS configurations were used for these measurements, and the results were intercompared. The results were compared to values measured using long-path multiple-reflection cells by K. D. Ritter and T. D. Wilkinson [J. Mol. Spectrosc. 121, 1-19 (1987)] and L. Brown and C. Plymate, [J. Mol. Spectrosc. 199, 166-179 (2000)]. New results are included for weakly absorbing transitions, not observed in the earlier measurements, such as high rotational states (up to J = 39), hot-band transitions (v' = 1 <-- v" = 1), and isotopically substituted species ((18)O(2) and (16)O(18)O). Isotopic variants ((16)O(2), (18)O(2), and (16)O(18)O) have similar broadening coefficients for corresponding rotational levels, but the self-broadening coefficients are larger in the hot band (v' = v" = 1) as compared with v' = v" = 0 transitions. An ECS-EP scaling analysis of the v' = v" = 0 self-broadening data accurately represents the available data, with the exception of the N = 0 and N = 1 levels. Copyright 2000 Academic Press.     

Infrared and Millimeter-Wave Study of the Four Lowest Torsional States of CH(3)CF(3)

An investigation of the torsion-rotation Hamiltonian of CH(3)CF(3) in the ground vibrational state has been carried out using infrared and mm-wave spectroscopy. With infrared Fourier transform spectroscopy, the weak, torsional overtone (v(6) = 2 <-- 0) has been studied leading to the measurement of 382 frequencies between 405 and 440 cm(-1) at a resolution of 0.005 cm(-1). Torsional splittings on the order of 0.03 cm(-1) were observed. With mm-wave methods, a total of 669 rotational transitions between 50 and 360 GHz have been measured at Doppler-limited resolution in the four lowest torsional states v(6) = 0, 1, 2, 3. The experimental uncertainty attained for an isolated line was better than 10 kHz below 150 GHz, and somewhat larger at higher frequencies. For v(6) = 3, torsional splittings as large as 8.7 MHz were observed. The global data set consisted of the current frequency determinations and the 443 measurements with molecular beam, microwave, and mm-wave methods analyzed by I. Ozier, J. Schroderus, S.-X. Wang, G. A. McRae, M. C. L. Gerry, B. Vogelsanger, and A. Bauder [J. Mol. Spectrosc. 190, 324-340 (1998)]. The observation of mm-wave R-branch transitions for v(6) = 1 led to a change in the J-assignment of the forbidden (Deltak = +/-3) transitions reported earlier for this torsional state. A good fit was obtained by varying 24 parameters in a Hamiltonian that represented both the torsional effects and the sextic splittings. In the earlier work, the large reduced barrier height led to high correlations among several of the torsional distortion constants. With the current measurements, many of these correlations are substantially reduced. Improved effective values were determined for the height V(3) of the hindering barrier and the first-order correction V(6) in the Fourier expansion of the potential function. The dipole function which characterizes the transition moment of the torsional overtone (v(6) = 2 <-- 0) can be written as the product of a single effective dipole constant μ(T)(0,eff) and the appropriate off-diagonal matrix element of (1 - cos 3alpha)/2, where alpha is the torsional angle. From an intensity analysis of the infrared spectrum, it has been determined that |μ(T)(0,eff)| = 85.3(62) mD. A novel approach based on a simple regrouping of angular momentum operators is introduced for decoupling the torsional and rotational degrees of freedom. 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.     

First Observation of the nu(17)-nu(4) Difference Bands of Diborane (10)B(2)H(6) and (11)B(2)H(6)

An analysis of the nu(17)-nu(4) difference bands near 800 cm(-1) of two isotopic species, (10)B(2)H(6) and (11)B(2)H(6), of diborane has been carried out using infrared spectra recorded with a resolution of ca. 0.003 cm(-1). In addition, the nu(17) band of (10)B(2)H(6) has been recorded and assigned. Since this band in (11)B(2)H(6) had already been studied (R. L. Sams, T. A. Blake, S. W. Sharpe, J.-M. Flaud, and W. J. Lafferty, J. Mol. Spectrosc. 191, 331-342 (1998)), it was possible to derive precise energy levels and Hamiltonian constants for the 4(1) vibrational states of both isotopic species. Copyright 2000 Academic Press.     

SO2: High-resolution analysis of the (0 3 0), (1 0 1), (1 1 1), (0 0 2) and (2 0 1) vibrational states; determination of equilibrium rotational constants for sulfur dioxide and anharmonic vibrational constants

High resolution Fourier transform spectra of a sample of sulfur dioxide, enriched in ³⁴S (95.3%). were completely analyzed leading to a large set of assigned lines. The experimental levels derived from this set of transitions were fit to within their experimental uncertainties using Watson-type Hamiltonians. Precise band centers, rotational and centrifugal distortion constants were determined. The following band centers in cm⁻¹ were obtained: ν₀(3ν₂)=1538.720198(11), ν₀(ν₁ + ν₃)=2475.828004(29), ν₀(ν₁ + ν₂ + ν₃)=2982.118600(20), ν₀(2ν₃)=2679.800919(35), and ν₀(2ν₁ + ν₃)=3598.773915(38). The rotational constants obtained in this work have been fit together with the rotational constants of lower-lying vibrational states [W.J. Lafferty, J.-M. Flaud, R.L. Sams, EL Hadjiabib, J. Mol. Spectrosc. 252 (2008) 72-76] to obtain equilibrium constants as well as vibration-rotation constants. These equilibrium constants have been fit together with those of ³²S¹⁶O₂ [J.-M. Flaud, W.J. Lafferty, J. Mol. Spectrosc. 16 (1993) 396-402] leading to an improved equilibrium structure. Finally the observed band centers have been fit to obtain anharmonic rotational constants.     

Assignments of several groups of iodine (I2) lines in the B-X system

The spectra obtained by means of Fourier spectroscopy and the assignments of the B-X lines of I₂ in the vicinity of two argon ion laser lines (5145 and 5287 Å), three krypton ion laser lines (5208, 5308, and 5683 Å), and one HeNe laser line (6119 Å) are given. A detailed comparison, in the vicinity of the argon ion laser line (5145 Å), between the iodine wavenumbers calculated by means of the two sets of molecular constants previously published [Wei and Tellinghuisen, J. Mol. Spectrosc.50, 317–332 (1974); Barrow and Yee, J. C. S. Faraday II. 69, 684–700 (1973)] with those calculated from Fourier spectroscopy data, is presented.     

Absolute frequency measurement of CO2 laser lines with a femtosecond laser comb and new determination of the CO2 molecular constants and frequency grid

Absolute frequency measurements of a CO₂ laser stabilized on saturated absorption resonances of CO₂ laser lines are reported. They were performed using a femtosecond-laser frequency comb generator and two laser diodes at 852 and 782 nm as intermediate oscillators, with their frequency difference phase-locked to the CO₂ laser. Twenty ¹²C¹⁶O₂ laser lines in the P and R bands at 9 μm were measured with a relative uncertainty of a few 10⁻¹² limited by the CO₂ frequency reproducibility. A new determination of the CO₂ molecular constants was obtained from these data and previous measurements in the 10 μm band. The CO₂ frequency grid was also calculated, with an improvement of two orders of magnitude compared to the previous grid of Maki et al. [J. Mol. Spectrosc. 167 (1994) 211].     

Water line parameters for weak lines in the range 7400-9600 cm

A long pathlength, Fourier transform spectrum of pure water vapour [J. Mol. Spectrosc. 211 (2002) 169] has been fitted and analysed. Line centres, intensities, and self-broadening parameters have been obtained for about 3900 lines with intensities less then 1 × 10⁻²⁴ cm/molecule. Transitions to 240 newly observed energy levels of H₂O have been identified. 855 lines have been assigned to three other major isotopologues of water. It is pointed out that a new intensity measurements are needed for the stronger lines in this region.     

High-Resolution Study of the nnu(2), n = 1, 2, 3, Vib-Rotational Bands of D(2)Se

High-resolution Fourier transform spectra of the D(2)(M)Se with M = 76, 77, 78, 80, and 82 in the regions of the first and second bending overtones 2nu(2) and 3nu(2) near 1480 and 2210 cm(-1), respectively, were recorded for the first time and assigned. On the basis of these experimental data, rotation-vibration energies were determined and fitted together with those of the (010) state reported earlier (W. Jerembeck, H. Bürger, J.-M. Flaud, and Ph. Arcas, J. Mol. Spectrosc. 197, 215-221 (1999)) by using the "Global Fit" procedure. The obtained set of 43 fitted parameters for these three vibrational states of the D(2)(80)Se species (altogether 86 fitted parameters for 12 states of five M species) reproduces the rotation-vibration energies of all studied states with accuracies close to experimental uncertainties. Copyright 2000 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 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.     

Fourier Transform Spectroscopy of the O(2) Herzberg Bands. III. Absorption Cross Sections of the Collision-Induced Bands and of the Herzberg Continuum

Absorption spectra of molecular oxygen were measured in the laboratory under temperature and pressure conditions prevailing in the Earth's atmosphere. Spectra of pure O(2), O(2) + N(2), and O(2) + Ar were recorded in the 41 700 to 33 000 cm(-1) region (240-300 nm) at a maximal optical path difference of 0.45 cm using a Fourier transform spectrometer and a multiple reflection gas cell. The different components of the spectra, namely the discrete bands of the three Herzberg systems, the Herzberg continuum, and the collision-induced diffuse Wulf bands, were separated. The contribution of the Herzberg bands was first subtracted using the line parameters determined previously [A. Jenouvrier, M.-F. Mérienne, B. Coquart, M. Carleer, S. Fally, A. C. Vandaele, C. Hermans, and R. Colin, J. Mol. Spectrosc. 198, 136-162 (1999)] from high-resolution data. Spectra recorded at various pressures then made it possible to determine by linear regression the intensity of the Wulf bands and the Herzberg continuum. The characteristics of the Wulf bands have been investigated in details: vibrational analysis, pressure effect, foreign gas effect, and a simulated spectrum are reported. The Herzberg continuum cross section is determined below the dissociation limit. A comparison with literature data is given. The new O(2) absorption cross sections and O(2)-O(2) collision-induced absorption cross sections are useful in connection with atmospheric measurements of ozone and other trace gases in the UV spectral region. Copyright 2000 Academic Press.