Microwave spectra of the ground vibrational state of formaldehyde substituted with O and O

Pure rotational transitions in the ground vibrational state have been measured for H₂¹²C¹⁸O, H₂¹²C¹⁷O, H₂¹³C¹⁸O, and H₂¹³C¹⁷O in the frequency region 8–75 GHz. These have included both Q- and R-branch transitions, and have permitted accurate evaluation of rotational constants and several quartic centrifugal distortion constants for each species. These in turn have permitted the prediction of several transitions of possible use in radioastronomy.     

A precise study of the rotational spectrum of formaldehyde H212C17O and H213C17O

The pure rotational spectra of H₂¹²C¹⁷O and H₂¹³C¹⁷O have been investigated in the frequency region between 8 and 360 GHz in the ground vibrational state. For both isotopic species the ¹⁷O nuclear quadrupole coupling constants and spin-rotation constants have been obtained. From both Q- and R-branch transitions a set of rotational constants and several distortion constants could be derived employing Watson's formalism in A reduction. The obtained rotational constants are in Megahertz:

     

3.

A precise study of the rotational spectrum of formaldehyde H₂CO, H₂CO, H₂CO, H₂CO     

R. Cornet  G. Winnewisser   《Journal of Molecular Spectroscopy》1980,80(2)

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

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4.

Infrared spectrum of CO₂ in the region of the bending fundamental ν₂     

Risto Paso  Jyrki Kauppinen  Rauno Anttila 《Journal of Molecular Spectroscopy》1980,79(1):236-253

The infrared spectrum of CO₂ in the region 540–830 cm^?1 has been studied with a Fourier spectrometer at a resolution of 0.010 cm^?1. In addition to the fundamental ν₂, more than 10 “hot” band transitions of ¹²C¹⁶O₂ have been identified. The rotational constants involved have been derived. Special care has been taken in obtaining accurate constants for the level 01¹0. The ν₂ fundamentals of the isotopic molecules ¹³C¹⁶O₂, ¹⁶O¹²C¹⁸O, and ¹⁶O¹²C¹⁷O have also been observed in a natural sample.     

5.

Centrifugal distortion analysis of pure rotational spectra of H₂¹⁶O,H₂¹⁷O,and H₂¹⁸O     

E. Kyrö 《Journal of Molecular Spectroscopy》1981,88(1):167-174

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

6.

Interpretation of the ¹³C¹⁶O₂ spectrum at 4.4 μm     

Agostino Baldacci  Louise Linden  V. Malathy Devi  K. Narahari Rao  B. Fridovich 《Journal of Molecular Spectroscopy》1978,72(1):135-142

The overlapping structure observed in the region of the ν₃ fundamental of ¹³C¹⁶O₂ at 4.4 μm has been assigned to several transitions belonging to not only the 13-C variety of carbon dioxide (¹³C¹⁶O₂) but also to ¹³C¹⁶O¹⁷O and ¹³C¹⁶O¹⁸O species occurring in the sample. Molecular constants have been evaluated for the assigned transitions.     

7.

A precise study of the rotational spectrum of formaldehyde H₂¹²C¹⁶O,H₂¹³C¹⁶O,H₂¹²C¹⁸O,H₂¹³C¹⁸O     

R. Cornet  G. Winnewisser 《Journal of Molecular Spectroscopy》1980,80(2):438-452

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

	H212C17O	H213C17O
$\text{A}$	281 965.0 (30)	281 987.3 (19)
$\text{B}$	37 812.287(45)	36 776.790(25)
$\text{C}$	33 214.523(31)	32 412.920(19)

     

8.

The rotational spectrum of water between 650 and 50 cm−1: H218O and H217O in natural abundance     

F. Winther 《Journal of Molecular Spectroscopy》1977,65(3):405-419

In the far infrared spectrum of water, 121 H₂¹⁸O and 48 H₂¹⁷O pure rotational lines have been identified. From the line frequencies and a minimum number of literature values of near infrared rotation-vibration transitions and lines from microwave spectra, the ground-state energy levels have been calculated up to J = 12 and 11, respectively. For low J levels, the agreement with earlier calculations from other microwave lines and near infrared results is within the experimental error, but deviations up to 0.6 cm^?1 are found for high J, high K_a levels.     

9.

Analysis of the Fourier transform spectra of 12C17O2 and 12C17O18O: The ν2 (15 μm) region     

M.J. Reisfeld  H. Flicker  M. Goldblatt 《Journal of Molecular Spectroscopy》1980,82(2):411-417

The vibration-rotation spectra of the ν₂ fundamental of ¹²C¹⁷O₂ and ¹²C¹⁷O¹⁸O have been obtained by Fourier transform spectroscopy at 0.05 cm^?1 resolution. The data were fitted by a least-squares routine to obtain a number of the molecular constants. The band center for ¹²C¹⁷O₂ lies at 662.0716 cm^?1 while that for ¹²C¹⁷O¹⁸O is at 659.7057 cm^?1. The difference bands ν₁ - ν₂ have also been observed for the two molecular species.     

10.

Global Multi-isotopologue fit of measured rotation and vibration–rotation line positions of CO in X1Σ+ state and new set of mass-independent Dunham coefficients     

T.I. Velichko  S.N. Mikhailenko  S.A. Tashkun 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(13):1643-1655

A set of mass-independent U_mj and Δ_mj parameters globally describing vibration–rotation energy levels of the CO molecule in the X¹Σ⁺ ground electronic state was fitted to more than 19,000 transitions of ¹²C¹⁶O, ¹³C¹⁶O, ¹⁴C¹⁶O, ¹²C¹⁷O, ¹³C¹⁷O, ¹²C¹⁸O, and ¹³C¹⁸O isotopologues collected from the literature. The maximal values of the vibrational V and the rotational J quantum numbers included in the fit was 41 and 128, respectively. The weighted standard deviation of the fit is .66. Fitted parameters were used for calculation of Dunham coefficients Y_mj for nine isotopologues ¹²C¹⁶O, ¹³C¹⁶O, ¹⁴C¹⁶O, ¹²C¹⁷O, ¹³C¹⁷O, ¹⁴C¹⁷O, ¹²C¹⁸O, ¹³C¹⁸O, and ¹⁴C¹⁸O. Calculated transition frequencies based on the fitted parameters were compared with previously reported. A critical analysis of the CO HITRAN and HITEMP data is also presented.     

11.

Infrared spectrum of isotopic carbon dioxide in the region of bending fundamental ν₂     

K. Jolma 《Journal of Molecular Spectroscopy》1985,111(2):211-218

Infrared absorption spectra of ¹³C¹⁶O₂, ¹³C¹⁸O₂, ¹⁶O¹³C¹⁷O, ¹⁶O¹³C¹⁸O, and ¹⁶O¹²C¹⁸O have been measured in the wavenumber region 570–780 cm^?1 with a spectral resolution of about 0.005 cm^?1. The data were recorded at room temperature with a Fourier transform spectrometer using a ¹³C-enriched sample of carbon dioxide. The fundamentals ν₂ and several “hot” bands have been identified and effective molecular constants have been derived.     

12.

Microwave spectrum of formic acid and its isotopic species in D, ¹³C and ¹⁸O. Study of Coriolis resonances between ν₇ and ν₉ vibrational excited states     

E. Willemot  D. Dangoisse  J. Bellet 《Journal of Molecular Spectroscopy》1978,73(1):96-119

In the investigation of the 8 → 280 GHz region, 241 and 57 transitions of H¹²COOH and DCOOH, respectively, have been assigned to the ν₇ and ν₉ vibrational states coupled by a strong Coriolis resonance. The numerical analysis based on Watson's theory of centrifugal distortion coupled with the addition of Coriolis interaction allows us to obtain a set of parameters which fits the transitions well. The rotational spectra of the isotopic species HCOOD and DCOOD have also been investigated. In this investigation 55 and 67 transitions have been assigned to the ν₇ and ν₉ vibrational states of these two molecules, respectively. A very weak Coriolis resonance was detected. Two non-rigid independent rotors were thus employed and gave us a set of parameters which fits the transitions quite well. The rotational spectrum of the ground state of H¹²COOH, H¹³COOH, HCOOD, DCOOH, H¹²C¹⁶O¹⁸OH, and H¹²C¹⁸O¹⁶OH have been reinvestigated and a set of improved parameters was obtained for each species.     

13.

The microwave spectrum of cyanophosphine, H₂PCN     

Lu Kang 《Journal of Molecular Spectroscopy》2004,225(1):66-72

The rotational spectra of cyanophosphine, H₂PCN, have been measured between 10 and 42.5 GHz by Fourier transform microwave spectroscopy. The rotational constants, centrifugal distortion constants, the ¹⁴N quadrupole coupling constant, and the nuclear spin-rotation coupling constants of ³¹P have been determined. Density functional ab initio calculations were performed, and the calculated values of the molecular constants are in excellent agreement with our experimentally determined results. The spectra of three isotopomers were measured, H₂P¹²C¹⁴N, H₂P¹³C¹⁴N, and H₂P¹²C¹⁵N. The derived r₀ structure is quite comparable to the ab initio predicted H₂PCN equilibrium geometry.     

14.

Line positions and strengths of OCO, OCO and OCO between 2200 and 7000 cm     

R.A. Toth  C.E. Miller  V. Malathy Devi 《Journal of Molecular Spectroscopy》2007,243(1):43-61

Line positions and strengths of ¹⁶O¹²C¹⁸O (628), ¹⁸O¹²C¹⁸O (828) and ¹⁷O¹²C¹⁸O (728) were measured between 2200 and 7000 cm⁻¹ using 22 near infrared (NIR) absorption spectra recorded at 0.01-0.013 cm⁻¹ resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. These data were obtained at room temperature using absorption cells with optical path lengths ranging from 2.4 to 385 m; the cells were filled with natural and ¹⁸O-enriched samples of CO₂ at pressures ranging from 0.54 to 252 torr. The observed line positions were analyzed to obtain the upper state band centers and rotational constants for 17 bands of ¹⁶O¹²C¹⁸O, 19 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O. The majority of the ¹⁸O¹²C¹⁸O and ¹⁷O¹²C¹⁸O bands were measured for the first time. In addition, the rotational constants for the lower states 00001, 01101e and 01101f were derived for all three species using the method of combination differences in which the averaged values obtained from the line positions of two or more bands were least-squares-fitted. Rovibrational parameters were also obtained for the 02201e, 02201f, 10002 and 10001 states of ¹⁸O¹²C¹⁸O. The line position analysis revealed that transitions of the levels 38 ? J′ ? 46 of the 11111f ← 01101f band of ¹⁸O¹²C¹⁸O are perturbed. Perturbed transitions were also observed for the 12212 ← 02201 band and in the high-J transitions (J′ ? 49) of the 20012 ← 00001 band of ¹⁸O¹²C¹⁸O. Band strengths and Herman-Wallis-like F-factor coefficients were determined for 21 bands of ¹⁶O¹²C¹⁸O, 25 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O from least-squares fits to more than 3700 measured transition intensities; band strengths and line positions for 34 of these bands were obtained for the first time.     

15.

Observation and analysis of fundamental bending mode of T2O     

H.A. Fry  L.H. Jones  J.E. Barefield 《Journal of Molecular Spectroscopy》1984,103(1):41-55

The absorption spectrum of the ν₂ band of T₂O vapor has been observed at 0.04 cm^?1 resolution. A total of 549 transitions has been assigned; 474 of these have been used to evaluate the rotational constants A, B, and C as well as the fourth-order and sixth-order distortion constants and one eighth-order constant for the upper vibrational state.     

16.

Rotational spectra of mono-substituted asymmetric C₆H₆-H₂O dimers     

B. Ram Prasad  E. Arunan 《Journal of Molecular Spectroscopy》2005,232(2):308-314

This paper reports the assignment of the rotational spectra of the m = 0 and 1 states of ¹³CC₅H₆-H₂O and C₆H₅D-H₂O dimers. The m = 1 progression was not identified or assigned for both ¹³CC₅H₆-H₂O and C₆H₅D-H₂O in the earlier work, though for the symmetric isotopomers (C₆H₆-H₂O/D₂O/H₂¹⁸O), they were identified [H.S. Gutowsky, T. Emilsson, E. Arunan, J. Chem. Phys. 99 (1993) 4883]. The m = 1 transitions for ¹³CC₅H₆-H₂O and C₆H₅D-H₂O were split into two, unlike that of the parent C₆H₆-H₂O isotopomer. The splitting varied, somewhat randomly, with quantum numbers J and K. The m = 0 lines of ¹³CC₅H₆-H₂O had significant overlap with the m = 1 lines of the parent isotopomer, clouding proper assignment, and leading to an rms deviation of about 200 kHz in the earlier work. The general semi-rigid molecular Hamiltonian coupled to an internal rotor, described recently by Duan et al. [Y.B. Duan, H.M. Zhang, K. Takagi, J. Chem. Phys. 104 (1996) 3914], is used in this work to assign both m = 0 and 1 states of ¹³CC₅H₆-H₂O and C₆H₅D-H₂O dimers. Consequently, the m = 0 fits for ¹³CC₅H₆-H₂O/D₂O have an rms deviation of only 4/7 kHz, comparable to experimental uncertainties. The fits for m = 1 transitions for ¹³CC₅H₆-H₂O and C₆H₅D-H₂O dimers have an rms deviation of about 200 kHz. However, it is of the same order of magnitude as that of the m = 1 state of the parent C₆H₆-H₂O dimer. The A rotational constants determined from the m = 0 fits for both ¹³CC₅H₆-H₂O and ¹³CC₅H₆-D₂O isotopomers are identical and very close to the C rotational constant for ¹³CC₅H₆. This provides a direct experimental determination for the C rotational constant of ¹³CC₅H₆, which has a negligible dipole moment.     

17.

Dunham coefficients for seven isotopic species of CO     

G. Guelachvili  D. de Villeneuve  R. Farrenq  W. Urban  J. Verges 《Journal of Molecular Spectroscopy》1983,98(1):64-79

An extensive work on vibration-rotation spectra in the fundamental ¹Σ⁺ electronic state of CO is reported. More than 30 000 Doppler-limited measurements corresponding to about 8500 transitions of 255 bands of ¹²C¹⁶O, ¹²C¹⁸O, ¹³C¹⁶O, and ¹³C¹⁸O, most of them observed for the first time, have been obtained with a high information Fourier transform interferometer on the sequences Δv = 1, 2, and 3. The highest v and J values are 41 and 93, respectively. Experimental vibrational levels are then well observed up to three fourths of the dissociation energy limit. These accurate infrared wavenumbers, with an additional selected set of all previous measurements, have been simultaneously fitted to the Dunham expression in a weighted nonlinear least-squares calculation covering seven different isotopic species. It significantly improves both the number of parameters (U and Δ) obtained by the best previous work (35 instead of 23) and their corresponding standard deviations. The rms of the fit is equal to 13 × 10^?6 cm^?1 (390 KHz). Calculated wavenumbers from the 35 reduced Dunham and mass-scaling coefficients can then be used as secondary standards, even for transitions involving high v and J values of the various isotopic species. These new parameters should be a convenient and useful tool for several purposes, such as assignment of infrared laser lines and identification of microwave and infrared transitions in astronomical spectra. The Dunham coefficients Y are also reported for ¹²C¹⁶O, ¹²C¹⁷O, ¹²C¹⁸O, ¹³C¹⁶O, ¹³C¹⁷O, ¹³C¹⁸O, and ¹⁴C¹⁶O. These experimentally determined accurate Y should also be useful for further examination of the potential energy and dipole moment formulations.     

18.

High-precision frequency measurements of the ν₁ + ν₃ combination band of C₂H₂ in the 1.5 μm region     

C.S. Edwards  G.P. Barwood  P. Gill  W.R.C. Rowley 《Journal of Molecular Spectroscopy》2005,234(1):143-148

A pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to transitions of ¹²C₂H₂ and ¹³C₂H₂, using cavity-enhanced Doppler-free saturation absorption spectroscopy. The absolute frequencies of 41 lines of the ν₁ + ν₃ band of ¹²C₂H₂, covering the spectral region 1520-1545 nm, have been measured by use of a passive optical frequency comb generator, referenced to ¹³C₂H₂ transitions of known frequency. The mean experimental uncertainties (coverage factor k = 1) of the frequency values are 3.0 kHz (type A) and 10 kHz (type B). Improved values of the band origin ν₀, rotational constants B′ and B″, and centrifugal distortion coefficients D′, D″, H′, and H″ are presented.     

19.

Infrared emission of 12C16O, 13C16O,and 12C18O     

T.R. Todd  C.M. Clayton  W.B. Telfair  T.K. McCubbin  J. Plíva 《Journal of Molecular Spectroscopy》1976,62(2):201-227

The combination of a new high-resolution grating spectrometer and a spontaneous emission source has made it possible to measure precisely the 1 → 0, 2 → 1, and 2 → 0 transitions of ¹²C¹⁶O relative to the accurately known ¹²C¹⁶O laser lines which have been referred to pure frequency standards by Eng et al. The 1 → 0 and 2 → 0 band centers agree to within 0.0002 cm^?1 with those measured relative to wavelength standards by Fourier transform spectroscopy (FTS). From a weighted simultaneous fit to the FTS-absorption, FTS-flame, our grating-emission, and microwave results, a set of calculated line positions was obtained for the 1 → 0, 2 → 1, and 2 → 0 transitions of ¹²C¹⁶O. The absolute accuracy of these line positions is believed to be ±0.0005 cm^?1 and we propose that the lines can be used as secondary wavenumber standards in the infrared.The spontaneous emission sequences v′ → (v′ ? 1) were measured for ¹²C¹⁶O up to v′ = 20, for ¹³C¹⁶O up to v′ = 11 (using a ¹³C-enriched sample), and for ¹²C¹⁸O up to v′ = 4 (in natural abundance). Internally consistent sets of Dunham coefficients were calculated from the best available data for the molecules of ¹²C¹⁶O, ¹³C¹⁶O, and ¹²C¹⁸O.     

20.

Stark spectroscopy with the CO laser: The ν3 fundamental band of H2CO     

M. Allegrini  J.W.C. Johns  A.R.W. McKellar 《Journal of Molecular Spectroscopy》1977,66(1):69-78

The ν₃ fundamental band of H₂CO (CH₂ scissoring motion) has been studied by means of CO laser Stark spectroscopy and conventional infrared absorption spectroscopy. The primary aim of the work was to determine the dipole moment of H₂CO in the v₃ = 1 state, and the value determined was 2.3250 ± 0.0025 D. The spectrum was analyzed with the inclusion of the Coriolis interactions among ν₃, ν₄, and ν₆ so that “true” rotational constants were determined for ν₃; “effective” constants obtained by ignoring these interactions were also determined. The ν₃ band origin was determined to be 1500.174 ± 0.002 cm^?1. The H₂CO spectrum was also used as a means of determining the frequencies of some ¹³C¹⁶O and ¹²C¹⁸O laser lines in the 1500 cm^?1 region relative to ¹²C¹⁶O lines.     

	H212C16O	H213C16O	H212C18O	H213C18O
A/MHz	281 970.572 (24)	281 993.258(135)	281 961.94 (39)	281 985.00 (93)
B/MHz	38 836.0456(13)	37 811.0887(25)	36 904.1693(66)	35 859.256(10)
C/MHz	34 002.2034(12)	33 213.9790(25)	32 511.5311(63)	31 697.868(10)

A precise study of the rotational spectrum of formaldehyde H2CO, H2CO, H2CO, H2CO

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

Full-size image

     

Infrared spectrum of CO2 in the region of the bending fundamental ν2

The infrared spectrum of CO₂ in the region 540–830 cm^?1 has been studied with a Fourier spectrometer at a resolution of 0.010 cm^?1. In addition to the fundamental ν₂, more than 10 “hot” band transitions of ¹²C¹⁶O₂ have been identified. The rotational constants involved have been derived. Special care has been taken in obtaining accurate constants for the level 01¹0. The ν₂ fundamentals of the isotopic molecules ¹³C¹⁶O₂, ¹⁶O¹²C¹⁸O, and ¹⁶O¹²C¹⁷O have also been observed in a natural sample.     

Centrifugal distortion analysis of pure rotational spectra of H216O,H217O,and H218O

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

Interpretation of the 13C16O2 spectrum at 4.4 μm

The overlapping structure observed in the region of the ν₃ fundamental of ¹³C¹⁶O₂ at 4.4 μm has been assigned to several transitions belonging to not only the 13-C variety of carbon dioxide (¹³C¹⁶O₂) but also to ¹³C¹⁶O¹⁷O and ¹³C¹⁶O¹⁸O species occurring in the sample. Molecular constants have been evaluated for the assigned transitions.     

A precise study of the rotational spectrum of formaldehyde H212C16O,H213C16O,H212C18O,H213C18O

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

The rotational spectrum of water between 650 and 50 cm−1: H218O and H217O in natural abundance

In the far infrared spectrum of water, 121 H₂¹⁸O and 48 H₂¹⁷O pure rotational lines have been identified. From the line frequencies and a minimum number of literature values of near infrared rotation-vibration transitions and lines from microwave spectra, the ground-state energy levels have been calculated up to J = 12 and 11, respectively. For low J levels, the agreement with earlier calculations from other microwave lines and near infrared results is within the experimental error, but deviations up to 0.6 cm^?1 are found for high J, high K_a levels.     

Analysis of the Fourier transform spectra of 12C17O2 and 12C17O18O: The ν2 (15 μm) region

The vibration-rotation spectra of the ν₂ fundamental of ¹²C¹⁷O₂ and ¹²C¹⁷O¹⁸O have been obtained by Fourier transform spectroscopy at 0.05 cm^?1 resolution. The data were fitted by a least-squares routine to obtain a number of the molecular constants. The band center for ¹²C¹⁷O₂ lies at 662.0716 cm^?1 while that for ¹²C¹⁷O¹⁸O is at 659.7057 cm^?1. The difference bands ν₁ - ν₂ have also been observed for the two molecular species.     

Global Multi-isotopologue fit of measured rotation and vibration–rotation line positions of CO in X1Σ+ state and new set of mass-independent Dunham coefficients

A set of mass-independent U_mj and Δ_mj parameters globally describing vibration–rotation energy levels of the CO molecule in the X¹Σ⁺ ground electronic state was fitted to more than 19,000 transitions of ¹²C¹⁶O, ¹³C¹⁶O, ¹⁴C¹⁶O, ¹²C¹⁷O, ¹³C¹⁷O, ¹²C¹⁸O, and ¹³C¹⁸O isotopologues collected from the literature. The maximal values of the vibrational V and the rotational J quantum numbers included in the fit was 41 and 128, respectively. The weighted standard deviation of the fit is .66. Fitted parameters were used for calculation of Dunham coefficients Y_mj for nine isotopologues ¹²C¹⁶O, ¹³C¹⁶O, ¹⁴C¹⁶O, ¹²C¹⁷O, ¹³C¹⁷O, ¹⁴C¹⁷O, ¹²C¹⁸O, ¹³C¹⁸O, and ¹⁴C¹⁸O. Calculated transition frequencies based on the fitted parameters were compared with previously reported. A critical analysis of the CO HITRAN and HITEMP data is also presented.     

Infrared spectrum of isotopic carbon dioxide in the region of bending fundamental ν2

Infrared absorption spectra of ¹³C¹⁶O₂, ¹³C¹⁸O₂, ¹⁶O¹³C¹⁷O, ¹⁶O¹³C¹⁸O, and ¹⁶O¹²C¹⁸O have been measured in the wavenumber region 570–780 cm^?1 with a spectral resolution of about 0.005 cm^?1. The data were recorded at room temperature with a Fourier transform spectrometer using a ¹³C-enriched sample of carbon dioxide. The fundamentals ν₂ and several “hot” bands have been identified and effective molecular constants have been derived.     

Microwave spectrum of formic acid and its isotopic species in D, 13C and 18O. Study of Coriolis resonances between ν7 and ν9 vibrational excited states

In the investigation of the 8 → 280 GHz region, 241 and 57 transitions of H¹²COOH and DCOOH, respectively, have been assigned to the ν₇ and ν₉ vibrational states coupled by a strong Coriolis resonance. The numerical analysis based on Watson's theory of centrifugal distortion coupled with the addition of Coriolis interaction allows us to obtain a set of parameters which fits the transitions well. The rotational spectra of the isotopic species HCOOD and DCOOD have also been investigated. In this investigation 55 and 67 transitions have been assigned to the ν₇ and ν₉ vibrational states of these two molecules, respectively. A very weak Coriolis resonance was detected. Two non-rigid independent rotors were thus employed and gave us a set of parameters which fits the transitions quite well. The rotational spectrum of the ground state of H¹²COOH, H¹³COOH, HCOOD, DCOOH, H¹²C¹⁶O¹⁸OH, and H¹²C¹⁸O¹⁶OH have been reinvestigated and a set of improved parameters was obtained for each species.     

The microwave spectrum of cyanophosphine, H2PCN

The rotational spectra of cyanophosphine, H₂PCN, have been measured between 10 and 42.5 GHz by Fourier transform microwave spectroscopy. The rotational constants, centrifugal distortion constants, the ¹⁴N quadrupole coupling constant, and the nuclear spin-rotation coupling constants of ³¹P have been determined. Density functional ab initio calculations were performed, and the calculated values of the molecular constants are in excellent agreement with our experimentally determined results. The spectra of three isotopomers were measured, H₂P¹²C¹⁴N, H₂P¹³C¹⁴N, and H₂P¹²C¹⁵N. The derived r₀ structure is quite comparable to the ab initio predicted H₂PCN equilibrium geometry.     

Line positions and strengths of OCO, OCO and OCO between 2200 and 7000 cm

Line positions and strengths of ¹⁶O¹²C¹⁸O (628), ¹⁸O¹²C¹⁸O (828) and ¹⁷O¹²C¹⁸O (728) were measured between 2200 and 7000 cm⁻¹ using 22 near infrared (NIR) absorption spectra recorded at 0.01-0.013 cm⁻¹ resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. These data were obtained at room temperature using absorption cells with optical path lengths ranging from 2.4 to 385 m; the cells were filled with natural and ¹⁸O-enriched samples of CO₂ at pressures ranging from 0.54 to 252 torr. The observed line positions were analyzed to obtain the upper state band centers and rotational constants for 17 bands of ¹⁶O¹²C¹⁸O, 19 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O. The majority of the ¹⁸O¹²C¹⁸O and ¹⁷O¹²C¹⁸O bands were measured for the first time. In addition, the rotational constants for the lower states 00001, 01101e and 01101f were derived for all three species using the method of combination differences in which the averaged values obtained from the line positions of two or more bands were least-squares-fitted. Rovibrational parameters were also obtained for the 02201e, 02201f, 10002 and 10001 states of ¹⁸O¹²C¹⁸O. The line position analysis revealed that transitions of the levels 38 ? J′ ? 46 of the 11111f ← 01101f band of ¹⁸O¹²C¹⁸O are perturbed. Perturbed transitions were also observed for the 12212 ← 02201 band and in the high-J transitions (J′ ? 49) of the 20012 ← 00001 band of ¹⁸O¹²C¹⁸O. Band strengths and Herman-Wallis-like F-factor coefficients were determined for 21 bands of ¹⁶O¹²C¹⁸O, 25 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O from least-squares fits to more than 3700 measured transition intensities; band strengths and line positions for 34 of these bands were obtained for the first time.     

Observation and analysis of fundamental bending mode of T2O

The absorption spectrum of the ν₂ band of T₂O vapor has been observed at 0.04 cm^?1 resolution. A total of 549 transitions has been assigned; 474 of these have been used to evaluate the rotational constants A, B, and C as well as the fourth-order and sixth-order distortion constants and one eighth-order constant for the upper vibrational state.     

Rotational spectra of mono-substituted asymmetric C6H6-H2O dimers

This paper reports the assignment of the rotational spectra of the m = 0 and 1 states of ¹³CC₅H₆-H₂O and C₆H₅D-H₂O dimers. The m = 1 progression was not identified or assigned for both ¹³CC₅H₆-H₂O and C₆H₅D-H₂O in the earlier work, though for the symmetric isotopomers (C₆H₆-H₂O/D₂O/H₂¹⁸O), they were identified [H.S. Gutowsky, T. Emilsson, E. Arunan, J. Chem. Phys. 99 (1993) 4883]. The m = 1 transitions for ¹³CC₅H₆-H₂O and C₆H₅D-H₂O were split into two, unlike that of the parent C₆H₆-H₂O isotopomer. The splitting varied, somewhat randomly, with quantum numbers J and K. The m = 0 lines of ¹³CC₅H₆-H₂O had significant overlap with the m = 1 lines of the parent isotopomer, clouding proper assignment, and leading to an rms deviation of about 200 kHz in the earlier work. The general semi-rigid molecular Hamiltonian coupled to an internal rotor, described recently by Duan et al. [Y.B. Duan, H.M. Zhang, K. Takagi, J. Chem. Phys. 104 (1996) 3914], is used in this work to assign both m = 0 and 1 states of ¹³CC₅H₆-H₂O and C₆H₅D-H₂O dimers. Consequently, the m = 0 fits for ¹³CC₅H₆-H₂O/D₂O have an rms deviation of only 4/7 kHz, comparable to experimental uncertainties. The fits for m = 1 transitions for ¹³CC₅H₆-H₂O and C₆H₅D-H₂O dimers have an rms deviation of about 200 kHz. However, it is of the same order of magnitude as that of the m = 1 state of the parent C₆H₆-H₂O dimer. The A rotational constants determined from the m = 0 fits for both ¹³CC₅H₆-H₂O and ¹³CC₅H₆-D₂O isotopomers are identical and very close to the C rotational constant for ¹³CC₅H₆. This provides a direct experimental determination for the C rotational constant of ¹³CC₅H₆, which has a negligible dipole moment.     

Dunham coefficients for seven isotopic species of CO

An extensive work on vibration-rotation spectra in the fundamental ¹Σ⁺ electronic state of CO is reported. More than 30 000 Doppler-limited measurements corresponding to about 8500 transitions of 255 bands of ¹²C¹⁶O, ¹²C¹⁸O, ¹³C¹⁶O, and ¹³C¹⁸O, most of them observed for the first time, have been obtained with a high information Fourier transform interferometer on the sequences Δv = 1, 2, and 3. The highest v and J values are 41 and 93, respectively. Experimental vibrational levels are then well observed up to three fourths of the dissociation energy limit. These accurate infrared wavenumbers, with an additional selected set of all previous measurements, have been simultaneously fitted to the Dunham expression in a weighted nonlinear least-squares calculation covering seven different isotopic species. It significantly improves both the number of parameters (U and Δ) obtained by the best previous work (35 instead of 23) and their corresponding standard deviations. The rms of the fit is equal to 13 × 10^?6 cm^?1 (390 KHz). Calculated wavenumbers from the 35 reduced Dunham and mass-scaling coefficients can then be used as secondary standards, even for transitions involving high v and J values of the various isotopic species. These new parameters should be a convenient and useful tool for several purposes, such as assignment of infrared laser lines and identification of microwave and infrared transitions in astronomical spectra. The Dunham coefficients Y are also reported for ¹²C¹⁶O, ¹²C¹⁷O, ¹²C¹⁸O, ¹³C¹⁶O, ¹³C¹⁷O, ¹³C¹⁸O, and ¹⁴C¹⁶O. These experimentally determined accurate Y should also be useful for further examination of the potential energy and dipole moment formulations.     

High-precision frequency measurements of the ν1 + ν3 combination band of C2H2 in the 1.5 μm region

A pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to transitions of ¹²C₂H₂ and ¹³C₂H₂, using cavity-enhanced Doppler-free saturation absorption spectroscopy. The absolute frequencies of 41 lines of the ν₁ + ν₃ band of ¹²C₂H₂, covering the spectral region 1520-1545 nm, have been measured by use of a passive optical frequency comb generator, referenced to ¹³C₂H₂ transitions of known frequency. The mean experimental uncertainties (coverage factor k = 1) of the frequency values are 3.0 kHz (type A) and 10 kHz (type B). Improved values of the band origin ν₀, rotational constants B′ and B″, and centrifugal distortion coefficients D′, D″, H′, and H″ are presented.     

Infrared emission of 12C16O, 13C16O,and 12C18O

The combination of a new high-resolution grating spectrometer and a spontaneous emission source has made it possible to measure precisely the 1 → 0, 2 → 1, and 2 → 0 transitions of ¹²C¹⁶O relative to the accurately known ¹²C¹⁶O laser lines which have been referred to pure frequency standards by Eng et al. The 1 → 0 and 2 → 0 band centers agree to within 0.0002 cm^?1 with those measured relative to wavelength standards by Fourier transform spectroscopy (FTS). From a weighted simultaneous fit to the FTS-absorption, FTS-flame, our grating-emission, and microwave results, a set of calculated line positions was obtained for the 1 → 0, 2 → 1, and 2 → 0 transitions of ¹²C¹⁶O. The absolute accuracy of these line positions is believed to be ±0.0005 cm^?1 and we propose that the lines can be used as secondary wavenumber standards in the infrared.The spontaneous emission sequences v′ → (v′ ? 1) were measured for ¹²C¹⁶O up to v′ = 20, for ¹³C¹⁶O up to v′ = 11 (using a ¹³C-enriched sample), and for ¹²C¹⁸O up to v′ = 4 (in natural abundance). Internally consistent sets of Dunham coefficients were calculated from the best available data for the molecules of ¹²C¹⁶O, ¹³C¹⁶O, and ¹²C¹⁸O.     

Stark spectroscopy with the CO laser: The ν3 fundamental band of H2CO

The ν₃ fundamental band of H₂CO (CH₂ scissoring motion) has been studied by means of CO laser Stark spectroscopy and conventional infrared absorption spectroscopy. The primary aim of the work was to determine the dipole moment of H₂CO in the v₃ = 1 state, and the value determined was 2.3250 ± 0.0025 D. The spectrum was analyzed with the inclusion of the Coriolis interactions among ν₃, ν₄, and ν₆ so that “true” rotational constants were determined for ν₃; “effective” constants obtained by ignoring these interactions were also determined. The ν₃ band origin was determined to be 1500.174 ± 0.002 cm^?1. The H₂CO spectrum was also used as a means of determining the frequencies of some ¹³C¹⁶O and ¹²C¹⁸O laser lines in the 1500 cm^?1 region relative to ¹²C¹⁶O lines.