Carbon-13 Isotopic Species of H2C3, H2C4, and H2C5: High-Resolution Rotational Spectra

The microwave rotational spectra of the carbon-13 isotopic species of H₂C₃, H₂C₄, and H₂C₅ have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. At high resolution all of the rotational lines exhibit hyperfine structure produced by the magnetic interaction between the nuclear spin of ¹³C and the overall rotation of the molecule. The component of the nuclear spin-rotation tensor along the a-inertial axis is large for most isotopic species, especially at the carbene carbon; at this position C_aa is two to three times larger than at other substituted positions along the chain. In contrast to both H₂C₃ and H₂C₃, in H₂C₄C_aa exhibits a pronounced alternation along the carbon chain backbone. Following detection of the five carbon-13 isotopic species and D₂C₅, an experimental structure (r₀) has been determined to high accuracy for H₂C₅.     

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.     

The structure of H2CSe from microwave spectroscopy

The microwave spectra of six isotopic species of selenoformaldehyde, H₂¹³C^78,80Se, D₂C^78,80Se, and DHC^78,80Se have been assigned. The resultant rotational constants, together with those of previous work yield the following substitution structure: r(C=Se) = 175.31 pm, HCH = 117.93°, and r(C---H) = 109.04 pm. This structure is compared with the equilibrium structure derived from ab initio calculations. The fundamental vibrational frequencies and centrifugal distortion constants of H₂C⁸⁰Se have been calculated.     

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:

     

5.

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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6.

The interacting states (020), (100), and (001) of H₂¹⁷O and H₂¹⁸O     

C. Camy-Peyret  J.-M. Flaud  R.A. Toth 《Journal of Molecular Spectroscopy》1981,87(1):233-241

A fit of about 350 rotational levels of the (020), (100), and (001) vibrational states has been performed for H₂¹⁷O as well as for H₂¹⁸O leading to the determination of 51 rotational and coupling constants for each isotopic species. The Fermi-type interaction and the two Coriolis-type interactions have been taken into account by appropriate rotation-vibration operators and the v-diagonal part of the Hamiltonian is, for each vibrational state, a Watson-type Hamiltonian. The results are very satisfactory since 87% of the experimental levels are reproduced within 15 × 10^?3 cm^?1.     

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.

Analysis of ν₂ of H₂Se     

Wm.C. Lane  T.H. Edwards  James R. Gillis  Francis S. Bonomo  Frank J. Murcray 《Journal of Molecular Spectroscopy》1984,107(2):306-317

The infrared absorption spectrum of ν₂ of H₂Se in the region from 885 to 1347 cm^?1 was obtained with a resolution limit of 0.025 cm^?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 1604 lines for the six isotopomers of H₂Se, including 25 lines for the H₂⁷⁴Se isotopomer, and have analyzed them using Watson's A-reduced Hamiltonian in the I^r rotational representation. Ground state constants for each of the five most abundant isotopomers were obtained from fits of microwave transitions combined with weighted averaged ground state combination differences formed from the infrared bands (010), (020), (100), and (001). Upper state constants for each of the five most abundant isotopomers were obtained from least-squares fits of the spectral lines of ν₂, keeping the ground state constants fixed to the values determined from our ground state fits. An alternate set of ground state constants together with isotopic mass adjustment constants for all six isotopomers was determined by simultaneously fitting all available microwave transitions and infrared ground state combination differences. Keeping this set of ground state constants fixed, a single set of upper state constants and isotopic mass adjustment constants for the ν₂ band was determined by a simultaneous fit of infrared spectral lines from all six isotopomers.     

9.

The rotational a-type sepctra of ¹⁵N-labeled diazirine,H₂CN₂     

Jürgen Vogt  Manfred Winnewisser  Jørn Johs. Christiansen 《Journal of Molecular Spectroscopy》1984,103(1):95-104

The rotational a-type spectra of isotopically enriched diazirine isotopomers, H₂¹²C¹⁴N¹⁵N and H₂¹²C¹⁵N₂, have been recorded in the region between 8 and 300 GHZ; the latter isotopomer has been observed for the first time. Using Watson's A-reduced Hamiltonian, the rotational constants and the quartic and some sextic centrifugal distortion constants have been determined for the ground vibrational states.     

10.

Reaction products from a discharge of N₂ and H₂S: The microwave spectrum of two conformers of sulfur diimide (HNSNH)     

R.D. Suenram  F.J. Lovas  W.J. Stevens 《Journal of Molecular Spectroscopy》1985,112(2):482-493

The rotational spectra of two conformations of sulfur diimide (HNSNH) are reported. The HNSNH species are produced in a low-pressure microwave discharge of N₂ and H₂S. The microwave spectrum of the normal isotopic form, HNSNH, and dideutro form, DNSND, of the cis,trans and cis,cis forms have been observed. The electric dipole moment components of both forms have been determined. The molecular structures were determined from the experimental rotational constants and from geometry optimized ab initio calculations with 4-31G Gaussian basis sets and CEP-31G basis sets including polarization. The experimentally and theoretically derived molecular properties are found to be in good agreement.     

11.

The microwave spectrum and centrifugal distortion constants of difluoroborane,HBF₂     

N.P.C. Westwood  W. Lewis-Bevan  M.C.L. Gerry 《Journal of Molecular Spectroscopy》1984,106(1):227-234

The microwave spectra of two isotopic species of the unstable molecule difluoroborane have been measured between 8 and 36 GHz. Transitions have been measured up to J = 56 and K_a = 9 for H¹⁰BF₂, and up to J = 66 and K_a = 11 for H¹¹BF₂. Improved values for the rotational constants, boron nuclear quadrupole coupling constants, and quartic and sextic centrifugal distortion constants have been evaluated for both species.     

12.

Measurement of H₂CO hyperfine structure with a two-cavity maser     

S.G. Kukolich  D.J. Ruben 《Journal of Molecular Spectroscopy》1971

Hyperfine structure on the 1₁₀ → 1₁₁ rotational transition in H₂CO was measured using a two-cavity maser spectrometer with 0.3 kHz resolution. The measured spin-rotation constants are C(1₁₀) = −0.80 ± 0.05 kHz and C(1₁₁) = −3.07 ± 0.05 kHz. The hydrogen spin-spin interaction strength is D = 17.74 ± 0.10 kHz. The line center is at 4 829 659.89 ± 0.12 kHz. Properties of the beam source and computer line resolving methods are discussed briefly.     

13.

Electric dipole moments and nuclear hyperfine interactions for H₂S,HDS, and D₂S     

R. Viswanathan  T.R. Dyke 《Journal of Molecular Spectroscopy》1984,103(2):231-239

Electric dipole moments and nuclear hyperfine coupling constants for several low-energy rotational states of the ground vibrational state of H₂S, HDS, and D₂S have been determined by molecular beam electric resonance spectroscopy. Analysis of the Stark effects for radiofrequency spectra of the lowest rotational levels gives dipole moments of 0.978325 (10) D for H₂S (J = 1, τ = 0), 0.977294 (20) D for D₂S (J = 1, τ = 0), and 0.977484 (60) D for HDS (J = 1, τ = 1 and J = 2, τ = 0). The electric field gradient tensor at the deuterium nucleus, the nuclear spin-spin tensor, and the spin-rotation tensor were evaluated from the hyperfine components of the radiofrequency spectra. The accuracy of these tensors was moderately improved over earlier measurements. From the H₂S spin-rotation tensor, the average paramagnetic shielding for the protons was found to be σ_av^p = ?104.84 (40) ppm. Combining this result with the proton NMR absolute chemical shift allowed the average diamagnetic shielding to be calculated as σ_av^d = 135.7 (5) ppm.     

14.

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.     

15.

Microwave spectrum of 2-chloropyridine     

R.T. Walden  Robert L. Cook 《Journal of Molecular Spectroscopy》1974,52(2):244-250

The microwave spectrum of 2-chloropyridine, C₅H₄NCl, has been studied in the frequency range from 26.5–40.0 GHz. The spectrum is characterized by strong parallel type transitions of a near-prolate asymmetric top. The assigned transitions have been used to evaluate the ground state rotational constants of the two chlorine isotopes. The rotational constants are (in MHz): A = 5872.52, B = 1637.83, C = 1280.48 for the ³⁵Cl isotopic species and A = 5872.16, B = 1591.76, C = 1252.17 for the ³⁷Cl isotopic species. The small inertial defect indicates the molecule is planar. In addition an excited vibrational state of C₅H₄N³⁵Cl has been observed and analyzed. The chlorine quadrupolar coupling constants were determined for the ground state and are: χ_aa = ?71.9 MHz for ³⁵Cl and χ_aa = ?54.9 MHz for ³⁷Cl. By assuming the pyridine ring structure the CCl bond length is found to be 1.72 Å.     

16.

Microwave substitution structure of the amine group in Ortho-chloroaniline,C₆H₄CINH₂     

A. Nonat  A. Bouchy  G. Roussy 《Journal of Molecular Spectroscopy》1984,108(2):230-239

The microwave spectra of amine deuterated species of [2-³⁵Cl] and [2-³⁷-Cl]aniline, C₆H₄ClNH₂, have been observed. The rotators associated with the first two states of the amino group inversion have been assigned. A geometric structure has been calculated from the moments of inertia of all isotopic species in the ground state, indicating a small out-of-plane angle (34.5°), and a torsion around the CN bond of the NH₂ group. This deformation is explained by the formation of a hydrogen bond NH … Cl.     

17.

Reaction products from a discharge of N₂ and H₂S: The microwave spectrum of NH₂SH     

F. J. Lovas  R. D. Suenram  W. J. Stevens 《Journal of Molecular Spectroscopy》1983,100(2):316-331

Thiohydroxylamine has been identified as one of the reaction products from the discharge reaction of N₂ + H₂S. Both cis and trans conformers have been observed. The rotational spectra have been studied from 56 to 170 GHz for the normal species and several deuterated isotopic species of each conformer. The electric dipole moments of both conformers have been determined. A number of the transitions of the cis conformer exhibit splittings due to the nuclear quadrupole moment of the ¹⁴N nucleus. A least squares fit of the frequency splittings have led to an analysis of the eQq values. Ab initio calculations using a 4-31G basis set both with and without polarization functions have been carried out to aid in the analysis and to provide a final structural comparison with the microwave results.     

18.

Acetylene spectra with a tunable diode laser: (ν₄ + ν₅)⁰⁺−ν₄^1fQ branches of ¹²C₂H₂ and ¹²C¹³CH₂     

S.Paddi Reddy  V. Malathy Devi  A. Baldacci  W. Ivancic  K. Narahari Rao 《Journal of Molecular Spectroscopy》1979,74(2):217-223

The rotational structure of the Q branches of the (ν₄ + ν₅)⁰⁺?ν₄^1f bands of ¹²C₂H₂ and ¹²C¹³CH₂ at 13.7 μm has been observed in a natural sample of acetylene by using a tunable diode laser as a source in a high-resolution infrared grating spectrometer equipped with a precision grating drive. Altogether 23 lines from J = 6 to 28 for ¹²C₂H₂ and 15 lines from J = 6 to 20 for ¹²C¹³CH₂ have been identified. The observed full width at half maximum of the resolved lines of these Q branches is very close to the calculated Doppler width. Molecular constants ν₀ + B″, B′ ? B″ ? 2D″, D′ ? D″, and H′ ? H″ have been derived from the measured line positions of the rotational structure.     

19.

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.     

20.

Line positions and intensities for the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O     

C. Camy-Peyret  J.-M. Flaud  J.-Y. Mandin  R.A. Toth 《Journal of Molecular Spectroscopy》1978,70(3):361-373

The intensities of about 90 lines of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O have been measured using a Fourier transform spectrum of natural water vapor. The constants involved in the rotational expansion of the transformed transition moment operators corresponding to these bands have been determined through a fit of these line intensities. The constants obtained are used to compute the whole spectrum of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O providing reliable line positions and intensities. For lines involving perturbed levels a comparison is given with the results obtained for H₂¹⁶O and it is shown that the results for one isotopic species cannot be transferred directly to another one.     

	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

     

The interacting states (020), (100), and (001) of H217O and H218O

A fit of about 350 rotational levels of the (020), (100), and (001) vibrational states has been performed for H₂¹⁷O as well as for H₂¹⁸O leading to the determination of 51 rotational and coupling constants for each isotopic species. The Fermi-type interaction and the two Coriolis-type interactions have been taken into account by appropriate rotation-vibration operators and the v-diagonal part of the Hamiltonian is, for each vibrational state, a Watson-type Hamiltonian. The results are very satisfactory since 87% of the experimental levels are reproduced within 15 × 10^?3 cm^?1.     

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:

Analysis of ν2 of H2Se

The infrared absorption spectrum of ν₂ of H₂Se in the region from 885 to 1347 cm^?1 was obtained with a resolution limit of 0.025 cm^?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 1604 lines for the six isotopomers of H₂Se, including 25 lines for the H₂⁷⁴Se isotopomer, and have analyzed them using Watson's A-reduced Hamiltonian in the I^r rotational representation. Ground state constants for each of the five most abundant isotopomers were obtained from fits of microwave transitions combined with weighted averaged ground state combination differences formed from the infrared bands (010), (020), (100), and (001). Upper state constants for each of the five most abundant isotopomers were obtained from least-squares fits of the spectral lines of ν₂, keeping the ground state constants fixed to the values determined from our ground state fits. An alternate set of ground state constants together with isotopic mass adjustment constants for all six isotopomers was determined by simultaneously fitting all available microwave transitions and infrared ground state combination differences. Keeping this set of ground state constants fixed, a single set of upper state constants and isotopic mass adjustment constants for the ν₂ band was determined by a simultaneous fit of infrared spectral lines from all six isotopomers.     

The rotational a-type sepctra of 15N-labeled diazirine,H2CN2

The rotational a-type spectra of isotopically enriched diazirine isotopomers, H₂¹²C¹⁴N¹⁵N and H₂¹²C¹⁵N₂, have been recorded in the region between 8 and 300 GHZ; the latter isotopomer has been observed for the first time. Using Watson's A-reduced Hamiltonian, the rotational constants and the quartic and some sextic centrifugal distortion constants have been determined for the ground vibrational states.     

Reaction products from a discharge of N2 and H2S: The microwave spectrum of two conformers of sulfur diimide (HNSNH)

The rotational spectra of two conformations of sulfur diimide (HNSNH) are reported. The HNSNH species are produced in a low-pressure microwave discharge of N₂ and H₂S. The microwave spectrum of the normal isotopic form, HNSNH, and dideutro form, DNSND, of the cis,trans and cis,cis forms have been observed. The electric dipole moment components of both forms have been determined. The molecular structures were determined from the experimental rotational constants and from geometry optimized ab initio calculations with 4-31G Gaussian basis sets and CEP-31G basis sets including polarization. The experimentally and theoretically derived molecular properties are found to be in good agreement.     

The microwave spectrum and centrifugal distortion constants of difluoroborane,HBF2

The microwave spectra of two isotopic species of the unstable molecule difluoroborane have been measured between 8 and 36 GHz. Transitions have been measured up to J = 56 and K_a = 9 for H¹⁰BF₂, and up to J = 66 and K_a = 11 for H¹¹BF₂. Improved values for the rotational constants, boron nuclear quadrupole coupling constants, and quartic and sextic centrifugal distortion constants have been evaluated for both species.     

Measurement of H2CO hyperfine structure with a two-cavity maser

Hyperfine structure on the 1₁₀ → 1₁₁ rotational transition in H₂CO was measured using a two-cavity maser spectrometer with 0.3 kHz resolution. The measured spin-rotation constants are C(1₁₀) = −0.80 ± 0.05 kHz and C(1₁₁) = −3.07 ± 0.05 kHz. The hydrogen spin-spin interaction strength is D = 17.74 ± 0.10 kHz. The line center is at 4 829 659.89 ± 0.12 kHz. Properties of the beam source and computer line resolving methods are discussed briefly.     

Electric dipole moments and nuclear hyperfine interactions for H2S,HDS, and D2S

Electric dipole moments and nuclear hyperfine coupling constants for several low-energy rotational states of the ground vibrational state of H₂S, HDS, and D₂S have been determined by molecular beam electric resonance spectroscopy. Analysis of the Stark effects for radiofrequency spectra of the lowest rotational levels gives dipole moments of 0.978325 (10) D for H₂S (J = 1, τ = 0), 0.977294 (20) D for D₂S (J = 1, τ = 0), and 0.977484 (60) D for HDS (J = 1, τ = 1 and J = 2, τ = 0). The electric field gradient tensor at the deuterium nucleus, the nuclear spin-spin tensor, and the spin-rotation tensor were evaluated from the hyperfine components of the radiofrequency spectra. The accuracy of these tensors was moderately improved over earlier measurements. From the H₂S spin-rotation tensor, the average paramagnetic shielding for the protons was found to be σ_av^p = ?104.84 (40) ppm. Combining this result with the proton NMR absolute chemical shift allowed the average diamagnetic shielding to be calculated as σ_av^d = 135.7 (5) ppm.     

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.     

Microwave spectrum of 2-chloropyridine

The microwave spectrum of 2-chloropyridine, C₅H₄NCl, has been studied in the frequency range from 26.5–40.0 GHz. The spectrum is characterized by strong parallel type transitions of a near-prolate asymmetric top. The assigned transitions have been used to evaluate the ground state rotational constants of the two chlorine isotopes. The rotational constants are (in MHz): A = 5872.52, B = 1637.83, C = 1280.48 for the ³⁵Cl isotopic species and A = 5872.16, B = 1591.76, C = 1252.17 for the ³⁷Cl isotopic species. The small inertial defect indicates the molecule is planar. In addition an excited vibrational state of C₅H₄N³⁵Cl has been observed and analyzed. The chlorine quadrupolar coupling constants were determined for the ground state and are: χ_aa = ?71.9 MHz for ³⁵Cl and χ_aa = ?54.9 MHz for ³⁷Cl. By assuming the pyridine ring structure the CCl bond length is found to be 1.72 Å.     

Microwave substitution structure of the amine group in Ortho-chloroaniline,C6H4CINH2

The microwave spectra of amine deuterated species of [2-³⁵Cl] and [2-³⁷-Cl]aniline, C₆H₄ClNH₂, have been observed. The rotators associated with the first two states of the amino group inversion have been assigned. A geometric structure has been calculated from the moments of inertia of all isotopic species in the ground state, indicating a small out-of-plane angle (34.5°), and a torsion around the CN bond of the NH₂ group. This deformation is explained by the formation of a hydrogen bond NH … Cl.     

Reaction products from a discharge of N2 and H2S: The microwave spectrum of NH2SH

Thiohydroxylamine has been identified as one of the reaction products from the discharge reaction of N₂ + H₂S. Both cis and trans conformers have been observed. The rotational spectra have been studied from 56 to 170 GHz for the normal species and several deuterated isotopic species of each conformer. The electric dipole moments of both conformers have been determined. A number of the transitions of the cis conformer exhibit splittings due to the nuclear quadrupole moment of the ¹⁴N nucleus. A least squares fit of the frequency splittings have led to an analysis of the eQq values. Ab initio calculations using a 4-31G basis set both with and without polarization functions have been carried out to aid in the analysis and to provide a final structural comparison with the microwave results.     

Acetylene spectra with a tunable diode laser: (ν4 + ν5)0+−ν41fQ branches of 12C2H2 and 12C13CH2

The rotational structure of the Q branches of the (ν₄ + ν₅)⁰⁺?ν₄^1f bands of ¹²C₂H₂ and ¹²C¹³CH₂ at 13.7 μm has been observed in a natural sample of acetylene by using a tunable diode laser as a source in a high-resolution infrared grating spectrometer equipped with a precision grating drive. Altogether 23 lines from J = 6 to 28 for ¹²C₂H₂ and 15 lines from J = 6 to 20 for ¹²C¹³CH₂ have been identified. The observed full width at half maximum of the resolved lines of these Q branches is very close to the calculated Doppler width. Molecular constants ν₀ + B″, B′ ? B″ ? 2D″, D′ ? D″, and H′ ? H″ have been derived from the measured line positions of the rotational structure.     

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.     

Line positions and intensities for the ν1 + ν2 and ν2 + ν3 bands of H218O

The intensities of about 90 lines of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O have been measured using a Fourier transform spectrum of natural water vapor. The constants involved in the rotational expansion of the transformed transition moment operators corresponding to these bands have been determined through a fit of these line intensities. The constants obtained are used to compute the whole spectrum of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O providing reliable line positions and intensities. For lines involving perturbed levels a comparison is given with the results obtained for H₂¹⁶O and it is shown that the results for one isotopic species cannot be transferred directly to another one.