Manfred Winnewisser

Millimeter‐Wave Rotational Spectrum of HSSH and DSSD. I. Q Branches

The Q‐branch rotational lines of H2S2 have been measured in the frequency range 80–200 Gc/sec, those of D2S2, in the range from 60 to 220 Gc/sec. For HSSH, measurements were made on the torsional vibrational state υtu2009=u20091, and the S–S bond‐stretching vibrational state υsu2009=u20091 as well as on the ground state. The molecules are the most nearly accidentally symmetric tops of any so far reported. Wangs asymmetry parameter bpu2009=u2009(Cu2009−u2009B)u2009/u2009(2Au2009−u2009Bu2009−u2009C) for the ground vibrational state of H32S32SH is found to have the value bpu2009=u2009−u20091.10u2009×u200910−5; for H32S34SH, bpu2009=u2009−u20091.07u2009×u200910−5; for D32S32SD, bpu2009=u2009−u20092.10u2009×u200910−6. The asymmetry increases markedly with the torsional oscillation: for H32S32SH when υtu2009=u20091, bpu2009=u2009−u20094.055u2009×u200910−5; it decreases with the S–S stretching: for H32S32SH when υsu2009=u20091, bpu2009=u2009−u20097.72u2009×u200910−6. The molecule is found to have the nonplanar chain structure HSSH, with the structural parameters having the values: dSHu2009=u20091.327 A, dSSu2009=u20092.055 A, ∠HSSu2009=u200991.32°, and the dihedral angle ηu2009=u200990°36′. The barrier to relat...

The millimeter wave spectra of isocyanic and isothiocyanic acids

Abstract An investigation of the mm-wave rotational spectra of the very slightly asymmetric tops HNCS, DNCS, HNCO and DNCO has been carried out in the frequency range 80 000–190 000 Mc/sec. Several R -branch, a -type, transitions were observed for each molecule and the rotational constants A 0 , B 0 , and C 0 were determined for the four species containing the most abundant isotopes of N, C, O, or S. B 0 and C 0 were also found for HNCS 34 . The centrifugal distortion constant D J was obtained for each abundant form. The constants are HNCS: A 0 = 1 483 000 ± 167 000 Mc/sec, B 0 = 5883.42 ± 0.02 Mc/sec, C 0 = 5845.62 ± 0.02 Mc/sec, D j = 1.17 ± 0.05 Kc/sec; DNCS: A 0 = 723 400 ± 25 000 Mc/sec, B 0 = 5500.51 ± 0.05 Mc/sec, C 0 = 5445.26 ± 0.05 Mc/sec, D j = 1.22 ± 0.31 Kc/sec; HNCS 34 : B 0 = 5744.81 ± 0.20 Mc/sec, C 0 = 5708.73 ± 0.20 Mc/sec; HNCO: A 0 = 956 400 ± 50 000 Mc/sec, B 0 = 11 071.02 ± 0.05 Mc/sec, C 0 = 10 910.58 ± 0.05 Mc/sec, D j = 3.5 ± 0.5 Kc/sec; DNCO: A 0 = 534 500 ± 70 000 Mc/sec, B 0 = 10 313.61 ± 0.05 Mc/sec, C 0 = 10 079.67 ± 0.05 Mc/sec, D j = 2.9 ± 0.5 Kc/sec. The centrifugal distortion K -pattern is different in character for each of the four molecules. Agreement between calculation and experiment is obtained for HNCO and DNCO with the additional constants; HNCO; D JK = +837 Kc/sec, H JJK = −0.056 Kc/sec, H JKK = +2.81 Kc/sec. DNCO: D JK = −227.1 Kc/sec, H JJK = +0.15 Kc/sec, H JKK = −5.61 Kc/sec, H JJJ = 0, utilizing the expression given by Costain. This expression gives a poor fit for DNCS and no fit for HNCS, and at present no treatment has been found to fit or explain satisfactorily the K -patterns for these two molecules. An improved molecular structure has been calculated for HNCS the structural parameters being revised to r (Hue5f8N) = 0.988 7 ± 0.003 A, r (Nue5f8C) = 1.216 4 ± 0.007 A, r (Cue5f8S) = 1.560 5 ± 0.003 A A number of lines due to rotational transitions of vibrationally excited molecules were also observed and are assigned to the states v 5 = 1 and v 6 = 1 for HNCS and HNCO and probably, in addition, v 4 = 1 for DNCS.

The bending-rotation spectrum of fulminic acid and deuterofulminic acid☆☆☆

Abstract A quasilinear molecular model is needed to account for the infrared absorption spectrum of HCNO and DCNO in the spectral region from 100 cm −1 to 1000 cm −1 . The observed systems of infrared bands arising from the ν 5 vibrational manifold have all been assigned. The rotational structure of the absorption bands at 225 cm −1 , 275 cm −1 , 315 cm −1 , and 317 cm −1 for HCNO has been resolved using a Fourier spectrometer. The rotational constants and the band centers have been determined for the above bands, which represent the transitions (0000 0 1 1 ) c ←0000 0 0 0 (0000 0 2 2 ) c,d ←(0000 0 1 1 ) c,d both components (0000 0 3 3 ) c,d ←(0000 0 2 2 ) c,d 0000 0 2 0 ←(0000 0 1 1 ) c . By means of the Ritz combination principle the infrared transitions could be used to build up the vibrational energy level scheme of the ν 5 vibrational mode for HCNO and DCNO. The data are only reconcilable with a potential function for ν 5 which exhibits a low barrier opposing linearity. Preliminary values of the potential parameters were obtained using different approximate theoretical approaches. A reinterpretation of the r 8 structure parameters of fulminic acid in the light of the quasilinear model leads to an explanation of the extraordinarily short CH internuclear distance of 1.027 A as the projection of a CH bond length of 1.060(5) A upon the heavy-atom axis. The isotopic shift upon deuteration observed in the infrared data indicate that the ν 5 fundamental vibration is primarily an HCN bending motion. The ν 4 fundamental vibration (skeletal bending motion) of HCNO is located at 537 cm −1 and does not exhibit any hot band structure which would be indicative of a perturbed potential function.

Centrifugal Distortion Effects and Structure of Hydrazoic Acid from the Millimeter Wave Rotational Spectra

The rotational spectra of two 15N‐substituted species of hydrazoic acid have been investigated. The values of the rotational constants are: H15N14N14N:u2009u2009A0=619u2009916u2009u2009u2009Mc/sec,B0=u200911u2009667.54u2009Mc/sec,C0=u200911u2009427.86u2009Mc/sec, H14N14N15N:u2009u2009A0=616u2009868u2009u2009u2009Mc/sec,B0=u200911u2009641.76u2009Mc/sec,C0=u200911u2009405.08u2009Mc/sec. With the aid of the rotational constants for H14N3 and D14N3 the following structural parameters were obtained: r(N1–H)u2009=0.975±0.015u2009A,r(N1–N2)u2009=1.237±0.002u2009A,r(N2–N3)u2009=1.133±0.002u2009A,∠HN1N2=114∘u20097.8′±30′. An important part of this study was the investigation of the centrifugal stretching behavior exhibited by HN3 and its isotopic species. It has been found that even at low J the introduction of P6 distortion terms for higher K—1 transitions is essential to accurately account for the observed rotational frequencies.

Millimeter Wave Spectroscopy of Unstable Molecular Species. I. Carbon Monosulfide

The carbon monosulfide species CS32 and CS34 are investigated with a millimeter wave spectrometer designed for the study of short‐lived molecules in the frequency range from 60 000 to 300 000 Mc/sec. Spectroscopic constants obtained are: u2009u2009u2009u2009u2009u2009u2009u2009u2009u2009CS32u2009u2009u2009u2009u2009u2009u2009u2009u2009u2009CS34B0=24 495.592±0.006u2009Mc/secB0=24 103.554±0.006u2009Mc/secBe=24 584.367±0.006u2009Mc/secDe=0.03979±0.0017u2009Mc/secαe=117.550±0.012u2009Mc/secHe=0.0625±0.009u2009kc/secDe=0.04285±0.00166u2009Mc/secHe=0.0653±0.0085u2009kc/sec The spectrometer is described. Its sensitivity has been estimated to be the order of 10—5 to 10—6 cm—1.

Millimeter Wave Spectroscopy of Unstable Molecular Species. II. Sulfur Monoxide

Several spectral transitions of the gaseous free radical SO have been observed in the millimeter wave region. Analysis of the observed lines confirms that the molecule has a 3Σ ground state and leads to the rotational constants B0=21 523.75 Mc/sec and D0=0.0334 Mc/sec, also to the magnetic coupling constants λ=158 209.4 Mc/sec and γ=—164.52 Mc/sec. The assignments and analysis are confirmed by a close fitting, within approximately 1 Mc/sec, of all measured and calculated frequencies, and by the Zeeman effect which is measured and analyzed for several transitions.

Microwave and millimeter wave spectra of hydrazoic acid

Abstract Five rotational transitions have been recorded for each of the abundant species of hydrazoic acid and hydrazoic acid-d. Both molecules have normal centrifugal distortion behavior. The spectroscopic constants derived from the measurements are HN 3 −A 0 = 615,600 ± 7000 Mc/sec, B 0 = 12,034.15 ± 0.09 Mc/sec, C 0 = 11,781.51 ± 0.09 Mc/sec, D JK = 787.8 ± 5.4 kc/sec, D J = 5.09 ± 0.54 kc/sec, H JKK = −1.13 ± 0.15 kc/sec, H JJK - 0.03 ± 0.03 kc/sec. DN 3 −A 0 = 351,500 ± 7000 Mc/sec, B 0 = 1,350.23 ± 0.05 Mc/sec, C 0 = 10,965.48 ± 0.05 Mc/sec, D JK = 442.6 ± 2.4 kc/sec, D J = 4.22 ± 0.17 kc/sec, H JKK = − 0.21 ± 0.08 kc/sec, H JJK = − 0.03 ± 0.02 kc/sec. An important part of the study was a reinvestigation of the J = 0 → 1 transition of HN 3 which gave eq aa Q = 4.65 ± 0.25Mc/sec for the NH nitrogen N 14 nucleus.

The vibrational energy manifold of the lowest lying bending mode of tricarbon oxide sulfide, OCCCS, as determined by relative intensity measurements

Abstract The determination of a precise vibrational energy level scheme for the two-dimensional bending mode of tricarbon oxide sulfide (3-thioxo-1,2-propadiene-1-one), Oue5fbCue5fbCue5fbCue5fbS, has been carried out by relative intensity measurements of rotational transitions up to the seventh excited vibrational state of ν 7 . The harmonic wavenumber ω 7 was determined to be 84.50 ± 0.63 cm −1 while the anharmonicity constant χ 77 was found to be −0.62 ± 0.11 cm −1 , respectively. A linear dependence of the expectation value of the electric dipole moment on the vibrational quantum number υ 7 was found. All results confirm that in Oue5f8 Cue5fbCue5fbCue5fbS the potential function describing the two-dimensional oscillator of ν 7 is very harmonic without a perturbing barrier to linearity as was found in the case of Oue5fbCue5fbCue5fbCue5fbO.

High-resolution spectrum of the ν1 fundamental band of isocyanic acid, HNCO

Abstract The ν 1 fundamental band of HNCO has been recorded with high resolution using a Bomem FTIR spectrometer. The spectrum is so strongly perturbed by accidental resonances that a global fit using an effective Hamiltonian for asymmetric rotors has not been successful. The molecular parameters including the band origin have been determined by analyzing each K a substate separately. The combination differences for the ground state allowed us to improve the ground state spectroscopic constants.

The vibrational force field of diazirine from gas phase data and from ab initio calculations

Abstract Vibrational band centers from five isotopic species (parent species H 2 CN 2 , all symmetrically substituted species and HDCN 2 ), centrifugal distortion constants also from five isotopic species (parent species, all symmetrically substituted species and H 2 C 15 NN), and information about the Fermi resonance between ν 2 and 2ν 7 from matrix data have been combined to obtain an experimental force field of diazirine. Since diazirine represents an unusual bonding situation, an ab initio force field was also determined. The uniqueness of the transformation from cartesian to valence coordinates is discussed. Information from the ab initio force field was used in obtaining an optimal force field from the experimental data.