Flemming M. Nicolaisen

Far-infrared gas spectra of phenol, 4-fluorophenol, thiophenol and some deuterated species: barrier to internal rotation

Abstract The far-infrared gas spectra (400-50 cm−1) are reported for phenol, [7-D]phenol, [4-D]phenol, 4-fluorophenol, 4-fluoro[7-D]phenol and thiophenol. The spectra are assigned and the barrier (V2) to internal rotation is calculated from combined far infrared and microwave data. The results for V2 are (using the same sequence as above): 1213, 1243, 1213, 1007, 1034, 267 cm−1. The origin of the barrier differences is discussed.

Proton magnetic resonance spectra at 220 MHz of amino acids, porcine and bovine insulin and the A and B chains of bovine insulin

Abstract Proton magnetic resonance (PMR) spectra of 21 commonly occurring amino acids dissolved in CF 3 COOH or CF 3 COOD were recorded and analyzed in terms of proton chemical shifts, relative to (CH 3 ) 4 Si (TMS) as internal standard, and proton spin-spin coupling constants. The results were used for an analysis of PMR spectra of insulin and the individual A and B chains (as S -sulfonates), all dissolved in CF 3 COOH or CF 3 COOD. In the unusually high magnetic field applied (ca. 50,000 oersteds) large chemical shifts are found. Resonances from specific protons in arginine, alanine, asparagine, glycine, histidine, lysine, phenylalanine, threonine, and tyrosine residues are observed separately in single recordings. The γ-CH 2 protons of glutamic acid and glutamine residues form one separate band at 2.70 ppm, the CH 3 protons of leucine, isoleucine, and valine form another separate band at 1.00 ppm. Only proton resonances from cysteine, proline, and serine residues give no easily accessible evidence of their presence but they contribute significantly to the intensity versus chemical shift integrals.

An intercomparison of laboratory measurements of absorption cross-sections and integrated absorption intensities for HCFC-22

Abstract An intercomparison of measurements of infra-red absorption cross-sections and integrated absorption intensities in HCFC-22 has been carried out. Independent measurements were made by five spectroscopy groups so that their experimental methods and data reduction techniques could be critically examined. The initial results showed a spread in reported values for integrated absorption intensity over the mid infra-red spectral region that were larger than the reported uncertainties. Re-examination of experimental and data reduction methods resulted in consistency of results within the reported errors. It was found that particular attention had to be paid to controlling and characterising errors associated with the non-linear response of MCT detectors and pre-amplifiers, adsorption of the sample on surfaces in the absorption cell, effectiveness of mixing when making measurements on mixtures of absorber gas and a buffer gas, and location of the photometric “full-scale” and “zero” levels.

Vibrational spectra of 1,3,5-hexatriene and methylated derivatives

Abstract The ground state vibrational spectra of E -hexatriene, Z -hexatriene, E,E -heptatriene, E,E,E -octatriene, and E -2,5-dimethyl-hexatriene are reported. For E - and Z -hexatriene complete vibrational assignments, and for heptatriene, octatriene, and dimethyl-hexatriene near-complete assignments are obtained. The effects of terminal and lateral methyl-substitution are compared.

Infrared spectra of nitrosyl cyanide and 8 isotopically substituted species. A general harmonic force field determined from experimental data and ab initio calculations

Abstract Infrared gas phase spectra of ONCN, ONC 15 N, ON 13 CN, O 15 NCN, 18 ONCN, O 15 NC 15 N, O 15 N 13 CN, 18 ONC 15 N and 18 ON 13 CN have been recorded. A general harmonic force field (with six constraints) has been derived based on the assigned fundamental vibration frequencies and checked by calculation of experimental values for centrifugal distortion constants, a Coriolis coupling constant and the inertial defect. The harmonic force field of a fully optimized structure of ONCN as found by the Pulay force method is reported and compared to the experimental force field. No essential disagreements were found.

Coriolis perturbations in the ν10, ν7, ν4, ν12 band system of trans-d2-ethylene

Abstract The effect of a -, b -, and c -axis Coriolis perturbations in the infrared spectrum of the band system ν 10 , ν 7 , ν 4 , ν 12 of trans-d 2 -ethylene has been studied at a resolution near 0.03 cm −1 . From a global analysis of this band system taking into account Coriolis resonances, spectroscopic constants for each of the vibrations are derived as well as second-order Coriolis interaction constants for ν 10 and ν 7 .

The high-resolution infrared spectrum of ethylene-d4 below 1200 cm−1

Abstract The IR spectrum of the fundamental bands ν 12 , ν 7 , and ν 10 in ethylene- d 4 at 1077, 720, and 593 cm −1 , respectively, has been recorded with a resolution of ca. 0.03 cm −1 . The three bands have been analyzed simultaneously from a model taking into account all first-order Coriolis resonances within the tetrad ν 12 , ν 4 , ν 7 , ν 10 . In addition, second-order a -Coriolis resonance between ν 7 and ν 10 and third-order b -Coriolis resonance between ν 4 and ν 10 , which both give rise to local perturbations, have been included. The analysis yields a set of spectroscopic constants for the three bands. Furthermore, the band center and the rotational constants for the inactive ν 4 level have been determined from its perturbing effect on ν 7 and ν 10 . A ground state combination difference analysis of ν 12 and ν 7 yields the following ground state rotational constants: A 0 = 2.441656(20) cm −1 , B 0 = 0.734913(6) cm −1 , and C 0 = 0.563517(6) cm −1 .

Coriolis perturbations in the infrared spectrum of the ν4 + ν7 and ν7 + ν8 bands of cis-d2-ethylene

Abstract The infrared spectra of the ν 4 + ν 7 and ν 7 + ν 8 type a combination bands of cis -C 2 H 2 D 2 at 1816 and 1599 cm −1 , respectively, have been recorded with a resolution of ca. 0.03 cm −1 . Both bands are locally perturbed by a number of Coriolis resonances with nearby binary combination levels. From a model taking into account Coriolis interactions with ν 6 + ν 8 and ν 6 + ν 7 spectroscopic constants have been obtained for ν 4 + ν 7 . For the analysis of ν 7 + ν 8 Coriolis resonance with ν 2 has been included. None of the perturbing levels have been observed. However, from the perturbation effect alone the band centers for ν 6 + ν 8 , ν 6 + ν 7 , and ν 2 have been located.

Infrared spectra and vibrational assignment of tricarbon oxide sulphide, C3OS. Calculations of normal modes and valence force constants

Abstract The infrared spectra in the region 4000—200 cm −1 of gaseous and solid tricarbon oxide sulphide, C 3 OS, are reported. A calculation of normal frequencies using a force field transferred from C 3 O 2 and C 3 S 2 is carried out, and a primitive valence force field reproducing the observed frequencies, together with drawings of the normal/modes, are presented.

The infrared spectrum of gaseous cis-d2-ethylene below 1400 cm−1

Abstract Three infrared active fundamental bands of cis-d 2 -ethylene have been studied at a resolution of ca. 0.030 cm −1 : the type- c band ν 7 and the two type- a bands ν 6 and ν 12 . From a simultaneous analysis of infrared ground state combination differences due to ν 7 together with microwave measurements, a set of ground state rotational and centrifugal distortion constants has been obtained. For all three bands upper state spectroscopic constants are determined, and perturbations are identified. The K ′ a = 4 level in ν 7 is perturbed locally by a higher order c -Coriolis resonance with ν 8 . ν 6 is globally perturbed by first-order a -Coriolis resonances with ν 4 and ν 8 . For ν 12 a higher order c -type Coriolis resonance with 2 ν 10 is of importance for several K a levels, and the constants for ν 12 have been obtained taking this interaction into account. In addition, a Coriolis resonance parameter and some constants for 2 ν 10 have been determined.