B. P. Winnewisser

On the high resolution infrared spectrum of HCNO

Abstract The ν 1 fundamental of HCNO has been measured with a resolution of 0.05 cm −1 . Although the molecule is unstable, conditions have been established making it possible to measure the high resolution infrared absorption spectrum. The ground state rotational constant B 0 obtained from the ν 1 band agrees with the value obtained from the microwave work within the accuracy of infrared data.

Substitution structure of cyanogen, NCCN, from high-resolution far infrared spectra☆

Abstract The lowest lying vibrational bands of the gas-phase spectra of cyanogen, NCCN, and four of its isotopomers, 15 NCCN , N 13 CCN , 15 NCC 15 N , and N 13 C 13 CN , were recorded with a Fourier transform interferometer. The resolution was limited by the maximum optical path difference (MOPD) attainable with the interferometer to FWHM =0.0012 cm −1 . Rovibrational transitions of the ν 5 ( ≈230 cm −1 ) and also the ν 2 – ν 5 ( ≈610 cm −1 ) band systems were assigned for all five isotopomers. The use of an effective Hamiltonian for linear molecules to fit the data yielded precise spectroscopic vibrational and rotational constants for the vibrational states ( v 1 v 2 v 3 v 4 v 5 ) or ( v 4 v 5 )=(00), (01), (02), (03), and (01000). These data include the first rotationally resolved transitions involving (01000). Complete substitution ( r s ) structures of cyanogen, based on both single and double isotopic substitution of the parent species, were calculated. The derived structure is r CC =138.48(17)xa0pm and r CN =115.66(13)xa0pm. The two r s structures coincide within the errors due to remaining contributions of zero-point vibrations.

Ritz assignment and Watson fits of the high-resolution ring-puckering spectrum of oxetane

Abstract Oxetane is a four-membered ring molecule exhibiting a large-amplitude ring-puckering motion. In order to analyze this vibration we recorded a rotationally resolved far-infrared spectrum between 50 and 145xa0cm−1. The analysis of the ring-puckering fundamental band with the assignment of 1108 lines, has been presented in a previous paper. In the present work we present a list of further 6531 assigned transitions between the five lowest excited ring-puckering states. The 4983 term values involved in the transitions assigned in this and in the preceding work have been evaluated by the “Ritz” program, and are now available. An A-reduced Watson Hamiltonian in any of the three representations Ir, IIr, and IIIr was used to perform a fit of the assigned transitions. Precise rotational constants and quartic as well as a full set of sextic centrifugal distortion constants were obtained for the investigated ring-puckering states. For the first time, high-resolution values for the vibrational Gv parameters have been obtained, and we have added terms in x6 and x8 to the double minimum-potential well describing the ring-puckering motion, in order to reproduce their values within the experimental accuracy. The same potential still reproduces the lower resolution values of the Q-branch origins involving higher ring-puckering states up to vrp=14 found in the previous literature.

Far-infrared spectrum of S(CN)2 measured with synchrotron radiation: global analysis of the available high-resolution spectroscopic data.

The high resolution Fourier transform spectrum of the chemically challenging sulfur dicyanide, S(CN)2, molecule was recorded at the far-infrared beamline of the synchrotron at the Canadian Light Source. The spectrum covered 50-350 cm(-1), and transitions in three fundamentals, ν4, ν7, and ν8, as well as in the hot-band sequence (n + 1)ν4 - nν4, n = 1-4, have been assigned and measured. Global analysis of over 21,300 pure rotation and rotation vibration transitions allowed determination of precise energies for 12 of the lowest vibrationally excited states of S(CN)2, including the five lowest fundamentals. These results constitute an extensive set of benchmarks for ab initio anharmonic force field calculations and the observed and calculated vibration-rotation constants and anharmonic frequencies are compared. The semiexperimental equilibrium, r(e)(SE), geometry of S(CN)2 has also been evaluated. In the course of the measurements, new information concerning the physical chemistry of S(CN)2 has been obtained.

The Infrared Spectrum of CH3OH: Evidence for State Mixings

In the framework of our systematic investigation project of the infrared and far infrared spectrum of CH3OH by high resolution Fourier transform spectroscopy, we have currently assigned more than 35000 absorption lines. Two listings of 12700 assigned lines below 200 cm-1 have already been published1,2, and a listing of almost 8700 lines between 200 and 350 cm-1 is in press.

The Methanol Absorption Spectrum between 350 and 1250 cm-1

The whole absorption spectrum of CH3OH between 30 and 1250 cm-1 has been measured on the prototype instrument of the Bruker Fourier transform spectrometer at the Physical Chemistry Institute of the University of Giessen.