Gas phase, infrared spectra

Whether the molecule is a prolate or an oblate asymmetric rotor, type A, B or C selection mles result in characteristic band shapes. These shapes, or contours, are particularly important in gas-phase infrared spectra of large asymmetric rotors, whose rotational lines are not resolved, for assigning symmetry species to observed fundamentals. 

I. Spectroscopic Determinations. Gas-phase infrared spectra provide a useful adjunct to vapor pressure measurements in the identification of volatile materials. The cell illustrated in Fig. 9.15 allows the sample to be quantitatively returned to the vacuum line after the spectrum has been obtained, so the process is completely nondestructive. The primary problem with a gas cell is to obtain a vacuum-tight seal between the window material and the cell body this may be accomplished with Glyptal paint or with wax- If the latter is used, it is necessary to warm and cool the alkali halide windows slowly to avoid cracking them due to thermal stress. For this purpose an infrared lamp is handy. The most satisfactory method of attaching windows is O-rings because this allows the easy removal of the windows for cleaning and polishing. 

Quantities concerned with spectral absorption intensity and relations among these quantities are discussed in references [59]—[61], and a list of published measurements of line intensities and band intensities for gas phase infrared spectra may be found in references [60] and [61]. 

Buchler and Harran (5) observed only two vibrational frequencies, 1935 and 600 cm . In their gas-phase infrared spectra. These two frequencies are In reasonable agreement with those reported by Seshadrl (4). 

Vibrational frequencies are from gas-phase infrared spectra (9) measured with a grating spectrometer by Buerger et al. 

Vibrational frequencies are those selected by Shiraanouchl ( ) based on gas-phase infrared spectra (9) and liquid-phase Raman spectra (1 ). Gas-phase frequencies are adopted except for = 122 cm and infrared inactive Vg 688 cm... 

The fundamental vibrations are those observed in the gas-phase Raman spectra by Monostorl and Weber ( ) and the gas-phase infrared spectra by Makl et al. (6) and Chalmers and McKean (7 ). The frequencies are essentially the same as those selected by Shimanouchi (8) who also lists earlier spectral studies. Electron-diffraction studies of the gas were reported by Thornton (9) and Hoffman and Livingston ( 0). The adopted bond length is the average of these two results which differ by only 0.006 A. 

Vibrational frequencies are those selected by Shimanouchi ( ) from gas-phase infrared spectra of Buerger and Ruoff (8). Assignments are based on band contours and isotopic splittings and are consistent with recent liquid-phase Raman spectra (9). 

Vibrational frequencies are from gas-phase infrared spectra of Appelman and Kim ( ) the values are confirmed by IR spectra of HOF isolated in a matrix of Ng (4). Structural parameters are those derived by Pearson and Kim (5) from centrifugal distortion analysis of mm-wave rotational spectra (5, 6) of HOF and DOF. We use the atomic coordinates (5) to derive the... 

Bush, B. and E.L. Barnard. 1995. Gas phase infrared spectra of 209 polychlorinated biphenyl congeners using gas chromatography with Fourier transform infrared detection internal standardization with a 13C-labelled congener. Arch. Environ. Contam. Toxicol. 29 322-326. 

The gas-phase infrared spectra for Np(BHit)tt and Np(BDit)tt are shown in Figure 3. The frequencies and assignments for the... 

The National Institute of Standards and Technology (NIST) has developed the WebBook. This site includes gas phase infrared spectra and mass spectral data for compounds. 

National Institute of Standards and Technology (NIST). This site includes gas phase infrared spectra and mass spectral data, http //webbook.nist.gov/chemistrv/ Integrated Spectral Data Base System for Organic Compounds, National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305-8565, Japan. This database includes infrared, mass spectra, and NMR data (proton and carbon-13). 

The stereoisomers, ephedrine and pseudoephedrine, are precursors for metham-phetamine. The gas-phase infrared spectra of these compounds, separated by using GC-iR spectroscopy, are shown in Figure 8.10. From inspection of these spectra, is it possibie to differentiate these compounds in a forensic sample obtained from a clandestine laboratory ... 

Linder R, Seefeld K, Vavra A, Kleinermanns K (2008) Gas phase infrared spectra of nonaromatic amino acids. Chem Phys Lett 453 1... 

The gas phase infrared spectra of ketene and thioketene have been reported and a few bands of selenoketene have been observed in matrix isolation studies These molecules have C2V symmetry with their rotational axes oriented as shown in Fig. 36. The nine fundamental vibrations factorize such that the totally symmetric vibrations Vj-v belong to the a species, the out-of-plane vibrations Vj and to the bj species, and the in-plane vibrations to the bj species. The a fundamentals give type-A parallel bands, while type-C and type-B perpendicular bands are found for the b, and bj fundamentals, respectively. Since ketene and thioketene are near-prolate symmetric tops, the rotational structure of the IR bands is only minimally complicated by asymmetry splittings. 

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