Near Infrared Absorption of Pure Carbon Dioxide up to 3100 bar and 500 K. I. Wavenumber Range 3200 cm-1 to 5600 cm-1
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Abstract:
Near infrared absorption of pure CO 2 in the v 1 + v 3 , 2v 2 0 + v 3 Fermi diad region around 3650 cm -1 and in the 2v 1 + v 3 , v 1 + 2v 2 0 + v 3 , 4v 2 0 + v 3 Fermi triad region around 5000 cm -1 was measured at temperatures between 298 K and 500 K to a maximum pressure of 3100 bar. Density tuning of Fermi resonance is studied and compared with literature data on gaseous, liquid, and solid CO 2. Band maximum positions determined within an extended temperature and density range indicate appreciable rotational freedom up to about the critical density (0.45 g · cm -3 ) and repulsive interactions clearly coming into play above 0.9 g · cm -3 . The vibrational intensity of the Fermi triad, up to about 1.0 g · cm -3 is found to be independent of temperature and pressure within ± 2.5%, wich enables (pure) CO 2 concentrations in a large region of states to be precisely and directly measured via quantitative high-pressure high-temperature near infrared spectroscopy.Keywords:
Diad
Fermi resonance
Bar (unit)
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Atmospheric temperature range
Abstract Constant‐composition copolymers of methyl methacrylate and vinylidene chloride produced by radical copolymerization are studied by 1 H‐NMR at 60 and 250 MHz. The different methods of the literature for the derivation of reactivity ratios from either the copolymer composition or the sequence average lengths, or even the diad distribution, are applied but lead to rather dispersed results. A new graphical method is proposed, based on the use of peculiar values of the triad distribution functions. It allows us to detect a penultimate effect for the vinylidene chloride‐rich region. In the same range, a change in tacticity of the diads and triads on the methylmethacrylate sequences, as compared with homopolymers, is observed; it suggests that the anomaly is caused by the competition of the depropagation reaction.
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Abstract Samples of poly[( m ‐phenylene terephthalate)‐ co ‐oxybenzoate] with different compositions were analyzed by 13 C NMR spectroscopy. Diad and triad signals could be identified and assigned. Furthermore, the signals of acetoxy, carboxy and hydroxy end‐groups were assigned. The analysis of NMR substituent effects confirms the assignment. Comparison of the calculated statistical with the experimentally determined diad and triad contents shows a slight tendency for the formation of oxybenzoate blocks in the polymer chain.
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Proton NMR
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The vibration-rotation structure of the infrared absorption bands due to ν21+ν3, 2ν20+ν3, and ν1+ν3 have been observed and measured for Br79CN and Br81CN. The average value of α3 for these two isotopic molecules was found to be +0.000677 cm—1. The Fermi resonance constant for the resonance diad was calculated to be W12=35.41 cm—1 for Br79CN and W12=35.48 cm—1 for Br81CN. The positions of the Q branches of a number of other bands were also measured.
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Abstract The DMSO solution copolymerization of acrylonitrile and vinylidene chloride can be adequately described by the terminal‐unit copolymerization model. The sequence distribution measured by 13 C‐NMR is in excellent agreement with the theoretically calculated diad, triad, and pentad distributions. The variation of glass transition temperatures with copolymer composition is explained by sequence distribution.
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Regioregular poly(propylene oxide), PPO, formed by simple base (KOH) and coordinate base (TPP)AlCl, (tetraphenylporphinato)aluminum chloride, ring-opening polymerization of propylene oxide, PO, has been studied by high field 13C{1H} NMR spectroscopy at various concentrations in CDCl3 and C6D6. The original assignments of Tonelli and Schilling [Macromolecules 1986, 19, 1337−1343] at the triad and diad sensitivity level have been extended to tetrad sensitivity.
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Tacticity
Comonomer
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Vinyl polymer
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Absorption bands of carbon dioxide involving the Fermi diads 10°0, 02°0 and 10°1, 02°1 have been investigated and molecular constants obtained. The variation in the centrifugal stretching constants which has been observed in the component levels is such that the average centrifugal stretching constant of the diad is very nearly the same as that of the vibrationless ground state of CO2.
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Fermi resonance
Force constant
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Triad (sociology)
Isobutylene
Reactivity
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Abstract 13 C NMR spectra of poly(methyl vinyl ketone)s (PMVK) and poly(isopropenyl methyl ketone)s (PIPMK) obtained by radical and anionic catalysts were measured. The 13 C resonances of the CH 2 carbon of PMVK were tentatively assigned to diad tacticities. The spectra of carbonyl carbon and methyl carbon of the CH 3 CO group of PIPMK were assigned to pentad and triad tacticities, respectively. It is shown that radically obtained PMVK and PIPMK have atactic and syndiotactic‐rich structure, respectively. The stereoregularity of radically obtained PIPMK obeys Bernoullian statistics, while that of anionically obtained PIPMK conforms to first‐order Markov statistics.
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Tacticity
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Methyl vinyl ketone
Carbon fibers
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Fermi resonance
Vibronic spectroscopy
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