Microwave Spectrum of 1-Cyano-3-fluoro-but-1-ene

The rotational spectrum of the 1-cyano-3-fluoro-but-1-ene has been recorded with a pulsed-nozzle microwave Fourier transform spectrometer over the range 6-20 GHz. The frequencies were fitted to the Hamiltonian of Watson (A-reduction, I(r) representation). The resulting rotational constants are A = 7493.404(1) MHz, B = 1211.9831(2) MHz, and C = 1096.0908(1) MHz. By comparing the experimental rotational constants with those obtained by ab initio calculations, we found without ambiguity that the stable conformation for the molecule is the one with the fluorine atom lying in the C&bond;CCN plane (CF-eclipsed conformer). Copyright 2000 Academic Press.     

Electronic states of neutral and ionized tetrahydrofuran studied by VUV spectroscopy and ab initio calculations

The electronic spectroscopy of isolated tetrahydrofuran (THF) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 5.8–10.6 eV with absolute cross-section measurements derived. In addition, an electron energy loss spectrum was recorded at 100 eV and 10° over the 5–11.4 eV range. The He(I) photoelectron spectrum was also collected to quantify ionisation energies in the 9–16.1 eV spectral region. These experiments are supported by the first high-level ab initio calculations performed on the excited states of the neutral molecule and on the ground state of the positive ion. The excellent agreement between the theoretical results and the measurements allows us to solve several discrepancies concerning the electronic state spectroscopy of THF. The present work reconsiders the question of the lowest energy conformers of the molecule and its population distribution at room temperature. Electronic supplementary material  Supplementary Online Material     

Ab initio and experimental study of the K-shell spectra of 2,5-dihydrofuran

The K-shell spectra of gaseous 2,5-dihydrofuran at the carbon and oxygen thresholds are reported for the first time. They have been measured using the inner-shell electron energy loss spectroscopy (ISEELS) method. Ab initio Configuration Interaction calculations have been carried out to assign the observed bands. The O1s spectrum is similar to that of tetrahydrofuran and the assignments of the bands are close to those obtained in the case of furan, excepting the furan first π* band. At the C1s edge, the spectrum differs from the furan case, because of the different chemical environment of one of the non-equivalent carbon atoms: due to the presence of hydrogen atoms out of the carbon–oxygen ring plane, several Rydberg core excited states have an important valence character, leading to large intensities in the experimental spectrum.     

Topochemical aspects of elementary reactions of the emulsion polymerization of acrylonitrile

A combination of statistic and kinetic methods of analysis is used to collect quantitative data on the kinetics of elementary reactions of growth and termination of kinetic chains in each phase of a heterophase system as well as on interfacial mass exchange at the quasistationary stage of radiation-induced emulsion polymerization of acrylonitrile. It is found that, in the system, a steady-state concentration of polymer—monomer particles is attained, and these particles are able to increase their dimensions with an increase in monomer conversion. Activation of particles and chain termination on particles are due to the entrapment of macroradicals from water. As a result of a gradual increase in the dimensions of polymer-monomer particles and a decrease in the monomer concentration in the aqueous phase, the adsorption layer of acrylonitrile becomes so thin that, at the final stage, monomolecular layers lose integrity and the conditions of quasi-stationarity are violated.     

Graft polymerization of acrylic acid onto powdered polyethylene

Radiation-induced graft polymerization of acrylic acid onto powdered polyethylene samples of various granulometric compositions was studied. The resulting graft polymer can be used as a cation-exchange sorbent. The ion adsorption properties of the synthesized cation exchanger were characterized.     

Caloric curves and energy fluctuations in the microcanonical liquid-Gas phase transition

In this paper we study a microcanonical lattice gas model with a constrained average volume. We show that the caloric curve explicitly depends on the considered transformation of the volume with the excitation energy and so does not bear direct information on the characteristics of the phase transition. Conversely, partial energy fluctuations are demonstrated to be a direct measure of the equation of state. Since the heat capacity has a negative branch in the phase transition region, the presence of abnormally large kinetic energy fluctuations is a signal of the liquid-gas phase transition.     

Effects of synthesis conditions and the mechanism of homopolymerization of acrylonitrile on the thermal behavior of the resulting polymer

The effect of the conditions of polyacrylonitrile synthesis (nature of the solvent, homogeneity of the reaction medium, and type of initiation) on the conditions of formation of the polyconjugation system during the pyrolysis of polyacrylonitrile is studied. The controlled synthesis of polyacrylonitrile via radiation polymerization mediated by dibenzyl trithiocarbonate as a reversible addition-fragmentation chain-transfer agent at 25 and 80°C is performed for the first time. It is shown that the type of initiation in reversible addition-fragmentation chain-transfer polymerization (material initiation or radiolysis) strongly affects the structure of the formed polyconjugation system.     

Electronic states of F2CO as studied by electron energy-loss spectroscopy and ab initio calculations

This paper reports on the first measurements of the electron impact electronic excitation cross-sections for carbonyl fluoride, F(2)CO, measured at 30 eV, 10° and 100 eV, 5° scattering angle, while sweeping the energy loss over the range 5.0-18.0 eV. The electronic-state spectroscopy has been investigated and the assignments are supported by quantum chemical calculations. The energy bands above 9.0 eV and the vibrational progressions superimposed upon it have been observed for the first time. Vibronic coupling has been shown to play an important role dictating the nature of the observed excited states, especially for the low-lying energy region (6.0-8.0 eV). New experimental evidence for the 6(1)B(2) state proposed to have its maximum at 12.75 eV according to the vibrational excitation reported in this energy region (11.6-14.0 eV). The n = 3 members of the Rydberg series have been assigned converging to the lowest ionization energy limits, 13.02 eV ((2)B(2)), 14.09 eV ((2)B(1)), 16.10 ((2)B(2)), and 19.15 eV ((2)A(1)) reported for the first time and classified according to the magnitude of the quantum defects (δ).     

The vibrational structure of the oxygen K-shell spectra in acenaphthenequinones: an ab initio study

The vibrational structure of the K-shell O1s → π? of acenaphthenequinone C(12)H(6)O(2) and its halogenated compound C(12)H(2)Br(2)Cl(2)O(2) has been simulated using an entirely ab initio approach. For both molecules, analysis of the calculated Franck-Condon factors confirm without ambiguity that, contrary to initial claims, the C-H stretching modes are not modified in the core states and are not excited. For C(12)H(6)O(2), the vibrational fine structure appears to be mainly due to three modes, involving C=O? asymmetric stretch and in-plane ring deformation modes, due to the symmetry breaking of the core state. For C(12)H(2)Br(2)Cl(2)O(2), the vibrational excitation arises essentially from the C=O? asymmetric stretch, with numerous secondary peaks arising from hot and combination bands. For both molecules, these bands are probably responsible for the asymmetry deduced in the experimental fits using a unique Morse potential and initially assigned to anharmonic effects.