Spectra Of Ethylene Research Articles

Carbon K-shell excitation spectra of linear and branched alkanes

The electron energy loss spectra of ethane, propane, n-butane, n-pentane, n-hexane, isobutane, isopentane and neopentane in the region of carbon K-shell excitation have been recorded under dipole-dominated conditions (2.8 ke V impact energy, small angle). The spectra are dominated by transitions to unoccupied valence π ∗(CH 2, CH 3) and σ ∗(C-C) levels. Additional weak features are assigned to Rydberg transitions. The position of the main continuum feature in each spectrum is consistent with the predictions of an empirical relationship with bond length. Systematic variations of spectral intensities are observed which support our assignments. The dominant feature in the K-shell spectrum of ethane, which was previously assigned to C 1 s → 3 p Rydberg transitions, is reassigned to excitation to a 3 p/π ∗(CH 3 ), mixed Rydberg/valence orbital (of antibonding σ- ∗(C-H) character), in comparison to the other alkane spectra. An improved calibration value of 290.74(5) eV for the energy of the C 1 s → π ∗ transition in CO 2 is also obtained.

Analysis of the collision induced far infrared spectrum of ethane

Analysis of observed far i.r. collision-induced absorption in ethane and ethane—rare gas mixtures indicates that only a small fraction is due to the canonical multipole-induced and overlap-induced dipole moments. Nevertheless, multipole-induced dipole spectra calculated with no adjustable parameters are shown to fit the low-frequency wing ( < 60 cm −1) of the observed ethane collision-induced spectrum to within 10%. More than half of the observed intensity in the ethane and ethane—rare gas far i.r. spectra has been shown to be due to rotational and vibrational modulation of dipoles induced by electric fields which do not reflect the full symmetry of the inducing molecule but depend strongly on local symmetry of the inducing charge distribution. The ethane CC stretch, ν 3 at 993 cm −1, has been observed to have a collision-induced absorption which is also assigned to effects of local symmetry. In addition to the non-resonant effects due to overlap and frame distortion, we present a new theoretical analysis of a resonant intermolecular effect, also due to frame distortion, at the frequency of the torsional mode, ν 4.

EOM/Propagator ionization potentials: Effect of an extended operator manifold on the predicted valence‐shell ionization spectra of ethane, ethylene, and acetylene

AbstractThe orthogonalized direct diagonalization (ODD) method is used to predict the valence‐shell ionization spectra for the series of hydrocarbons ethane (C2H6), ethylene (C2H4), and acetylene (C2H2) within an EOM/propagator formalism. Both (a) third‐order and (b) higher‐order (with h5 terms in the excitation operator manifold) calculations are presented in order to illustrate the effect of the extended operator manifold on the predicted valence‐shell spectra. It is shown that the major effect of the h5 manifold is concentrated in its “occupied” part. Along with a general shifting of the main lines for outer valence ionizations to lower values (together with a slight reduction in pole strength), it is found that the effect of the h5 manifold in the inner valence region is dependent on the system being studied.

Direct mass-spectrometric studies of the pyrolysis of carbonaceous fuels: II. Qualitative observations of primary and secondary processes in biomass

Initial, qualitative results for the primary and secondary pyrolysis of biomass and related compounds are shown, using the flame-pyrolysis direct free-jet molecular-beam mass-spectrometric sampling system described in Part I. Time-resolved pyrolysis data are shown for wood. Integrated primary pyrolysis spectra are shown for cellulose, lignin, wood, oil shale, coal, and polyethylene specimens, flash-heated in 1-atm 900°C steam-argon. Our spectra for cellulose and lignin are compared with several reported in the literature using analytical pyrolysis and other techniques. Secondary cracking spectra of ethane, n-butane and cellulose are shown illustrating the ability of this technique to separate primary from secondary processes. Finally, the present technique is compared with more conventional analytical pyrolysis-mass spectrometry approaches.

ChemInform Abstract: EXCITED STATES AND PHOTOCHEMISTRY OF SATURATED MOLECULES. THE VIBRATIONAL STRUCTURE IN THE ELECTRONIC SPECTRUM OF ETHANE

Abstract Ab initio wavefunctions including single excitation CI are used to analyze the origin of the vibrational structure in the low-energy band of the electronic spectrum of ethane. The calculations suggest that the vibrational structure appears to be due to the overlapping progressions from two vertical states (1 E u and 1 A 2 u ), both of which are unstable to distortion to C 2 h symmetry, wherein they are characterized by significantly lengthened CC bonds.

Excited states and photochemistry of saturated molecules. The vibrational structure in the electronic spectrum of ethane

Ab initio wavefunctions including single excitation CI are used to analyze the origin of the vibrational structure in the low-energy band of the electronic spectrum of ethane. The calculations suggest that the vibrational structure appears to be due to the overlapping progressions from two vertical states (1 E u and 1 A 2 u ), both of which are unstable to distortion to C 2 h symmetry, wherein they are characterized by significantly lengthened CC bonds.

Torsional Splittings and Assignments of the Doppler-Limited Spectrum of Ethane in the C-H Stretching Region.

The Doppler-limited absorption spectrum of the C-H stretching region of ethane has been recorded at T≃ 119 K with a tunable difference-frequency laser spectrometer. The strong torsional hot band structure at room temperature is eliminated at 119 K, and the enhanced resolution from the Doppler width reduction allows us to observe small torsional splittings. The two fundamentals in the region, v 7, a perpendicular band and, v 5, a parallel band have been essentially completely assigned as have a large number of transitions in the parallel component of the v 8 + v 11 combination band. A number of perturbations of both global and local nature have been observed. The complete spectrum and a listing of transition wavenumbers, intensities and assignments are presented here to facilitate identification and quantitative analysis of ethane in a variety of monitoring applications. Precise ground state rotational constants have been determined from combination differences.

Auger spectroscopy of polyethylene and poly (ethylene oxide)

The X-ray excited Auger spectra of polyethylene and poly(ethylene oxide) have been corrected for Auger electron energy losses due to interactions with the solid and compared to the corresponding spectra of gas phase molecular analogs. The corrected polyethylene spectrum is an extrapolation of trends observed in the spectra of gas phase alkanes from CH 4 through C 6H 14. The O(KVV) spectrum of poly(ethylene oxide) is similar to that of methyl ether, consistent with similar nearest neighbor environments for the oxygen atoms in the two materials. In contrast, the C(KVV) spectrum of poly(ethylene oxide), a material which contains C-C bonds, is better approximated by the spectrum of ethane (H 3C-CH 3). A comparison of the polyethylene Auger spectrum with the spectra of the normal alkanes and with a self-fold of its X-ray excited valence band photoemission (single hole) spectrum indicates the presence of correlated two-hole final states in the case of polyethylene.

The metal-alkene bond in di-µ-chloro-tetra(ethene)dirhodium(I): direct evidence for the Dewar–Chatt–Duncanson model using X-ray emission and X-ray photoelectron spectroscopies

Changes in carbon-KαX-ray emission spectrum of ethane upon complex formation: together with the alignment of the X-ray photoelectron spectrum of the complex show that ethene both donates charge from the π orbital to rhodium 4d orbitals and also forms bonds in which charge is ‘back-donated’ from the rhodium 4d irbitals to the alkene π* orbital, as predicted by the Dewar–Chatt–Duncanson model.

ChemInform Abstract: AUGER SPECTRA OF ALKANES

The gas‐phase Auger line shapes of the linear alkanes C1 through C6 and of neopentane are presented and analyzed. The general shape of the spectra are characteristic of carbon in a tetrahedral environment with the major feature in all cases occurring at ∼249 eV. The relatively large spectral changes found between methane and ethane results from the direct interaction of the terminal methyl groups in ethane, and the spectra of the higher alkanes are shown to be a composite of contributions from terminal methyl and interior methylene group carbon atoms. Theoretical analysis based on a one‐electron approximation is shown to be capable of making a molecular orbital assignment by comparing calculated vertical transitions to features in the Auger spectra of ethane and propane, and, in the case of ethane, of differentiating between the 2Eg and 2A1g assignment of the ground state of (C2H6)+. A one‐electron based molecular orbital treatment, however, is shown to partially break down in propane and neopentane. Anal...

Auger spectra of alkanes

The gas-phase Auger line shapes of the linear alkanes C1 through C6 and of neopentane are presented and analyzed. The general shape of the spectra are characteristic of carbon in a tetrahedral environment with the major feature in all cases occurring at ∼249 eV. The relatively large spectral changes found between methane and ethane results from the direct interaction of the terminal methyl groups in ethane, and the spectra of the higher alkanes are shown to be a composite of contributions from terminal methyl and interior methylene group carbon atoms. Theoretical analysis based on a one-electron approximation is shown to be capable of making a molecular orbital assignment by comparing calculated vertical transitions to features in the Auger spectra of ethane and propane, and, in the case of ethane, of differentiating between the 2Eg and 2A1g assignment of the ground state of (C2H6)+. A one-electron based molecular orbital treatment, however, is shown to partially break down in propane and neopentane. Analysis of neopentane and the observed absence of any noticeable major peak energy shift with increasing molecular size (as predicted by the one-electron treatment) suggests that some Auger final states occur in which both valence holes are localized on the same subunit of the molecule.

Infrared rotation-vibration spectra of ethane: The parallel band, 2 ν3, of CH 3CD 3

The parallel band, 2 ν 3, of CH 3CD 3 is measured in the region 2715 to 2780 cm −1 under a spectral resolution of ∼0.025 cm −1, increased to ∼0.015 cm −1 by deconvolution. About 460 lines are identified in the 2 ν 3 band, and about 240 lines in a hot band arising from the first excited torsional state. Least-squares analyses with Δ 2 F″ combination differences yield lower-state parameters. An individual subband analysis is undertaken because of perturbations in the vibrational bands studied. Finally, band constants are derived.

ChemInform Abstract: DETAILED FEATURES IN THE LOCAL MODE OVERTONE BANDS OF ETHANE, NEOPENTANE, TETRAMETHYLBUTANE, AND HEXAMETHYLBENZENE

The overtone spectra of ethane in the gas phase at room temperature and neopentane in the liquid phase at 0 °C are measured and analyzed in the region of the pure local mode overtones corresponding to ΔvCH=3, 4, and 5. Overtone spectra are also measured and analyzed for 2, 2, 3, 3‐tetramethylbutane in hexachlorobutadiene solution and for hexamethylbenzene in carbon tetrachloride solution, both at room temperature in the region of ΔvCH=3 and 4. For ethane, neopentane, and tetramethylbutane, the dominant contribution to the overtone band corresponds to a pure CH3 local mode overtone. Combination peaks between different CH3 local oscillators are characterized. Combination peaks are also identified involving a CH3 local oscillator and a low frequency normal mode, with the transitions originating from both the ground vibrational state and a state containing one quantum of the low frequency mode. A computer decomposition of the overtone bands is carried out and a satisfactory fit is achieved in terms of Lorentz...

Detailed features in the local mode overtone bands of ethane, neopentane, tetramethylbutane, and hexamethylbenzene

The overtone spectra of ethane in the gas phase at room temperature and neopentane in the liquid phase at 0 °C are measured and analyzed in the region of the pure local mode overtones corresponding to ΔvCH=3, 4, and 5. Overtone spectra are also measured and analyzed for 2, 2, 3, 3-tetramethylbutane in hexachlorobutadiene solution and for hexamethylbenzene in carbon tetrachloride solution, both at room temperature in the region of ΔvCH=3 and 4. For ethane, neopentane, and tetramethylbutane, the dominant contribution to the overtone band corresponds to a pure CH3 local mode overtone. Combination peaks between different CH3 local oscillators are characterized. Combination peaks are also identified involving a CH3 local oscillator and a low frequency normal mode, with the transitions originating from both the ground vibrational state and a state containing one quantum of the low frequency mode. A computer decomposition of the overtone bands is carried out and a satisfactory fit is achieved in terms of Lorentzian peaks, independently of the degree of vibrational excitation or phase. Narrow bandwidths are observed for the pure local mode overtones of neopentane and the narrow linewidths are attributed to weak intermolecular interactions. Doublet structure in the pure local mode overtones of hexamethylbenzene is attributed to two types of configurationally inequivalent hydrogens.

ChemInform Abstract: ETHANE SPECTRUM BETWEEN 1940 AND 2152 CM‐1: GROUND STATE PARAMETERS

Abstract The absorption spectrum of ethane was recorded between 1940 and 2152 cm−1 at a resolution of 0.025 cm−1. Ground state parameters were determined from the principal band in this region, ν9 + ν12(Eu): B0 = 0.6630353 cm−1, D0J = 1.0406 × 10−6 cm−1, D0JK = 2.575 × 10−6 cm−1 (standard errors are 7, 8, and 13, respectively, in the last digits quoted). The quoted values are from the analyses of 269 ground state combination differences, the standard deviation of the least-squares analysis was 0.0032 cm−1.

Ethane spectrum between 1940 and 2152 cm −1: Ground state parameters

The absorption spectrum of ethane was recorded between 1940 and 2152 cm −1 at a resolution of 0.025 cm −1. Ground state parameters were determined from the principal band in this region, ν 9 + ν 12( E u ): B 0 = 0.6630353 cm −1, D 0 J = 1.0406 × 10 −6 cm −1, D 0 JK = 2.575 × 10 −6 cm −1 (standard errors are 7, 8, and 13, respectively, in the last digits quoted). The quoted values are from the analyses of 269 ground state combination differences, the standard deviation of the least-squares analysis was 0.0032 cm −1.

Raman spectra of ordered crystalline ethane

Abstract The Raman spectrum of ethane in phase II at 74 K has been obtained. The spectrum lends support to the crystal structure previously deducted from i.r. spectra.

Photoelectric absorption spectra of methane (CH 4), methane and hydrogen (H 2) mixtures, and ethane (C 2H 6)

Long path absorption spectra of methane have been recorded photoelectrically from 4200 to 10,600 Å. The region to the red of 6200 Å was studied with column abundances varying from approx. 0.001–1 km-amagat at a resolution of several Å. Ethane spectra in the same region were taken for abundances from about 0.1–1 km-amagat. Short scans at higher resolution and higher methane abundance were obtained for the 6800 Å absorption in the hope of discerning structure due to the presumed 5 v 3 band. The region below 6200 Å was recorded under a few high abundance conditions. It was also scanned with mixtures of methane and hydrogen in an attempt to detect absorption features attributable to simultaneous transitions in H 2 and CH 4. No such bands were detected under the pressures attained. Visual comparison with spectra of Uranus shows that pure methane explains the absorption features of Uranus quite well and that large laboratory amounts are necessary to match the weak absorptions below 6200 Å. A brief description of the complexity of the levels responsible for the methane transitions is given.

Stability and structure of the C2H6+ion: investigation of the photoelectron spectrum of ethane below 14 eV usingab initiomethods

Potential surfaces have been calculated for ethane and the three lowest-lying states of its positive ion using ab initio SCF and CI methods. The C2H6 + states treated consist of two 2 Ag and a single 2 Bg species in the lowest nuclear symmetry considered (C 2h ) and they are found to possess markedly different equilibrium structures both compared to ethane itself and also to one another. The C2H6 + ground state (2 Ag ) is a pure 2 A 1g species (D 3d symmetry) at large CC distances with optimum CCH angles of 100°, but at shorter R CC values it becomes a mixture of both 2 A 1g and 2 Eg character through a large diborane-type (v 12) distortion. The second 2 Ag species is complementary to the first and appears to prefer D 3d symmetry both at large CC values, for which it is a 2 Eg species, and also at short distances, for which it eventually becomes a 2 A 1g state. The 2 Bg species correlates with 2 Eg in D 3d symmetry but is Jahn-Teller distorted, possessing an R CC value of 2·75 bohr and an HCH angle of onl...

Utilization of paramagnetic additives in structural investigations of vinyl ethers of pyridylcarbinols

The PMR spectra of vinyl ethers of pyridylcarbinols are discussed. The unusual paramagnetic shifts in the spectra of these ethers induced by tris(dipivaloylmethanato)europium are analyzed.