Toward the Spectrum of Free Polyethylene:  Linear Alkanes Studied by Carbon 1s Photoelectron Spectroscopy and Theory

Abstract

Trends in carbon 1s ionization energies for the linear alkanes have been investigated using third-generation synchrotron radiation. The study comprises CH(4), C(2)H(6), C(3)H(8), C(4)H(10), C(5)H(12), C(6)H(14), and C(8)H(18). Both inter- and intramolecular shifts in ionization energy have been determined from gas-phase spectra and ab initio calculations. The shifts are decomposed into initial-state and final-state contributions and are shown to relate to the fundamental chemical properties of group electronegativity and polarizability. By extrapolation, we predict C1s spectra of larger n-alkanes, converging toward isolated strands of polyethylene.

Carbon 1s photoelectron spectroscopy of 1-pentyne conformers

“…The calculations used atom-centered Gaussiantype functions contracted to triple-f quality [20] and augmented by polarization functions (TZP) [21], leading to C: [5s, 3p, 1d] and H: [3s, 1p]. For the core-ionized carbon atom, the corresponding nitrogen basis was used with all exponents scaled by a common factor of 0.9293, obtained by minimizing the calculated energy of core-ionized methane [22]. The core of the ionized carbon atom was represented by the effective core potential (ECP) of Stevens et al [23], scaled to account for only one electron in the 1s shell [24].…”

“…To correct for this effect, we have scaled the calculated vibrational energies by a factor of 0.99, except for the C-H stretching mode on the core-ionized carbon atom, which was scaled by 0.95 [22]. The scaling of 0.95 for the core-ionized carbon atom was used for all hybridizations.…”

Semispectroscopic and Quantitative Structure−Property Relationship Estimates of the Equilibrium and Vibrationally Averaged Structure and Dipole Moment of 1-Buten-3-yne

“…Furthermore, on the basis of the computed results, the following qualitative observations were made: 5,6 (i) in alkanes, the methyl group is electron-withdrawing relative to the methylene group, i.e., the methyl group is at the negative end of the molecule; (ii) in alkenes and alkynes, the alkyl group constitutes the positive end of the molecule; and (iii) the ethynyl group is electron-withdrawing relative to the vinyl group. It is worth mentioning that recent measurements by photoelectron spectroscopy 13 provided further evidence for the validity of (i) and (ii). For molecules with conjugate CdC double and CtC triple bonds, e.g., 1-buten-3-yne, 1-penten-3-yne, cis-3-penten-1-yne, trans-3-penten-1-yne, and 2-methyl-1-buten-3-yne, the B3LYP dipole moments were closer to the experimental ones than the HF dipole moments.…”

Accurate calculation of C1s core electron binding energies of some carbon hydrates and substituted benzenes

“…Recently, accurately observed values of adiabatic and vertical C1s ionization energies of alkanes [16], alkenes [17], alkynes [18], fluorobenzenes [19], methylbenzenes [20], and fluoromethylbenzenes [21] have been published. All the experimental values were measured using new generation synchrotorons.…”

“…Adiabatic ionization energies are directly available from a fitting procedure, whereas vertical ionization energies are obtained as centers of gravity of vibrational profiles. The vertical ionization energies are associated with larger uncertainties than adiabatic ionization energies [16]. The object of the present work is to search for a theoret- Table 1 Calculated and observed adiabatic and vertical C1s core electron binding energies, in eV, of some alkanes and alkenes without (C rel = 0 eV) and with (C rel = 0.05 eV) relativistic correction.…”