Ionization Potential Of Benzene Research Articles

Ab Initio second-order perturbation calculations for excited and ionized states of benzene isomers

The lower excitation energies and ionization potentials of benzene and its conjugated planar isomers have been computed by a second-order perturbation method using the SCF-MOS obtained from a minimal atomic basis set. The calculations include all the singly and doubly excited configurations with respect to the initial and final states. The predictions of the SCF one-electron model are greatly improved by this treatment where both the rearrangement of the electron cloud and the change in correlation energy are taken into account. The deviations from experiment data are reduced to 1 eV or less.

Photodissociation spectroscopy of (benzene–toluene)+. Charge delocalization in the hetero-dimer ion

The electronic spectrum of the benzene–toluene hetero-dimer ion is measured in the 380–1400 nm region. The spectrum shows intense bands around 1175 and 670 nm and a weaker band around 920 nm, which correspond to charge resonance (CR) bands of homo-dimer ions. The observation indicates that the positive charge stays on the benzene part in some probability, although the ionization potential of benzene is 0.4162 eV higher than that of toluene. A local excitation (LE) band is observed around 420 nm, where a π←π transition is locally excited in the charged benzene or toluene molecule. On the basis of the positions of the CR-like bands, as well as the intensity of the LE band relative to that of homo-dimer ions, the probability of finding the charge on the benzene molecule is analyzed to be approximately 36%.

Charge Delocalization in Benzene−Naphthalene Hetero-Dimer Cation

The electronic spectrum of the benzene−naphthalene hetero-dimer cation is measured in the 400−1200 nm region by photodissociation spectroscopy. The most intense band at 580 nm is assigned to a local excitation (LE) band of the naphthalene cation chromophore. In addition to this band, an LE band of the benzene cation chromophore of the hetero-dimer is observed at nearly the same position (430 nm) as that of the benzene homo-dimer cation. The observation indicates that the positive charge stays on the benzene molecule in some probability, although the ionization potential of benzene is by 1.10 eV higher than that of naphthalene. The spectrum of the hetero-dimer cation also shows an intermolecular charge transfer (CT) band around 920 nm. On the basis of the position of the CT band as well as the intensity of the LE band relative to that of the homo-dimer, the probability of finding the charge on the benzene molecule is analyzed to be approximately 9%.

Two-color 2 + 2 photon resonance-enhanced ionization of benzene-carbon tetrachloride binary clusters

Binary clusters produced from benzene—carbon tetrachloride (9:1) mixtures are ionized by two-color (UV-VIS) excitation through the resonance pumping of the benzene S 2 state or the charge-transfer state of the benzene—carbon tetrachloride complex. The observed ions are C 6H + 7, (C 6H 6) n C 6H 6Cl +, C 7H 5H 7Cl +, and C 7H 5Cl + 2 in addition to (C 6H 6) + n ( n = 1,2,3,..). Resonance two-photon excitation at 210 nm, in which the total energy (11.8 eV) is greater than the ionization potential of benzene (9.25 eV), generates neutral intermediate states with lifetimes of 250–320 ns. The visible laser ionization with a delay from the first two-photon excitation appeared to be also a two-photon resonance process, the first step of which is probably the T ← T transition of benzene. The main reason for maintaining neutral states, in spite of the absorption of high energy, is attributed to the double excitation of C 6H 6 and CCl 4 molecules and the subsequent dissociation of electronically excited CCl 4 in the binary clusters. Condensation reactions of the component molecules in a benzene dimer ion unit and in benzene—carbon tetrachloride binary ions are found to be highly efficient for this system.

A precise determination of the first ionization potential of benzene

The first ionization potentials of benzene and benzene- d 6 have been precisely determined by the extrapolation of three-photon resonant Rydberg states in the four-photon ionization spectrum of the jet-cooled molecule. The convergence of resolved transitions in two Rydberg series for principal quantum numbers as high as 14 (- h 6) and 15 (- d 6) establish adiabatic thtesholds of 74573.0 ± 2.0 cm −1, and 74592.5 = ± 1.2 cm −1, respectively. These results are crucial for the understanding of the many excited states of benzene in terms of quantum defect theory. Precise quantum defects have been obtained for several Rydberg series and their variation with principal quantum number is reported. The results strongly suggest that the R‴ series of Wilkinson is derived from aπ(e 1g)→ nf±1 Rydberg excitation.

ChemInform Abstract: APPLICATION OF Xα MULTIPLE‐SCATTERING THEORY TO PLANAR ORGANIC MOLECULES: ONE‐ELECTRON PROPERTIES AND IONIZATION POTENTIALS OF BENZENE, PYRIDINE PYRAZINE, PYRROLE, AND IMIDAZOLE

Chemischer InformationsdienstVolume 12, Issue 2 Physical Organic Chemistry ChemInform Abstract: APPLICATION OF Xα MULTIPLE-SCATTERING THEORY TO PLANAR ORGANIC MOLECULES: ONE-ELECTRON PROPERTIES AND IONIZATION POTENTIALS OF BENZENE, PYRIDINE PYRAZINE, PYRROLE, AND IMIDAZOLE D. A. CASE, D. A. CASESearch for more papers by this authorM. COOK, M. COOKSearch for more papers by this authorM. KARPLUS, M. KARPLUSSearch for more papers by this author D. A. CASE, D. A. CASESearch for more papers by this authorM. COOK, M. COOKSearch for more papers by this authorM. KARPLUS, M. KARPLUSSearch for more papers by this author First published: January 13, 1981 https://doi.org/10.1002/chin.198102068AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue2January 13, 1981 RelatedInformation

Application of Xα multiple-scattering theory to planar organic molecules: One-electron properties and ionization potentials of benzene, pyridine, pyrazine, pyrrole, and imidazole

Xα multiple scattering wave functions and molecular properties are reported for benzene, pyridine, pyrazine, pyrrole, and imidazole. The calculations demonstrate that useful results can be obtained for planar conjugated organic molecules with the Xα method. Values are obtained for ionization potentials and one electron properties, including dipole and quadrupole moments, diamagnetic susceptibilities and nuclear quadrupole coupling constants. In general the results are in better agreement with experiment than minimum basis set Hartree–Fock calculations; this generalization is not true for molecular properties that are dominated by hydrogen atoms, such as deuteron quadrupole coupling constants. The sensitivity of the results to changes in sphere overlap is studied in detail for pyridine and it is found that useful accuracy can be achieved over a fairly broad range of overlap parameters. Calculated ionization potentials agree well with recent assignments of the photoelectron spectra, except for the relative ordering of π and nitrogen lone-pair orbitals. This difference is analysed in terms of correlation effects in lone-pair ionizations. As part of the comparisons, detailed tabulations of one-electron properties and ionization potentials obtained from experiments and other calculations are provided.

Line shapes of charge-transfer spectra

The theoretical description of condensed-media line shapes of electronic transitions, as developed in earlier papers, is applied to the charge-transfer (CT) spectra of the complexes mesitylene:tetracyanoethylene (Mes:TCNE) and anthracene:chloranil (AN:CA). Results are compared with those previously published for benzene:iodine (Bz:I2), and the factors which contribute to line broadening (inhomogeneous broadening, the Franck–Condon profile, and donor–acceptor vibrational motion) are discussed. The results of an attempt to determine the contributions to the line shape made by intermolecular orbital couplings are presented. In addition, the Bz:I2 CT spectrum is reinvestigated, and the question of which ionization potential of benzene is involved is addressed.

A mechanism for hydrogen scrambling in ionized benzene

By SCF molecular orbital calculations, it has been shown that hydrogen atom scrambling for ionized benzene can occur via a simple movement of one proton to an adjacent carbon. The cyclic intermediate ion has an energy of 1.86 eV above the ionization potential of benzene, which is lower than the energy necessary for fragmentation or for ring opening.

The electronic structure of molecules by a many-body approach. I. Ionization potentials and one-electron properties of benzene

The ionization potentials of benzene are studied by an ab initio many-body approach which includes the effects of electron correlation and reorganization beyond the one-particle approximation. The calculations confirm the assignment of the photoelectron spectrum experimentally proposed by Jonsson and Lindholm: 1e1g(π), 2e2g, 1a2u(π), 2e1u, 1b2u, 1b1u, 2a1g, 1e2g in order of increasing binding energy. To definitely establish the ordering of the ionization potentials in the second band, which has been very controversial, the corresponding vibrational structure has been calculated. A number of one-electron properties are calculated in the one-particle approximation and compared to experimental work and other theoretical calculations.

Ionization Potentials of Benzene, Hexadeuterobenzene, and Pyridine from Their Observed Rydberg Series in the Region 600–2000 A

Ionization Potentials of Benzene, Hexadeuterobenzene, and Pyridine from Their Observed Rydberg Series in the Region 600–2000 A

Calculation of the Absorption Spectrum of Wurster's Salts

The so-called Wurster's salts, radicals which occur in the oxidation of the paraphenylene diamines, show a strong absorption in the visible. The frequency and the intensity were calculated by the method of completely antisymmetrized products of molecular orbitals, with the introduction of but one empirical constant, namely, the difference between the ionization potential of the non-bonding nitrogen electron in ammonia, and the ionization potential of benzene. The results are in good agreement with the observed absorption band. The calculated intensity corresponds to an electron number of about 0.3, the observed one to about 0.1. The shift of the band to longer wave-length, and the intensification upon substitution of C${\mathrm{H}}_{3}$ groups on the nitrogen is explained qualitatively.

The Dissociation of Benzene (C6H6), Pyridine (C5H5N) and Cyclohexane (C6H12) by Electron Impact

The dissociation of ${\mathrm{C}}_{6}$${\mathrm{H}}_{6}$, ${\mathrm{C}}_{5}$${\mathrm{H}}_{5}$N, and ${\mathrm{C}}_{6}$${\mathrm{H}}_{12}$ by electron impact has been investigated with a mass spectrograph. Four doubly charged and thirty-one singly charged positive ions were observed in the dissociation of benzene. The relative abundance, for electrons of 72 volts energy, and the appearance potential are given for each ion. The first and second ionization potentials of benzene are 9.8\ifmmode\pm\else\textpm\fi{}0.1 and 17.2\ifmmode\pm\else\textpm\fi{}1.0 volts, respectively. The ionization potential of ${\mathrm{C}}_{5}$${\mathrm{H}}_{5}$N is 9.8\ifmmode\pm\else\textpm\fi{}0.2 volt and of ${\mathrm{C}}_{6}$${\mathrm{H}}_{12}$, 11.0\ifmmode\pm\else\textpm\fi{}0.2 volt. In each of the three vapors, certain of the ions resulting from the dissociation process have a doublet character. The components have a constant energy separation independent of magnetic field. The components also have different appearance potentials. The interpretation given is that these particular ions are formed by two different processes, one of which imparts a definite amount of kinetic energy to the ion.

The Far Ultraviolet Absorption Spectra and Ionization Potentials of C6H6 and C6D6

The absorption spectra of C6H6 and C6D6 have been photographed under high dispersion in the region 2000–1000A. The spectra of both substances are very similar. A strong continuous absorption starts fairly sharply around 1840A and gradually weakens out to zero at 1600A. It is followed by a region extending down to about 1360A which contains very strong sharp bands. The strongest of these bands only suffer small shifts to the violet in going from C6H6 to C6D6. This shift which is due to the change in the difference of zero-point energy between the normal and the excited states reveals the bands to be vibrationless electronic transitions. It was found that these bands could be arranged into two Rydberg series which had approximately the same limit corresponding to an ionization potential of 9.190±.005 volts for C6H6. The ionization potential of C6D6 is only about 3 × 10—4 volts greater than that for C6H6. All the electronic states are split up into patterns which are believed to be caused by true electronic multiplicity. The excitation is apparently from a nonbonding electron more strongly attached to the carbon atom. The vibrations which accompany the bands are comparatively weak. However for C6H6 the following vibration frequencies associated with the excited states were observed. ω1 = 677 cm—1, ω2 = 968 cm—1. These become 630 and 926 cm—1 for C6D6. Tentative assignments of their modes of vibration are made. The bands below 1360A are considerably more diffuse than those previously mentioned and the isotopic shifts to the violet are much larger for these bands. However they are still believed to be vibrationless electronic transitions though they are due to the excitation of an electron which is considerably more bonding than that corresponding to the first ionization potential. A consideration of them enables the approximate value 11.7±.3 volts to be predicted for the second ionization potential of benzene.