A comparison of the absorption spectra of the fluorobenzenes and benzene in the region 4.5-9.5 eV

Philis, John G.; Bolovinos, A.; Andritsopoulos, G.; Pantos, E.; Tsekeris, P.

doi:10.1088/0022-3700/14/19/013

Cited by 90 publications

(84 citation statements)

References 53 publications

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“…The high-quality fits we achieved are illustrated in Fig. 3, while the so-determined OOSs are listed in Table III along with the results from previous experimental [24][25][26][27][28] and theoretical [36][37][38][39][40][41] investigations. Note that we estimate the uncertainty, again at the one standard deviation level, on our OOSs to be ∼20%.…”

Section: Resultsmentioning

confidence: 92%

“…21 Burrow et al 22 determined the vertical electron affinities and characterized the temporary anion states of a series of hydrocarbons including benzene, using electron transmission spectroscopy, while a review of all these resonance studies was provided by Allan. 23 Most experimental studies into excitation of the 1 B 1u and 1 E 1u electronic states have employed either photoabsorption or dipole (e,e ) techniques, [24][25][26][27][28] in order to determine their respective optical oscillator strengths (OOSs). Agreement between the various OOS measurements for the 1 E 1u state is typically very good to the ±5% level, however, for the 1 B 1u state there is a serious disagreement between the results of Feng et al 24 , and Suto et al 25 on the one hand, and those of Philis et al, 26 Pantos et al 27 and Hammond and Price, 28 on the other.…”

Section: Introductionmentioning

confidence: 99%

“…23 Most experimental studies into excitation of the 1 B 1u and 1 E 1u electronic states have employed either photoabsorption or dipole (e,e ) techniques, [24][25][26][27][28] in order to determine their respective optical oscillator strengths (OOSs). Agreement between the various OOS measurements for the 1 E 1u state is typically very good to the ±5% level, however, for the 1 B 1u state there is a serious disagreement between the results of Feng et al 24 , and Suto et al 25 on the one hand, and those of Philis et al, 26 Pantos et al 27 and Hammond and Price, 28 on the other. Finally, we note the total ionization cross section results from measurements due to Schram et al 29 From a theoretical perspective, elastic electron scattering from C 6 H 6 , at energies up to about 40 eV, using single-center expansion methods at the static exchange level, were reported by Gianturco and Lucchese.…”

Section: Introductionmentioning

confidence: 99%

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A study of electron scattering from benzene: Excitation of the 1B1u, 3E2g, and 1E1u electronic states

Kato

Hoshino

Tanaka

et al. 2011

The Journal of Chemical Physics

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We report results from measurements for differential and integral cross sections of the unresolved 1B1u and 3E2g electronic states and the 1E1u electronic state in benzene. The energy range of this work was 10–200 eV, while the angular range of the differential cross sections was ∼3°–130°. To the best of our knowledge there are no other corresponding theoretical or experimental data against which we can compare the present results. A generalized oscillator strength analysis was applied to our 100 and 200 eV differential cross section data, for both the 1B1u and 1E1u states, with optical oscillator strengths being derived in each case. The respective optical oscillator strengths were found to be consistent with many, but not all, of the earlier theoretical and experimental determinations. Finally, we present theoretical integral cross sections for both the 1B1u and 1E1u electronic states, as calculated within the BEf-scaling formalism, and compare them against relevant results from our measurements. From that comparison, an integral cross section for the optically forbidden 3E2g state is also derived.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A study of electron scattering from benzene: Excitation of the 1B1u, 3E2g, and 1E1u electronic states

Kato

Hoshino

Tanaka

et al. 2011

The Journal of Chemical Physics

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“…47 These differences suggest that the nature of the lowest excited singlet state may be different for the two classes of the compounds, despite the previous ππ* assignment of S 1 for all fluorinated benzenes. 42,44 More specifically, it is possible that the 1 πσ* state, which is formed by the promotion of an electron from the ring-centered π orbital to the σ* orbital, localized on the C-F bond, could be the emitting state in molecules with high degrees of fluorination (i.e., n ) 5, 6). Figure 12 presents the TDDFT vertical excitation energies for the lowest-energy 1 ππ* and 1 πσ* states at optimized ground-state geometry.…”

Section: Fluorinated Benzenesmentioning

confidence: 99%

Role of the πσ* State in Molecular Photophysics

2010

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P hotosynthesis, which depends on light-driven energy and electron transfer in assemblies of porphyrins, chlorophylls, and carotenoids, is just one example of the many complex natural systems of photobiology. A fuller understanding of the spectroscopy and photophysics of simple aromatic molecules is central to elucidating photochemical processes in the more sophisticated assemblies of photobiology. Moreover, developing a better grasp of the photophysics of simple aromatic molecules will also enhance our ability to create and improve practical applications in photochemical energy conversion, molecular nanophotonics, and molecular electronics. In this Account, we present a concerted experimental and theoretical study of aromatic ethynes, aromatic nitriles, and fluorinated benzenes, illustrating the important roles that the low-lying πσ* state plays in the electronic relaxation of these aromatic compounds.Diphenylacetylene, 4-dialkylaminobenzonitriles, 4-dialkylaminobenzethynes, and fluorinated benzenes exhibit fluorescence that strongly quenches as the excitation energy is increased for gas-phase systems and at elevated temperatures in solution. Much of this interesting photophysical behavior can be attributed to the presence of a dark intermediate state that crosses the fluorescent ππ* state. Our quantum chemistry calculations, as well as time-resolved laser spectroscopies, indicate that this dark intermediate state is the πσ* state that arises from the promotion of an electron from the π orbital of the phenyl ring to the σ* orbital localized in the CtX group (where X is CH and N) or on the CsX group (where X is a halogen). These crossings not only lead to the strong excitation energy and temperature dependence of fluorescence but also induce highly interesting πσ*-mediated intramolecular charge transfer in 4-dialkylaminobenzonitriles.Most previous studies on the excited-state dynamics of organic molecules have examined aromatic hydrocarbons, nitrogen heterocycles, aromatic carbonyl compounds, and polyenes, which have low-lying excited states of ππ* character (hydrocarbons and polyenes) or nπ* and ππ* character (carbonyls and N-heterocycles). These studies have revealed important involvement of selection rules (promoting vibrational modes and spin-orbit coupling) and Franck-Condon factors for radiationless transitions, which have important effects on photophysical properties. The recent experimental and time-dependent density functional theory (TDDFT) calculations of aromatic ethynes, nitriles, and perfluorinated benzenes described in this Account demonstrate the importance of the bound excited state of a πσ* configuration in these molecules.

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“…This excited state is the 1 pp* (1 1 B 2 ) state which has been well-documented in the halobenzenes through nanosecond UV (1+1) REMPI experiments around 266 nm. [22][23][24] The monohalobenzenes all follow (m+n) REMPI patterns. At the highest intensities used, the parent ion yields of all five species rapidly decrease as other processes become dominant, such as multiple ionization and fragmentation.…”

Section: Introductionmentioning

confidence: 98%

Ultrafast REMPI in benzene and the monohalobenzenes without the focal volume effect

Scarborough

Strohaber

Foote

et al. 2011

Phys. Chem. Chem. Phys.

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We report on the photoionization and photofragmentation of benzene (C 6 H 6 ) and of the monohalobenzenes C 6 H 5 -X (X = F, Cl, Br, I) under intense-field, single-molecule conditions. We focus 50-fs, 804-nm pulses from a Ti:sapphire laser source, and record ion mass spectra as a function of intensity in the range B10 13 W/cm 2 to B10 15 W/cm 2 . We count ions that were created in the central, most intense part of the focal area; ions from other regions are rejected. For all targets, stable parent ions (C 6 H 5 X + ) are observed. Our data is consistent with resonance-enhanced multiphoton ionization (REMPI) involving the neutral 1 pp* excited state (primarily a phenyl excitation): all of our plots of parent ion yield versus intensity display a kink when this excitation saturates. From the intensity dependence of the ion yield we infer that both the HOMO and the HOMOÀ1 contribute to ionization in C 6 H 5 F and C 6 H 5 Cl. The proportion of phenyl (C 6 H 5 ) fragments in the mass spectra increases in the order X = F, Cl, Br, I. We ascribe these substituent-dependent observations to the different lifetimes of the C 6 H 5 X 1 pp* states. In X = I the heavy-atom effect leads to ultrafast intersystem crossing to a dissociative 3 ns* state. This breaks the C-I bond in an early stage of the ultrashort pulse, which explains the abundance of fragments that we find in the iodobenzene mass spectrum. For the lighter X = F, Cl, and Br this dissociation is much slower, which explains the lesser degree of fragmentation observed for these three molecules.

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A comparison of the absorption spectra of the fluorobenzenes and benzene in the region 4.5-9.5 eV

Cited by 90 publications

References 53 publications

A study of electron scattering from benzene: Excitation of the 1B1u, 3E2g, and 1E1u electronic states

A study of electron scattering from benzene: Excitation of the 1B1u, 3E2g, and 1E1u electronic states

Role of the πσ* State in Molecular Photophysics

Ultrafast REMPI in benzene and the monohalobenzenes without the focal volume effect

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