Effect of Substituent Groups on the Ionization Potentials of Benzenes

Crable, George F.; Kearns, G. L.

doi:10.1021/j100809a014

Cited by 119 publications

(36 citation statements)

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“…The appearance potentials of C6H4X + ions are more than 12 eV, which are much higher than the photon energy of 10.2 eV used in the present study. [26][27][28][29][30][31][32][33][34] Thus, fragmentation-free measurements of the mass spectra for chlorobenzene derivatives are expected in the SPI at 10.2 eV. Figure 2 shows the mass spectra of chlorobenzene, o-dichlorobenzene, and o-chlorophenol obtained by the SPI at 10.2 eV.…”

Section: Resultsmentioning

confidence: 99%

Detection of Chlorobenzene Derivatives Using Vacuum Ultraviolet Ionization Time-of-Flight Mass Spectrometry

2003

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Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied for the detection of chlorobenzene, o-dichlorobenzene, and o-chlorophenol as surrogates for polychlorinated dibenzo-pdioxine/furans (PCDD/F). The photoionization mass spectra of these compounds appear to be fragmentation free in the ionization processes by the VUV-SPI at 10.2 eV (121.6 nm). Quantum chemical calculations support no fragmentation in the photoionization of chlorobenzene derivatives at around 10 eV. The absolute photoionization cross-sections of chlorobenzene, o-dichlorobenzene, and o-chlorophenol were estimated at 10.2 eV. The photoionization cross-section is an important parameter in the detection of chlorobenzene derivatives by the single-photon ionization technique. The detection limit for chlorobenzene is on the order of tenth parts-per-billion volume (ppbv) in the present experimental setup.

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Section: Resultsmentioning

confidence: 99%

Detection of Chlorobenzene Derivatives Using Vacuum Ultraviolet Ionization Time-of-Flight Mass Spectrometry

2003

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“…The nitro compounds gave poor ionization efficiencies in both direct APPI and APLI: in direct APPI only four out of nine of the nitro compounds were ionized, in direct APLI none. Aromatic nitro substituents are strongly electron-withdrawing, which increases the IE of the compound compared with a non-substituted compound [28]. The known IEs for the compounds in this group are in the range of 9.10-10.71 eV, being much higher than the IEs for corresponding compounds in other groups.…”

Section: Nitro Compoundsmentioning

confidence: 88%

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Kauppila

Kersten

Benter

2015

J. Am. Soc. Mass Spectrom.

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Abstract. Seventy-seven EPA priority environmental pollutants were analyzed using gas chromatography-mass spectrometry (GC-MS) equipped with an optimized atmospheric pressure photoionization (APPI) and an atmospheric pressure laser ionization (APLI) interface with and without dopants. The analyzed compounds included e.g., polycyclic aromatic hydrocarbons (PAHs), nitro compounds, halogenated compounds, aromatic compounds with phenolic, acidic, alcohol, and amino groups, phthalate and adipatic esters, and aliphatic ethers. Toluene, anisole, chlorobenzene, and acetone were tested as dopants. The widest range of analytes was ionized using direct APPI (66/77 compounds). The introduction of dopants decreased the amount of compounds ionized in APPI (e.g., 54/77 with toluene), but in many cases the ionization efficiency increased. While in direct APPI the formation of molecular ions via photoionization was the main ionization reaction, dopant-assisted (DA) APPI promoted ionization reactions, such as charge exchange and proton transfer. Direct APLI ionized a much smaller amount of compounds than APPI (41/77 compounds), showing selectivity towards compounds with low ionization energies (IEs) and long-lived resonantly excited intermediate states. DA-APLI, however, was able to ionize a higher amount of compounds (e.g. 51/77 with toluene), as the ionization took place entirely through dopant-assisted ion/molecule reactions similar to those in DA-APPI. Best ionization efficiency in APPI and APLI (both direct and DA) was obtained for PAHs and aromatics with O-and N-functionalities, whereas nitro compounds and aliphatic ethers were the most difficult to ionize. Halogenated aromatics and esters were (mainly) ionized in APPI, but not in APLI.

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“…As expected, there is a clear inverse relationship between the binding energy and number of electrons produced; that is, more secondary electrons were generated for lower binding energies. For reference, the ionization energies of the carbon and oxygen 2p orbitals and the experimentallydetermined molecular ionization energies for phenol, benzene, and ethyl acetate are also shown in the figure [38,39]. This modeling study predicts that the total number of electrons generated from an absorbed EUV photon would be 2 to 2.3 for the realistic range of ionization energies (8.5-10 eV), which is in general agreement with the electron map approach starting with actual atomic ionization energies of the commercial resist (1.8 ± 1.0 total electrons).…”

Section: Secondary Electron Output Dependence On Molecular Binding Enmentioning

confidence: 99%

Secondary Electrons in EUV Lithography

Torok

Herbol

et al. 2013

J. Photopol. Sci. Technol.

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Secondary electrons play critical roles in several imaging technologies, including extreme ultraviolet (EUV) lithography. At longer wavelengths of light (e.g. 193 and 248 nm), the photons are directly involved in the photochemistry occurring during photolysis. EUV light (13.5 nm, 92 eV), however, first creates a photoelectron, and this electron, or its subsequent daughter electrons create most of the chemical changes that occur during exposure. Despite the importance of these electrons, the details surrounding the chemical events leading to acid production remain poorly understood. Previously reported experimental results using high PAG-loaded resists have demonstrated that up to five or six photoacids can be generated per incident photon. Until recently, only electron recombination events were thought to play a role in acid generation, requiring that at least as many secondary electrons are produced to yield a given number of acid molecules. However, the initial results we have obtained using a Monte Carlo-based modeling program, LESiS, demonstrate that only two to three secondary electrons are made per absorbed EUV photon. A more comprehensive understanding of EUVinduced acid generation is therefore needed for the development of higher performance resists.

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Effect of Substituent Groups on the Ionization Potentials of Benzenes

Cited by 119 publications

References 0 publications

Detection of Chlorobenzene Derivatives Using Vacuum Ultraviolet Ionization Time-of-Flight Mass Spectrometry

Detection of Chlorobenzene Derivatives Using Vacuum Ultraviolet Ionization Time-of-Flight Mass Spectrometry

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Secondary Electrons in EUV Lithography

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