On-line resonance-enhanced multiphoton ionization time-of-flight laser mass spectrometry for combined multi-component-pattern analysis and target-compound monitoring: non-chlorinated aromatics and chlorobenzene in flue gases of combustion processes

Heger, Hans Jörg; Boesl, U.; Zimmermann, Ralf; Dorfner, Ralph; Kettrup, A.

doi:10.1255/ejms.249

Cited by 17 publications

(8 citation statements)

References 24 publications

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“…The electronic spectroscopy of the chlorobenzene monomer is well known and has been extensively studied previously by other groups using both R2PI and laser induced fluorescence spectroscopy. 70,[95][96][97][98] Note also that the size range of clusters that we observe is similar to that found in the prior ultrafast experiments, where a similar source was used. 58 From Figure 2, it is apparent that the clusters uniformly exhibit much broader absorption features than the monomer, yet the spectra of different clusters in the range n = 2-4 are similar.…”

Section: Resultssupporting

confidence: 82%

On π-stacking, C-H/π, and halogen bonding interactions in halobenzene clusters: Resonant two-photon ionization studies of chlorobenzene

Muzangwa

Nyambo

Uhler

et al. 2012

The Journal of Chemical Physics

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Noncovalent interactions such as hydrogen bonding, π-π stacking, CH/π interactions, and halogen bonding play crucial roles in a broad spectrum of chemical and biochemical processes, and can exist in cooperation or competition. Here we report studies of the homoclusters of chlorobenzene, a prototypical system where π-π stacking, CH/π interactions, and halogen bonding interactions may all be present. The electronic spectra of chlorobenzene monomer and clusters (Clbz)(n) with n = 1-4 were obtained using resonant 2-photon ionization in the origin region of the S(0)-S(1) (ππ*) state of the monomer. The cluster spectra show in all cases a broad spectrum whose center is redshifted from the monomer absorption. Electronic structure calculations aid in showing that the spectral broadening arises in large part from inhomogeneous sources, including the presence of multiple isomers and Franck-Condon (FC) activity associated with geometrical changes induced by electronic excitation. Calculations at the M06-2x/aug-cc-pVDZ level find in total five minimum energy structures for the dimer, four π-stacked structures, and one T-shaped, and six representative minimum energy structures were found for the trimer. The calculated time-dependent density functional theory spectra using range-separated and meta-GGA hybrid functionals show that these isomers absorb over a range that is roughly consistent with the breadth of the experimental spectra, and the calculated absorptions are redshifted with respect to the monomer transition, in agreement with experiment. Due to the significant geometry change in the electronic transition, where for the dimer a transition from a parallel displaced to sandwich structure occurs with a reduced separation of the two monomers, significant FC activity is predicted in low frequency intermolecular modes.

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Section: Resultssupporting

confidence: 82%

On π-stacking, C-H/π, and halogen bonding interactions in halobenzene clusters: Resonant two-photon ionization studies of chlorobenzene

Muzangwa

Nyambo

Uhler

et al. 2012

The Journal of Chemical Physics

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“…Representative R2PI spectra of the bromobenzene monomer, dimer, and trimer in the region of the origin band of the monomer S 0 –S 1 (ππ*) transition are displayed in Figure . Note that the electronic spectroscopy of the monomer has previously been studied. ,− Focusing on the region of the origin band, the spectra for the clusters show a broad absorption which peaks to lower energy as compared to the monomer. This finding is similar to that observed for chlorobenzene and related systems, including toluene and fluorobenzene. ,,, Based upon the previous work, we attribute this broadness primarily to the presence of different isomers and unresolved vibrational structure in Franck–Condon active modes.…”

Section: Resultsmentioning

confidence: 99%

π-Stacking, C–H/π, and Halogen Bonding Interactions in Bromobenzene and Mixed Bromobenzene–Benzene Clusters

et al. 2013

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Noncovalent interactions play an important role in many chemical and biochemical processes. Building upon our recent study of the homoclusters of chlorobenzene, where π-π stacking and CH/π interactions were identified as the most important binding motifs, in this work we present a study of bromobenzene (PhBr) and mixed bromobenzene-benzene clusters. Electronic spectra in the region of the PhBr monomer S0-S1 (ππ*) transition were obtained using resonant two-photon ionization (R2PI) methods combined with time-of-flight mass analysis. As previously found for related systems, the PhBr cluster spectra show a broad feature whose center is red-shifted from the monomer absorption, and electronic structure calculations indicate the presence of multiple isomers and Franck-Condon activity in low-frequency intermolecular modes. Calculations at the M06-2X/aug-cc-pVDZ level find in total eight minimum energy structures for the PhBr dimer: four π-stacked structures differing in the relative orientation of the Br atoms (denoted D1-D4), one T-shaped structure (D5), and three halogen bonded structures (D6-D8). The calculated binding energies of these complexes, corrected for basis set superposition error (BSSE) and zero-point energy (ZPE), are in the range of -6 to -24 kJ/mol. Time-dependent density functional theory (TDDFT) calculations predict that these isomers absorb over a range that is roughly consistent with the breadth of the experimental spectrum. To examine the influence of dipole-dipole interaction, R2PI spectra were also obtained for the mixed PhBr···benzene dimer, where the spectral congestion is reduced and clear vibrational structure is observed. This structure is well-simulated by Franck-Condon calculations that incorporate the lowest frequency intermolecular modes. Calculations find four minimum energy structures for the mixed dimer and predict that the binding energy of the global minimum is reduced by ~30% relative to the global minimum PhBr dimer structure.

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“…Furthermore, in many cases, REMPI is a soft ionization technique that can be adjusted to be nearly fragmentation-free. Because of these properties, the combination of REMPI with mass spectrometric analysis of the formed ions has an outstanding position for on-line analyzing of traces of aromatic compounds in complex gas mixtures. ,− Recently, the application of mobile REMPI-TOFMS instruments for on-line monitoring of PAH and other aromatic species in the flue gas of industrial incineration plants has been reported. − This includes the on-line measurement of monochlorobenzene, , which has been identified as a surrogate for the dioxin emission of waste incineration plants. Further applications for monitoring flavor-active compounds in the off-gas of the coffee-roasting process have been reported …”

mentioning

confidence: 99%

A Mobile Mass Spectrometer for Comprehensive On-Line Analysis of Trace and Bulk Components of Complex Gas Mixtures: Parallel Application of the Laser-Based Ionization Methods VUV Single- Photon Ionization, Resonant Multiphoton Ioniza- tion, and Laser-Induced Electron Impact Ionization

2001

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A newly developed compact and mobile time-of-flight mass spectrometer (TOFMS) for on-line analysis and monitoring of complex gas mixtures is presented. The instrument is designed for a (quasi-)simultaneous application of three ionization techniques that exhibit different ionization selectivities. The highly selective resonance-enhanced multiphoton ionization (REMPI) technique, using 266-nm UV laser pulses, is applied for selective and fragmentationless ionization of aromatic compounds at trace levels (parts-per-billion volume range). Mass spectra obtained using this technique show the chemical signature solely of monocyclic (benzene, phenols, etc.) and polycyclic (naphthalene, phenathrene, indol, etc.) aromatic species. Furthermore, the less selective but still fragmentationless single photon ionization (SPI) technique with 118-nm VUV laser pulses allows the ionization of compounds with an ionization potential below 10.5 eV. Mass spectra obtained using this technique show the profile of most organic compounds (aliphatic and aromatic species, like nonane, acetaldehyde, or pyrrol) and some inorganic compounds (e.g., ammonia, nitrogen monoxide). Finally, the nonselective ionization technique laser-induced electron-impact ionization (LEI) is applied. However, the sensitivity of the LEI technique is adjusted to be fairly low. Thus, the LEI signal in the mass spectra gives information on the inorganic bulk constituents of the sample (i.e., compounds such as water, oxygen, nitrogen, and carbon dioxide). Because the three ionization methods (REMPI, SPI, LEI) exhibit largely different ionization selectivities, the isolated application of each method alone solely provides specific mass spectrometric information about the sample composition. Special techniques have been developed and applied which allow the quasi-parallel use of all three ionization techniques for on-line monitoring purposes. Thus, a comprehensive characterization of complex samples is feasible jointly using the characteristic advantages of the three ionization techniques. Laboratory applications show results on rapid overview characterization of mineral oil-based fuels and coffee headspace. The first reported field applications include timely resolved on-line monitoring results on automobile exhausts and of waste incineration flue gas.

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On-line resonance-enhanced multiphoton ionization time-of-flight laser mass spectrometry for combined multi-component-pattern analysis and target-compound monitoring: non-chlorinated aromatics and chlorobenzene in flue gases of combustion processes

Cited by 17 publications

References 24 publications

On π-stacking, C-H/π, and halogen bonding interactions in halobenzene clusters: Resonant two-photon ionization studies of chlorobenzene

On π-stacking, C-H/π, and halogen bonding interactions in halobenzene clusters: Resonant two-photon ionization studies of chlorobenzene

π-Stacking, C–H/π, and Halogen Bonding Interactions in Bromobenzene and Mixed Bromobenzene–Benzene Clusters

A Mobile Mass Spectrometer for Comprehensive On-Line Analysis of Trace and Bulk Components of Complex Gas Mixtures: Parallel Application of the Laser-Based Ionization Methods VUV Single- Photon Ionization, Resonant Multiphoton Ioniza- tion, and Laser-Induced Electron Impact Ionization

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