Resonant two-photon ionization spectroscopy in supersonic beams for discrimination of disubstituted benzenes in mass spectrometry

Sin, Chung Hang; Tembreull, Roger.; Lubman, David M.

doi:10.1021/ac00278a033

Cited by 58 publications

(29 citation statements)

References 32 publications

(37 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To verify the mobile unit with a first series of test substances, we used benzene, toluene, and the mono-and dichlorinated derivates for which the REMPI spectra are well defined [11,13,14].…”

Section: Some Laboratory Results Indicating Selectivity On-line Capamentioning

confidence: 99%

DLR-Jet REMPI - Ultrasensitive Monitor for Process Control in Thermal Processes

Oser¹,

Thanner²,

Grotheer³

1998

Chem. Eng. Technol.

View full text Add to dashboard Cite

Process control requires sensitive and selective on-line monitors for species concentrations. This applies in particular if feeds of varying compositions are involved. Current REMPI (= Resonance Enhanced Multiphoton Ionization) mass spectrometers would be suitable instruments in terms of selectivity and on-line capability, their sensitivities, however, are generally too low. By contrast, the DLR-Jet REMPI geometry provides a major sensitivity improvement. An extended test series shows that this is achieved without paying a price in terms of selevtivity. The paper provides some of these results and lists up the development steps needed to make Jet REMPI an instrument suitable for industrial use. Process Optimization and Control for Emission AbatementCurrent pollutant abatement technologies for thermal plants have mostly been developed in the context of incineration. Air pollutant cleaning devices (APCs) consist of wet or dry scrubbers, beds of activated carbon or catalytic converters. They are generally simply added to the primary process in order to trap or destroy pollutants formed there. Hence, they are called end-of-the-pipe techniques. The complementary approach is given by head-end techniques aiming at the reduction of pollutant formation. This can be accomplished by optimizing the process through carefully tailoring its design and operation parameters. With hydrocarbon flames, chemical kinetic models and models dealing with transport of heat and matter are now sufficiently accurate to enable such tailoring. In incineration, however, kinetic mechanisms are still poorly understood so that modeling is widely replaced by empirism.The other problem quite often involved in incineration is that the composition of the feed is subject to rapid changes. This requires that such an optimization has to be based on time-resolved concentration measurements of relevant species in the process gas. With a suitable computer program, these signals can be used to drive control means (e.g., air distribution flaps) so as to continuously optimize the process. This type of process control could not be carried out in the past for lack of sufficiently sensitive monitors.Some examples are given to illustrate the present situation. One of the very rare exceptions from the more current end-of-the-pipe technologies in incineration has been presented recently in Japan [1]. In an attempt to reduce NO emissions the re-burn technology, which has been developed for hydrocarbon combustors, was adopted to an incinerator. To this end, a re-burn zone was established above the grate using an additional natural gas burner. It was found that this technique not only diminished the NO release but also led to a significant reduction of dioxins as measured further downstream. Obviously, fuel-staging had an advantageous effect on precursors to dioxin formation, such as chlorophenols. Consequently, by continuously monitoring these species it should be possible to control the process in a way as to minimize precursor concentrations and hence dioxin release...

show abstract

Section: Some Laboratory Results Indicating Selectivity On-line Capamentioning

confidence: 99%

DLR-Jet REMPI - Ultrasensitive Monitor for Process Control in Thermal Processes

Oser¹,

Thanner²,

Grotheer³

1998

Chem. Eng. Technol.

View full text Add to dashboard Cite

show abstract

“…These ratios are much higher than that of~3 for the one-photon absorption coefficients at 193 om [34); however, the much higher density of states in So of toluene should lead to more rapid excited state relaxation after absorption of a single photon [35]. Aromatic molecules with substituents such as CH 3 or NH 2 have low quantum yields indicative of short-lived excited states that undergo rapid radiationless rela xation [11,22]. Increasing the power enhances the probability of absorption of a second photon before relaxation, thereby greatly enhancing the ion yield for toluene.…”

Section: Hs Isomers Cycloheptatriene and Toluene Have Sim-mentioning

confidence: 99%

“…Multiphoton ionization has be en used extensively for pr obing the str ucture of gas phase molecules [1][2][3][4][5]. Using a wavelength in resonance with an accessible electronic state of the mol ecule can give high isomeri c or even isotopic selectivity [1][2][3][4][5][6][7][8][9][10][11][12]. Such ionization efficiencies can approach 100% [4] as absorption of the second photon causes excitation to the continuum of preionization states.…”

mentioning

confidence: 99%

193 nm Laser photoionization and photodissociation for isomer differentiation in Fourier-transform mass spectrometry

Williams

McLafferty

1990

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

Energetic (6.4 eV) multiphoton ionization (MPI) or photodissociation, effected interchangeably in a Fourier-transform mass spectrometer, can differentiate isomers that yield similar electron ionization spectra. Selectivity is shown for isomers of C7H8, C7H9N, C7H7F, C8H10, but not of C6H3Cl{3} and C14H10. The contrasting MPI fragmentations and ionization efficiencies, as well as high sensitivities, are of substantial analytical utility. The high ionization efficiency makes possible high resolution MPI spectra, such as 470,000 (FWHH) for the molecular ion of anthracene, from a single laser pulse.

show abstract

“…[1][2][3][4] However, one can also use it directly as an analytical technique by measuring the ionization current with an electrode. In the REMPI process, a molecule is excited by a photon, or photons, whose energy is in resonance with an electronic state of the molecule.…”

Section: Introductionmentioning

confidence: 99%

Resonance-enhanced multiphoton ionization for real-time monitoring of trichloroethylene formed by degradation of tetrachloroethylene using zero-valent zinc

et al. 2004

View full text Add to dashboard Cite

Resonance-enhanced multiphoton ionization ͑REMPI͒ is investigated as a potential technique for realtime monitoring of selected volatile organochloride compounds ͑VOCs͒. In a proof-of-concept experiment, the progress of the reductive-degradation of tetrachloroethylene ͑PCE͒ to trichloroethylene ͑TCE͒ by zero-valent zinc was monitored by REMPI measurements performed in the headspace above the PCE solution. Two-photon resonant REMPI spectra of TCE and PCE were recorded over the wavelength range 305-320 nm. The concentrations of PCE and TCE in the headspace were monitored by measurement of the ionization signal with 315.64-and 310.48-nm excitation for PCE and TCE, respectively. Calibration curves yielded a linear range of more than 2 orders of magnitude for both compounds. The REMPI headspace results agreed well with the solution-phase results from gas chromatography analysis, which was used for independent verification of the progress of the reaction.

show abstract

Resonant two-photon ionization spectroscopy in supersonic beams for discrimination of disubstituted benzenes in mass spectrometry

Cited by 58 publications

References 32 publications

DLR-Jet REMPI - Ultrasensitive Monitor for Process Control in Thermal Processes

DLR-Jet REMPI - Ultrasensitive Monitor for Process Control in Thermal Processes

193 nm Laser photoionization and photodissociation for isomer differentiation in Fourier-transform mass spectrometry

Resonance-enhanced multiphoton ionization for real-time monitoring of trichloroethylene formed by degradation of tetrachloroethylene using zero-valent zinc

Contact Info

Product

Resources

About