Publications by authors named "Mathias Steglich"

Article Synopsis
  • An innovative high vacuum interface called liq-PEPICO is introduced for studying the liquid phase through photoelectron photoion coincidence spectroscopy at the Swiss Light Source.
  • The setup includes a vaporizer that creates aerosols, forming a molecular beam that is then analyzed using ion velocity map imaging and various vaporization parameters to enhance sensitivity.
  • The study successfully records mass spectra and threshold photoelectron spectra for specific compounds, showing accurate reproductions and allowing for the investigation of reactions like aldol condensation in real-time.
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We studied the thermal decomposition of dimethyl carbonate (DMC, CHO) in a flash vacuum pyrolysis reactor in the 1100-1700 K range. The reaction products and intermediates were probed by vacuum ultraviolet synchrotron radiation in a photoelectron photoion coincidence (PEPICO) spectrometer to record isomer-specific photoion mass-selected threshold photoelectron (ms-TPE) spectra. Reaction pathways were explored using quantum chemical calculations, which confirmed the experimental observation that the intramolecular migration of a methyl group, yielding dimethyl ether (DME, CHO) and carbon dioxide, dominates the initial unimolecular decomposition chemistry.

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Reactive species, such as PO and HOPO, are considered of upmost importance in flame inhibition and catalytic combustion processes of fuels. However, the underlying chemistry of their formation remains speculative due to the unavailability of suitable analytical techniques that can be used to identify the transient species which lead to their formation. This study elucidates the reaction mechanisms of the formation of phosphoryl species from dimethyl methyl phosphonate (DMMP) and dimethyl methyl phosphoramidate (DMPR) under well-defined oxidative conditions.

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Excited xylyl (methyl-benzyl) radical isomers have been studied by femtosecond time-resolved photoelectron spectroscopy and mass spectrometry. Depending on the substitution we find different deactivation channels after excitation into the D3(2A'') state (310 nm, 4 eV). While the ortho and para isomer exhibit deactivation rates similar to the benzyl radical, meta-xylyl sticks out and depletes twice as fast into the vibrationally hot ground state.

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Resonant one-color two-photon ionization spectroscopy and mass-selected threshold photoelectron spectroscopy were applied to study the electronic doublet states of the three xylyl (methyl-benzyl) radicals above 3.9 eV as well as the singlet and triplet states of the cations up to 10.5 eV.

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The meta-xylylene diradical m-CH is a prototypical organic triplet that represents a building block for organic molecule-based magnets and also serves as a model compound for test and refinement of quantum chemical calculations. Flash vacuum pyrolysis of 1,3-bis-iodomethyl-benzene (m-CHI) produces m-CH in gas phase; we used photoelectron spectroscopy to probe the first two electronic states of the radical cation, and resolve the vibrational fine structure of the ground state band. The determined adiabatic ionization energy of m-CH is (7.

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The photodissociation dynamics of the CH isomers ortho- and para-xylyl are investigated in a free jet. The xylyl radicals are generated by flash pyrolysis from 2-(2-methylphenyl)- and 2-(4-methylphenyl) ethyl nitrite and are excited into the D state. REMPI- spectra show vibronic structure and the origin of the transition is identified at 32 291 cm for the para- and at 32 132 cm for the ortho-isomer.

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The gas phase detection of benzocyclopropenyl is reported. In this aromatic resonance stabilized radical, a large angular strain is present due to a three-membered ring annelated to a benzene. The resonant two-color two-photon ionization technique is used to record the D1((2)A2) ← D0((2)B1) electronic transition of this radical after the in situ synthesis in a discharge source.

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The gas-phase electronic spectra of two resonantly stabilized radicals, 1-indanyl (C9H9) and 1-methyl-1-indanyl (C10H11), have been recorded in the visible region using a resonant two-color two-photon ionization (R2C2PI) scheme. The D1(A″) ← D0(A″) origin bands of 1-indanyl and 1-methyl-1-indanyl radicals are observed at 21157 and 20565 cm(–1), respectively. The excitation of a′ vibrations in the D1 state is observed up to ∼1500 cm(–1) above the origin band in both cases.

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The 1(3)Σu (-)←X(3)Σg (-) transition of linear HC5H (A) has been observed in a neon matrix and gas phase. The assignment is based on mass-selective experiments, extrapolation of previous results of the longer HC2n+1H homologues, and density functional and multi-state CASPT2 theoretical methods. Another band system starting at 303 nm in neon is assigned as the 1(1)A1←X˜(1)A1 transition of the cumulene carbene pentatetraenylidene H2C5 (B).

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Ultraviolet electronic transitions of the linear carbon chains C6, C7, C8, and C9 were measured in the gas phase by a mass-resolved 1 + 1 resonant two-photon ionization technique using a picosecond laser. Broad absorptions with band maxima at 230.2 and 259.

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We report on the characterization of dibenzo[cde,opq]rubicene (C(30)H(14)). The molecule was studied in solution at room temperature with absorption spectroscopy in the visible (vis) and ultraviolet (UV) wavelength ranges, and with emission spectroscopy. The infrared (IR), visible, ultraviolet, and vacuum ultraviolet (VUV) absorption spectra of a thin film were measured also at room temperature.

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Absorption spectra of hexa-peri-hexabenzocoronene isolated in rare-gas matrices are reported for the wavelength range between 200 and 500 nm. Measurements were carried out in neon and in argon at 5.8 and 12.

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The spectroscopic characterization of corannulene (C(20)H(10)) is carried out by several techniques. The high purity of the material synthesized for this study was confirmed by gas chromatography-mass spectrometry (GC-MS). During a high-performance liquid chromatography (HPLC) process, the absorption spectrum of corannulene in the ultraviolet (UV) and visible (vis) ranges is obtained.

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