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Atmospheric Pressure Laser Ionization Mass Spectrometry with Tunable UV Wavelength Utilizing an Optical Parametric Oscillator.
Anal Chem
January 2025
Joint Mass Spectrometry Centre/Chair of Analytical Chemistry, University of Rostock, 18059 Rostock, Germany.
To our knowledge, this study presents the first implementation of wavelength-resolved resonance-enhanced multiphoton ionization (REMPI) spectroscopy under atmospheric pressure ionization conditions using a high-resolution mass spectrometric system. Atmospheric pressure laser ionization MS spectroscopic measurements were conducted on over 70 different polycyclic aromatic hydrocarbons (PAHs) and hetero-PAHs (N, S, and O) in standard solutions, as well as three complex PAH-containing samples. The results demonstrate the successful transfer of REMPI spectroscopy from vacuum to atmospheric pressure conditions, maintaining spectral integrity without significant band broadening.
View Article and Find Full Text PDFUltraviolet Excitation of M-O (M = Phenalenone, Fluorenone, Pyridine, & Acridine) Complexes Resulting in O.
J Phys Chem A
April 2024
Department of Chemistry and Biochemistry 2500 California Plaza, Creighton University, Omaha, Nebraska 68178, United States.
In our experiment, a trace amount of an organic molecule (M = 1-phenalen-1-one, 9-fluorenone, pyridine, or acridine) was seeded into a gas mix consisting of 3% O with a rare gas buffer (He or Ar) and then supersonically expanded. We excited the resulting molecular beam with ultraviolet light at either 355 nm (1-phenalen-1-one, 9-fluorenone, or acridine) or 266 nm (pyridine) and used resonance enhanced multiphoton ionization (REMPI) spectroscopy to probe for the formation of O in the a-Δ state, O. For all systems, the REMPI spectra demonstrate that ultraviolet excitation results in the formation of O and the oxygen product is confirmed to be in the ground vibrational state and with an effective rotational temperature below 80 K.
View Article and Find Full Text PDFImpact of isoelectronic substitution on the excited state processes in polycyclic aromatic hydrocarbons: a joint experimental and theoretical study of 4,8-azaboranaphthalene.
Phys Chem Chem Phys
February 2024
Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
Substituting CC with the isoelectronic BN units is a promising approach to modify the optoelectronic properties of polycyclic aromatic hydrocarbons. While computational studies have already addressed trends in the electronic structure of the various isosteres, experimental data are still scarce. Here, the excited state spectroscopy and dynamics of 4,8-azaboranaphthalene were studied by picosecond time-resolved photoionization in a supersonic jet and analyzed with the aid of XMS-CASPT2 and time-dependent DFT calculations.
View Article and Find Full Text PDFThe Electronic Structures of Azaphenanthrenes and Their Dimers.
J Phys Chem A
February 2024
Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, Würzburg D-97074, Germany.
Insertion of a nitrogen atom modifies the electronic structures and photochemistry of polycyclic aromatic hydrocarbons by introducing nπ* states into the molecules. To better understand the electronic structures of isolated polycyclic aromatic nitrogen-containing hydrocarbons (PANHs) and their dimers as well as the influence of the position of the nitrogen atom in the molecule, we investigate three different azaphenanthrenes, benzo[]quinoline, benzo[]quinoline, and phenanthridine, in a joint experimental and computational study. Experimentally, resonance-enhanced multiphoton ionization (REMPI) spectroscopy is applied to characterize the excited electronic states.
View Article and Find Full Text PDFThe tautomer-specific excited state dynamics of 2,6-diaminopurine using resonance-enhanced multiphoton ionization and quantum chemical calculations.
Photochem Photobiol
December 2023
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA.
2,6-Diaminopurine (2,6-dAP) is an alternative nucleobase that potentially played a role in prebiotic chemistry. We studied its excited state dynamics in the gas phase by REMPI, IR-UV hole burning, and ps pump-probe spectroscopy and performed quantum chemical calculations at the SCS-ADC(2) level of theory to interpret the experimental results. We found the 9H tautomer to have a small barrier to ultrafast relaxation via puckering of its 6-membered ring.
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