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Title: Ultraviolet Excitation of M-O 2 (M = Phenalenone, Fluorenone, Pyridine, & Acridine) Complexes Resulting in 1 O 2
In our experiment, a trace amount of an organic molecule (M = 1H-phenalen-1-one, 9-fluorenone, pyridine, or acridine) was seeded into a gas mix consisting of 3% O2 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 (1H-phenalen-1-one, 9-fluorenone, or acridine) or 266 nm (pyridine) and used resonance enhanced multiphoton ionization (REMPI) spectroscopy to probe for formation of O2 in the a 1Δg state, 1O2. For all systems, the REMPI spectra demonstrates that ultraviolet excitation results in formation of 1O2 and the oxygen product is confirmed to be in the ground vibrational state and with an effective rotational temperature below 80 K. We then recorded the velocity map ion image of the 1O2 product. From the ion images we determined the center-of-mass translational energy distribution, P(ET), assuming photodissociation of a bimolecular M-O2 complex. We also report results from electronic structure calculations that allow for a determination of the M-O2 ground state binding energy. We use the complex binding energy, the energy to form 1O2, and the adiabatic triplet energy for each organic molecule to determine the available energy following photodissociation. For dissociation of a bimolecular complex, this available energy may be partitioned into either center-of-mass recoil or internal degrees of freedom of the organic moiety. We use the available energy to generate a Prior distribution, which predicts statistical energy partitioning during dissociation. For low available energies, less than 0.2 eV, we find the statistical prediction is in reasonable agreement with the experimental observations. However, at higher available energies the experimental distribution is biased to lower center-of-mass kinetic energies compared with the statistical prediction, which suggests the complex undergoes vibrational predissociation.  more » « less
Award ID(s):
2150871
PAR ID:
10503677
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Journal of Physical Chemistry A
Date Published:
Journal Name:
The Journal of Physical Chemistry A
Volume:
128
Issue:
15
ISSN:
1089-5639
Page Range / eLocation ID:
2971 to 2981
Subject(s) / Keyword(s):
singlet oxygen UV-A UV-B resonance enhanced multiphoton ionization REMPI velocity map ion imaging VMI
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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