Photodissociation of pyrene dimer radical cation during the pulse radiolysis–laser flash photolysis combined method

Autor: Shingo Samori, Tetsuro Majima, Mamoru Fujitsuka
Rok vydání: 2012
Předmět:
Zdroj: Research on Chemical Intermediates. 39:449-461
ISSN: 1568-5675
0922-6168
DOI: 10.1007/s11164-012-0662-2
Popis: Photodissociation of pyrene (Py) dimer radical cation (Py 2 ∙+ ) giving pyrene radical cation (Py∙+) and Py and subsequent regeneration of Py 2 ∙+ by association of Py∙+ and Py were directly observed during the pulse radiolysis–laser flash photolysis combined method at room temperature. When Py 2 ∙+ was excited at the local excitation band with the 532-nm laser flash, the rapid growth and decay of monomeric Py∙+ were observed at 460 nm. The dissociation of Py 2 ∙+ proceeded via a one-photon process to give the ground-state Py∙+(D0) and Py in the quantum yield (Φdiss) of (2.9 ± 0.9) × 10−3. It was shown that Py∙+ decayed with a time constant of several tens of nanoseconds, indicating that the association of Py∙+ with Py regenerating Py 2 ∙+ proceeds at a diffusion-controlled rate. The photodissociation proceeded from the lowest excited state of Py 2 ∙+ , even when Py 2 ∙+ was excited to the higher excited state. The difference between the Φdiss value of Py 2 ∙+ and that previously reported for naphthalene dimer radical cation (Np 2 ∙+ ) is discussed.
Databáze: OpenAIRE
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