Excimer Luminescence From Nonresonantly Excited Pyrene and Perylene Molecules in Solution

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• 作者：Kazuya Nakagawa ; Yudai Numata ; Heisuke Ishino ; Daichi Tanaka ; Takayoshi Kobayashi ; Eiji Tokunaga
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：November 14, 2013
• 年：2013
• 卷：117
• 期：45
• 页码：11449-11455
• 全文大小：474K
• 年卷期：v.117,no.45(November 14, 2013)
• ISSN：1520-5215

文摘

By nonresonant excitation below the absorption edge of pyrene and perylene molecules in solution, efficient excimer luminescence is observed. For perylene in solution, there are two kinds of nonresonant excimer emission that closely resemble Y- and E-emissions in perylene crystal and perylene in polymer. The concentration dependence of the photon flux density of monomer and excimer emission is reasonably explained by a simple model with a few fitting parameters based on the ordinary excimer formation process, in which the excited-state monomer interacts with a ground-state monomer. Observed quantum efficiency of excimer formation is by orders of magnitude higher than that expected if a monomer is excited from thermally populated vibrational levels. The experimental evidence for direct resonant excitation of excimers in perylene nanocrystals is obtained from the absence of anti-Stokes emission. This is due to a symmetry-breaking effect close to crystal surface, suggesting that excimers are formed through a more efficient process in solution, such as resonant excitation of weakly interacting molecules with a symmetry-broken intermolecular configuration.