کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
29090 44118 2008 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Excited state processes of nitrobenzaldehydes probed by ultrafast fluorescence and absorption spectroscopy
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی بیو مهندسی (مهندسی زیستی)
پیش نمایش صفحه اول مقاله
Excited state processes of nitrobenzaldehydes probed by ultrafast fluorescence and absorption spectroscopy
چکیده انگلیسی

We have investigated the isomers ortho-, meta-, and para-nitro-benzaldehyde (NBA) by means of ultrafast emission and absorption spectroscopy. The fluorescence dynamics of all three molecules are very similar and feature bi-phasic emission decays with time constants of <100 fs and ∼1∼1 ps. The first process goes along with a strong loss of oscillator strength, which we assume is the result of a non-radiative π1π∗→n1π∗ transition. These commonalities are contrasted by qualitatively different transient absorption signatures: For the photo-reactive isomer o-NBA, signatures of a ketene intermediate in the electronic ground state are observed. Its formation time matches the slower component of the emission decay. The ketene afterwards experiences pronounced cooling dynamics on the picosecond timescale followed by its decay in the nanosecond regime. For the non-reactive isomers m- and p  -NBA, time constants with values similar to the ones derived from the emission experiment are found in the absorption experiment. In addition, at later delay times, a distinct spectral signature is observed for both isomers which decays within ∼1∼1 ns and is assigned to a triplet state. This triplet decay is preceded by a process on the 10 ps timescale which we tentatively assign to a transition within the triplet manifold.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 199, Issues 2–3, 25 September 2008, Pages 274–281
نویسندگان
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