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Code:
MP09
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Time Slot/Poster Number:
153
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Session:
Time Resolved Raman
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Local Structure and Microscopic Thermal Diffusion in Ionic Liquids Studied with Picosecond Time-resolved Raman Spectroscopy
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| Kyousuke Yoshida1; Koichi Iwata2; Hiro-o Hamaguchi1, 3
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1The University of Tokyo, Tokyo, Japan; 2Gakushuin University, Tokyo, Japan; 3National Chio Tung University, Hsinchu, Taiwan
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| View Abstract PDF |
| Summary |
Microscopic thermal diffusion in ionic liquids is measured with picosecond time-resolved Raman spectroscopy; the 1570-cm-1 Raman band of S1 trans-stilbene can be used as a “picosecond Raman thermometer” because the peak position of this band changes linearly with temperature. In this study, the lack of correlation between the macroscopic and microscopic thermal properties in ionic liquids is explained in terms of the presence of the local structure. The volume of the local structure formed in ionic liquids is estimated from the analysis based on the diffusion equation of heat.
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Code:
MP09
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Time Slot/Poster Number:
154
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Session:
Time Resolved Raman
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Unravelling the Fast Photocyclisation Reaction Mechanism(s) of 2-Benzoylpyridine in Aqueous Solvent by Time-resolved Spectroscopy
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| Yong DU1, 2; Jiadan XUE1, 3; Mingde LI1; Xiangguo GUAN1; David W. McCamant2; David Lee Phillips1
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1Dept. of Chemistry, The University of Hong Kong, Hong Kong, P. R. China; 2Dept. of Chemistry, The University of Rochester, Rochester, NY; 3Dept. of Chemistry, The Ohio State University, Columbus, OH
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| View Abstract PDF |
| Summary |
A combined femtosecond transient absorption (fs-TA) and nanosecond time-resolved Resonance Raman (ns-TR3) spectroscopic investigation of the photoreaction of 2-benzoylpyridine in acetonitrile, neutral, basic and acidic aqueous solvents is reported. Some new species generated in the aqueous solvents observed for the first time and characterised by time-resolved vibrational spectroscopy in conjunction with results from DFT calculations. The detailed fast photocyclisation mechanism(s) of 2-benzoylpyridine in aqueous solvents after UV laser photolysis is obtained.
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Code:
MP09
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Time Slot/Poster Number:
155
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Session:
Time Resolved Raman
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Ultrafast Vibrational Spectroscopy Study of the Photochemistry of 2-Methoxy-6-Methoxycarbonylphenyl Azide
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| Jiadan Xue; Hoi Ling Luk; Matthew S. Platz
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Department of Chemistry, The Ohio State University, Columbus, Ohio
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| View Abstract PDF |
| Summary |
An ultrafast time resolved infrared spectroscopic study of the photochemistry of 2-methoxy-6-methoxycarbonylphenyl azide in organic solvent, following 270 nm excitation at room temperature is reported. The singlet and triplet nitrenes and the ketenimine were observed in the ultrafast infrared spectra. The kinetic data showed that the ketenimine is generated with time constants of ~700 ps from cold singlet nitrene, and ~16 ps from hot singlet nitrene. The fast formation rate of ketenimine from cold singlet nitrene suggests that the electron-donating group decreases the ring expansion activation barrier, and balances the steric effect.
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Code:
MP09
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Time Slot/Poster Number:
156
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Session:
Time Resolved Raman
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Water Concentration Dependent Photochemistry of Ketoprofen in Neutral Aqueous Solutions
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| Ming-De Li1; Yong Du2; Jiadan Xue3; David Lee Phillips1
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1University of Hong Kong, Hong Kong, China; 2University of Rochester, Rochester, New York; 3Ohio State University, Columbus, Ohio
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| View Abstract PDF |
| Summary |
The rate constants and reaction mechanism of ketoprofen were observed to be greatly dependent on the concentration of the solvent in neutral aqueous solutions with varying water concentrations. In neat acetonitrile and solvents with low concentrations of water, ketoprofen displays benzophenone-like photochemistry. However, in solvents with very high concentrations of water, the triplet state ketoprofen is first seen and then experiences a very fast decarboxylation process to produce a triplet protonated biradical carbanion species. For solvents with moderate higher water concentrations, the hydrogen abstraction and decarboxylation processes are two competitive pathways with different rate constants.
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Code:
MP09
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Time Slot/Poster Number:
157
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Session:
Time Resolved Raman
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Time-Resolved Raman Spectroscopy Through ICCD Detection: Examples On Al2O3 : Cr3+
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| Yeny Alexandra Tobon-Correa; Denis Bormann; Aurelien Canizares; Nicole Raimboux; Patrick Simon
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CNRS UPR 3079, CEMHTI, Orleans, France
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| View Abstract PDF |
| Summary |
Time-resolved Raman Spectroscopy has been extensively used to probe photophysical and photochemical properties of excited states in solution phase, but it has rarely been applied to solids due to photo-degradation and relatively low sensitivity of the instruments employed.
Here, we demonstrate a time-resolved Raman technique that combines the two-color system, the detection by an ICCD camera, and the Raman microscopy, giving good optic and temporal resolution, with recovery times in the nanosecond range. The advantages of this approach are demonstrated on Al2O3:Cr3+, obtaining the temporal evolution of the excited state transition Ē→2Ā and the time-dependence of the luminescence.
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Code:
MP09
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Time Slot/Poster Number:
158
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Session:
Time Resolved Raman
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Energy Transfer Characteristics of Lipid Bilayer Membrane in Liposome Studied with Picosecond Time-Resolved Raman Spectroscopy
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| Yuki Nojima1; Kyousuke Yoshida2; Hiro-o Hamaguchi2, 3; Koichi Iwata1
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1Gakushuin University, Tokyo, Japan; 2The University of Tokyo, Tokyo, Japan; 3National Chio Tung University, Hsinchu, Taiwan
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| View Abstract PDF |
| Summary |
The cooling kinetics of S1 trans-stilbene solubilized in liposome lipid bilayer was measured with picosecond time-resolved Raman spectroscopy. We estimated the thermal diffusivity inside the liposome lipid bilayer from the correlation between the cooling rate of S1 trans-stilbene and thermal diffusivity of the solvent. The estimated thermal diffusivity was around 9.5 x 10-8 m2 s-1, which is considerably larger than that of alkanes. It is possible that the thermal diffusivity inside the liposome lipid bilayer is influenced by the surrounding water.
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Code:
MP09
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Time Slot/Poster Number:
159
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Session:
Time Resolved Raman
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Early Steps in Cytochrome C Unfolding Probed by Nanosecond Laser Induced T-jump/UV Resonance Raman Spectroscopy
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| Gurusamy Balakrishnan; Ying Hu; Thomas G. Spiro
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Department of Chemistry, Seattle, WA
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| View Abstract PDF |
| Summary |
Cytochrome c (cyt c), the electron-transferring heme protein of mitochondria, has played a large role in studies of the earliest events in protein folding. T-jump/UVRR spectroscopy on unfolding of cyt c at pH 3 reveal time constants of 2.2 and 3.2 microseconds for beta-sheet formation and intensity decrease of phenylalanine band respectively. Phenylalanine also show a nanosecond phase at 110 ns similar to apomyoglobin, which has been attributed to solvent penetration. The formation of beta-sheet possibly from the 40’s omega-loop in microsecond time scale is analogous to intrachain diffusion phase observed from folding studies.
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