2004 Fiscal Year Final Research Report Summary
Elucidation of Reaction Mechanism of Photochemistry in Solution Phase Studied with Quantitative Measurements of Excess Energy
| Project/Area Number |
15350013
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Kobe University |
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Principal Investigator |
MIZUTANI Yasuhisa Kobe University, Molecular Photoscience Research center, Associate Professor, 分子フォトサイエンス研究センター, 助教授 (60270469)
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| Project Period (FY) |
2003 – 2004
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| Keywords | vibrational relaxation / resonance Raman spectroscopy / time-resolved spectroscopy |
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| Research Abstract |
Time-resolved resonance Raman (TR^3) spectroscopy is particularly suited for probing the vibrational state dynamics of colored molecules in solution phase. The intensity ratio of anti-Stokes and Stokes scattering is expected to provide the most direct information about relative vibrational populations. Here, we applied this technique to explore the vibrational energy redistribution of heme in the globin matrix upon photolysis of carbonmonoxy myoglobin (MbCO). An analysis of the temporal changes of anti-Stokes band intensities showed that the anti-Stokes intensity develops within the instrument response time. The instrument response was deconvoluted from the decay of the anti-Stokes intensity using a Gaussian fit to the cross correlation signal. This analysis obtained the decay constants of 1.1±0.6 ps for the v_4 band and 1.9±0.6 ps for the v_7 band. Because there is no intensity change in the Stokes v_4 and v_7 bands in the 3 to 50-ps time range, the observed intensity decay in the anti-Stokes v_4 and v_7 bands can be ascribed to vibrational energy relaxation. The decay rates of in-plane modes including v_3, v_4, v_6, and v_7 agree well with the rates calculated under the assumption of the statistical distribution. This suggests exchanges of vibrational energy among these modes are very fast. In contrast, two out-of-plane vibrational modes exhibited deviations from the line. Moreover, among the in-plane vibrations, v_5 mode showed very slow decay of the anti-Stokes intensity. Slow intensity decay of the anti-Stokes v_5 mode was also observed for ferric cytochrome c. We ascribed these deviations to weak anharmonic coupling among the vibrational modes. The present results cannot be explained with a single vibrational temperature. In other words, the results show that intramolecular and intermolecular processes are not temporally separated for the heme.
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Research Products
(3 results)
