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Jen, Myungsam,Lee, Sebok,Jeon, Kooknam,Hussain, Shafqat,Pang, Yoonsoo American Chemical Society 2017 The Journal of physical chemistry B Vol.121 No.16
<P>We report time-resolved stimulated Raman spectra of alizarin in DMSO solution with, 403 nm excitation. Upon photo excitation, the intramolecular proton transfer reaction of alizarin occurs in 70-80 fs, which is, confirmed by both the population growth and the frequency and bandwidth changes of skeletal vibrational modes of alizarin. Interestingly, the vibrational frequencies of v(C= C) and v(C=O) show opposite shifts during the reaction, which may implicate changes, in the resonance structure, of anthraquinone and the attached-carbonyl group. Vibrational relaxation in the potential surface of the proton transferred tautomer of alizarin and the population decay occurring-with two distinct time scales were also observed in addition to the solvation dynamics of DMSO solvent molecules.</P>
Myungsam Jen,이세복,방윤수 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.3
Time-resolved electronic and vibrational spectroscopy has been applied to understand ultrafast excited state dynamics of all-trans-retinal. Femtosecond transient absorption spectroscopy provides an overview of the excited-state dynamics of all-trans-retinal, and femtosecond-stimulated Raman and infrared absorption measurements, which have not been reported previously, provide further details of the structural changes in the excited states. Three singlet excited states and one triplet excited state have been identified from these experimental results, which are in good agreement with many previous reports. A change in the energy order of the singlet excited state of all-trans-retinal between in polar and nonpolar solvents abruptly modifies the excited state dynamics. The intersystem crossing to the T1 state from the S1 state (nπ*) almost disappears in polar solvents, whereas the fluorescence from S3 and S2 states (ππ*) is almost absent in nonpolar solvents.