title: Disentangling intrinsic ultrafast excited-state dynamics of cytosine tautomers.
abstract: Gas-phase ultrafast excited-state dynamics of cytosine, 1-methylcytosine, and 5-fluorocytosine were investigated in molecular beams using femtosecond pump-probe photoionization spectroscopy to identify the intrinsic dynamics of the major cytosine tautomers. The results indicate that, upon photoexcitation in the first absorption band, the cytosine enol tautomer exhibits a significantly longer excited-state lifetime than its keto and imino counterparts. The initially excited states of the cytosine keto and imino tautomers decay with sub-picosecond dynamics for excitation wavelengths shorter than 300 nm, whereas that of the cytosine enol tautomer decays with time constants ranging from 3 to 45 ps for excitation between 260 and 285 nm.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, ROC.
authors.forename: Jr-Wei
authors.initials: JW
authors.lastname: Ho
authors.forename: Hung-Chien
authors.initials: HC
authors.lastname: Yen
authors.forename: Wei-Kuang
authors.initials: WK
authors.lastname: Chou
authors.forename: Chih-Nan
authors.initials: CN
authors.lastname: Weng
authors.forename: Li-Hao
authors.initials: LH
authors.lastname: Cheng
authors.forename: Hui-Qi
authors.initials: HQ
authors.lastname: Shi
authors.forename: Szu-Hsueh
authors.initials: SH
authors.lastname: Lai
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Cheng
mesh_terms: D003596:Cytosine / Q000031:analogs & derivatives / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D011789:Quantum Theory; D013057:Spectrum Analysis; D013237:Stereoisomerism
chemical_list: D003596:Cytosine