Electronic structure of adenine and thymine base pairs studied by femtosecond electron-ion coincidence spectroscopy.
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The journal of physical chemistry. A, ISSN: 1089-5639, Vol: 111, Issue: 46, Page: 11743-9
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- Chemistry; RESOLVED PHOTOELECTRON-SPECTROSCOPY; NUCLEIC-ACID BASES; ULTRAFAST INTERNAL-CONVERSION; PROTON-TRANSFER PROCESSES; EXCITED-STATE DYNAMICS; ISOLATED DNA BASES; RNA BASES; MOLECULAR-DYNAMICS; LASER SPECTROSCOPY; AB-INITIO
Femtosecond pump-probe spectroscopy was combined with photoelectron-photoion coincidence detection to investigate the electronic structure and dynamics of isolated adenine (A) and thymine (T) dimers and the adenine-thymine (AT) base pair. The photoelectron spectra show that pipi* and npi* states are only weakly perturbed in the hydrogen-bound dimers as compared to the monomers. For cationic base pairs with internal energies greater than 1 eV, we observed considerable cluster fragmentation into protonated monomers. This process selectively removed signals from the npi* --> n-1 ionization channel in all dimers. The photoelectron spectra are compared to time-resolved mass spectra and confirm the assignment of short-lived pipi* and npi* populations in the adenine, thymine, and mixed AT dimers.