Ab Initio Molecular Dynamics and Time-Resolved Photoelectron Spectroscopy of Electronically Excited Uracil and Thymine

详细信息    查看全文

• 作者：Hanneli R. Hudock ; Benjamin G. Levine ; Alexis L. Thompson ; Helmut Satzger ; D. Townsend ; N. Gador ; S. Ullrich ; Albert Stolow ; Todd J. Mart&iacute ; nez
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：August 30, 2007
• 年：2007
• 卷：111
• 期：34
• 页码：8500 - 8508
• 全文大小：520K
• 年卷期：v.111,no.34(August 30, 2007)
• ISSN：1520-5215

文摘

The reaction dynamics of excited electronic states in nucleic acid bases is a key process in DNA photodamage.Recent ultrafast spectroscopy experiments have shown multicomponent decays of excited uracil and thymine,tentatively assigned to nonadiabatic transitions involving multiple electronic states. Using both quantumchemistry and first principles quantum molecular dynamics methods we show that a true minimum on thebright S₂ electronic state is responsible for the first step that occurs on a femtosecond time scale. Thus theobserved femtosecond decay does not correspond to surface crossing as previously thought. We suggest thatsubsequent barrier crossing to the minimal energy S₂/S₁ conical intersection is responsible for the picoseconddecay.