Work Group Prof. Dr. F. Temps

Femtosecond Photophysical and Photochemical Dynamics

Femtosecond Photophysical and Photochemical Dynamics of DNA Building Blocks

DNA helix

The DNA bases adenine (A), cytosine (C), guanine (G), and thymine (T) stand out for their extraordinary photochemical stabilities which arise owing to ultrafast electronic deactivation processes. After absorption of a UV photon, the molecules are thereby returned to their ground electronic states before chemical reactions in the excited states can cause profound damage. We are studying the underlying ultrafast dynamics of the different building blocks of DNA by femtosecond fluorescence and absorption spectroscopies.





Ultrafast Reaction Dynamics of Photochromic Molecular Switches


Photochromic molecules can be reversibly interconverted, i.e., switched, between two or more isomeric forms with distinctive physical and chemical properties by absorption of light at different wavelengths. The light-driven transformations are of great interest for the development of optimal memory and information storage devices, for applications as molecular switches, or for designing molecular machines. Towards these ends, however, one needs detailed information on the underlying ultrafast photochemical reaction dynamics. In this project within the new Collaborative Research Centre SFB 667 "Function by Switching", we use femtosecond spectroscopy as the method of choice to directly monitor the absorption and emission changes of the molecules during their light-induced transformations with time resolutions of 50 fs (5x10-14 s) or even better.




Femtosecond Time-Resolved Mass Spectrometry and Photoelectron Imaging


Femtosecond time-resolved mass spectrometry and photoelectron imaging of electronically excited polyatomic molecules allow us to monitor the excited state populations of the molecules as function of time and obtain very detailed pictures of their electronic dynamics. Of special interest are halogenated aromatics and N-containing heteroaromatic molecules which are important building blocks of many biological molecules.