Photodissociation of uracil.
We investigate the photochemistry and photodissociation dynamics of uracil by two-colour photofragment Doppler spectroscopy and by two-colour slice imaging at excitation wavelengths between 268 and 235 nm. We observe the loss of a hydrogen atom upon excitation into the pipi* state. The angular distribution indicates a statistical process, while the translational energy distribution agrees with a dissociation that takes place on the electronic ground state. The pipi* state most likely deactivates via the lower-lying npi* state. In addition there is evidence for a second pathway: direct decay of the pipi* state to the electronic ground state with subsequent dissociation. Experiments on uracil-1,3-D(2) show that there is no site selectivity in the dissociation process. No evidence was found for the direct dissociation via a pisigma* excited state that seems to be relevant in the photochemistry of adenine and many other heterocyclic molecules. Overall, the photochemistry of uracil is similar to that of thymine.
Schneider
Michael
M
University of Würzburg, Institute of Physical Chemistry, Am Hubland, D-97074, Würzburg, Germany.
Schon
Christof
C
Fischer
Ingo
I
Rubio-Lago
Luis
L
Kitsopoulos
Theofanis
T
D004735:Energy Transfer; D006571:Heterocyclic Compounds / Q000737:chemistry; D007700:Kinetics; D013058:Mass Spectrometry; D010777:Photochemistry; D010782:Photolysis; D013816:Thermodynamics; D013941:Thymine / Q000737:chemistry; D014498:Uracil / Q000737:chemistry*
D006571:Heterocyclic Compounds; D014498:Uracil; D013941:Thymine