Chemistry Department Seminar

This work investigates the femtosecond laser induced associative photodesorption of hydrogen, and deuterium from a Ruthenium metal surface. Many interesting features of this reaction were explored by experimentalists: (i) a huge isotope effect in the desorption probability of H2 and D2, (ii) the desorption yield increases non¬linearly with the applied visible laser fluence, and
(iii) unequal energy partitioning to different degrees of freedom. These peculiarities are due to the fact that an ultrashort vis pulse creates hot electrons in the metal. These hot electrons then transfer energy to adsorbate vibrations which leads to desorption. This means that, surfaces introduce additional channels for energy exchange which makes the control of surface reactions more difficult than the control of reactions in the gas phase. One of the goals of the present work is to suggest, on the basis of theoretical simulations, strategies to control/enhance the photodesorption yield. For this purpose, we suggest a hybrid scheme to control the reaction, where the adsorbate vibrations are initially excited by an infrared (IR) pulse, prior to the vis pulse. Both adiabatic and non¬adiabatic representations for photoinduced desorption problems are employed here.
1 T. Vazhappilly, T. Klamroth, P. Saalfrank, R. Hernandez, J. Phys. Chem. C 113, 7790(2009).
2 T. Vazhappilly, S. Beyvers, T. Klamroth, M. Luppi, P. Saalfrank, Chem. Phys. 338, 299(2007).