Femtosecond Pump-Probe Spectroscopy

Femtosecond Pump-Probe Spectroscopy

Femtosecond Pump-Probe Spectroscopy

Biological life is based on a specific type of “left-handed” amino acids, and no one knows why these amino acids – and not the “right-handed” – are found to be the basis of biology. A hypothesis is, that circular polarized ultra-violet light could have participated in the selective photolysis of the amino acids, whereby excess of left-handed amino acids were created.

Another experiment investigates the release of large amounts of energy after a chemical reaction. In water, this energy is dissipated to the surrounding molecules very quickly (on fs or ps scale). The exact mechanisms behind the crucial relaxation process, that happen through hydrogen-bonds, are unknown. By starting a chemical event using a UV pulse, the dynamics can be probed on a molecular timescale with an infrared femtosecond pulse, probing the development in the solvent shortly after the event.

Thermoelectric materials exhibit a special and weak interaction between the movement of the electrons (electrical conduction) and the crystal lattice vibrations (thermal conduction). We believe that this interaction can be probed by using femtosecond lasers. With a UV pulse, we excite the electrons, and by measuring the subsequent reflection coefficient of the material, we can determine the coupling between the electrons and the lattice.

Relevant publications:

A. Gadegaard et al. Spectroscopy and dynamics of aqueous nitrogen dioxide. J. Chem. Phys. 141, 064310 (2014)

J. B. Nielsen et al. Vibrational Dynamics of Deoxyguanosine 5’-Monophosphate following UV Excitation, Chemistry Chemical Physics, 13, 13821-13826 (2011)

S.R. Keiding et. al. When molecules meet: A femtosecond study of the protonation of a base, Chemical Physics Letters, 390, 94-97 (2004)