Femtochem

FEMTOCHEMISTRY LECTURE REVIEW

Femtochemistry is about doing chemistry with femtosecond lasers that typically allow the observation of very short processes in real time to the order of femtoseconds which are equal to a 10-15 part of a second. It is a way of understanding the underlying, basic chemical processes like making and breaking bonds and using this knowledge to control and design their effects towards a prospective target. One practical key target in surface science could be for example cleaning air from NOx using a better, more efficient in terms of NO dissociation: O2 catalyst poisoning ratio catalyst.

In fact, the actual instruments that femtochemistry uses are laser pulses that work after a principle similar to the stroboscope which was about illuminating an event with short pulses of light. That is, in practice, emitting a short pulse that starts the reaction (the pump pulse) and then another one to record the infrared spectra (“take a picture”), the probe pulse.

A consequence of the experiments carried out using this sort of revolutionary technique in observing the behaviour of different metal catalyst with respect to their utility as a surface catalyst for eliminating NOx is that they have lead to finding the explanation for the Ir-Au heterogeneous catalyst not exhibiting the expected behaviour with respect to the NO dissociation/O2 recombination and absorption: addition of very small amounts of Au(±1/10th of an electron) inhibits/promotes the NO dissociation by strengthening/weakening the bond between N and O.

To conclude, understanding the basic mechanisms that dictate the course of essential processes by observing them in real time and under controlled conditions empower the development of advanced, cutting edge technologies improving our everyday life.