Many dynamical processes in molecules occur in extraordinarily short timescales, of the order of femtoseconds (1 fs = 10^-15 s). In order to follow these processes in real time it is necessary to use the fastest stopwatches available, which are made of ultrashort laser light pulses. In the Center for Ultrashort Lasers (CLUR), in the Complutense University, Madrid, a research team with the participation of Rebeca de Nalda, from IQFR (CSIC), has been taking snapshots of some of these ultrafast processes in molecular systems, while trying to understand the details of the underlying light-matter interaction phenomena.

The new ingredient that has been recently added to these studies is an additional laser pulse that goes beyond the observation of the reaction, and is capable of modifying its course. This pulse is sufficiently intense to alter the molecular potentials, and thus, it causes changes in the products of the reaction and the speeds they acquire in reactions where bonds are broken. This work has been published in Nature Chemistry, and it is a demonstration that the fine control of the properties of this "control" laser pulse turns it into a true "photonic scalpel" capable of manipulating chemical reactions, as well as shedding new light into the dynamics of complex molecular dynamical processes.

M. E. Corrales, J. González-Vázquez, G. Balerdi, I. R. Solá, R. de Nalda, L. Bañares, Control of ultrafast molecular photodissociation by laser field induced potentials, Nature Chemistry (2014), doi:10.1038/nchem.2006