Increasing the electronic temperature by laser pulses leads to a weakening of the O-Ru bond which allows  reaction to CO₂ take place by lowering the energy activation barrier.

O-Ru bond weakening due to partially occupying a previously unoccupied antibonding orbital through laser-induced increase in the electronic temperature. [M. Bonn, S. Funk, Ch. Hess, D.N. Denzler, C. Stampfl, M. Scheffler, M. Wolf, and G. Ertl, Science 285, 1042 (1999)]