Probing Chemical Reactions: Evidence for Exploration of an Excited Potential Energy Surface at Thermal Energies

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Science  10 Sep 1993:
Vol. 261, Issue 5127, pp. 1434-1436
DOI: 10.1126/science.261.5127.1434


The reaction K + NaBr → KBr + Na is probed during the reactive collision by a continuous wave laser tuned to frequencies not resonant with excitation in either reagents or products. Transient [K..Br..Na] absorbs a laser photon giving [K..Br..Na]*, which can decompose to Na* + KBr. Emission from excited Na* at the sodium D lines provides direct evidence of laser absorption during the reaction. Different excitation spectra were observed, depending on which sodium D line was monitored. This difference is explicable if, in the absence of the laser, the reaction flux partially bifurcates to a second potential energy surface during the reaction.