We present an experimental study on the fragmentation dynamics of sulfur dioxide (SO2) under femtosecond laser irradiation. Using the fragment ions coincidence momentum imaging technique, two two-body and one three-body fragmentation channels of SO22+ are analyzed. For the three-body channel, four different dissociation mechanisms are determined unambiguously by analyzing the kinetic energy and momentum correlations, Dalitz plots, and the native frame maps. In addition to the concerted and conventional sequential fragmentation paths, a novel three-body fragmentation pathway, defined as an isomerization pathway, was identified, in which a rapidly rotating O2+ molecular ion is formed prior to fragmentation into individual fragments. This new fragmentation mechanism may provide new insights to explain the abiotic oxygen production in SO2-dominated planetary atmospheres.
Dong et al. (2026) studied this question.