In this perspective we describe a 15 year pursuit of the Stabilized Criegee Intermediate (SCI). We have conducted several complementary experiments to measure the pressure dependence of product yields-including OH radical and ozonides-on sequences of alkene + ozone systems. In so doing we have been able to bring into gradual focus a succession of weakly bound intermediates, starting with the primary ozonide, then the SCI, and finally a vinyl hydroperoxide (VHP) product of SCI rearrangement. We have narrowed the phase space in our hunt for direct SCI observations to a range of alkene carbon numbers and system pressures, but the system continues to deliver surprises. One surprise is strong evidence that the VHP is a significant bottleneck along the reaction coordinate. These findings support the search for the SCI, build our fundamental understanding of collisional energy transfer in highly excited, multiple-well, chemically activated systems, and finally directly inform atmospheric chemistry on topics including HO_x radical formation and reactions associated with secondary organic aerosol formation.
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