Core-level photoemission spectroscopy provides a local probe of expansion dynamics and associated transient chemical properties as a highly pressurized, metallic fluid expands into vacuum following impulsive heating of a semiconductor by an intense, ultrashort laser pulse. Transient photoemission peak shifts reveal that metal-insulator transitions occur rapidly following laser heating. These experiments probe constituents species and solidification kinetics occurring in the early moments of material ejection and provide insight into how particles arise in the current laser ablation regime.