Prechemical

From this time until about 10−12 s, in the prechemical phase, some initial reactions and rearrangements of these species occur.

Source: wiktionary

But much remains to be done in understanding the complex physical, prechemical and chemical stages of radiation interactions in even the simplest, biologically relevant, condensed materials.

Source: wiktionary

An implication of this rationale is that a "prechemical" electron transfer occurs prior to the initiating step of carcinogen-biotarget interaction, which can culminate in adduct formation, intercalation, alkylation, etc. […]

Source: wiktionary