Factors governing formation from methyl halogens and pseudohalogens.

The formation of following the double ionization of small organic compounds via a roaming mechanism, which involves the generation of H and subsequent proton abstraction, has recently garnered significant attention. Nonetheless, a cohesive model explaining trends in the yield of characterizing these unimolecular reactions is yet to be established. We report yield and femtosecond time-resolved measurements following the strong-field double ionization of CHX molecules, where X = OD, Cl, NCS, CN, SCN, and I. These measurements, combined with double-ionization-potential equation-of-motion coupled-cluster ab initio calculations used to determine the geometries and energetics of CHX dications, are employed to identify the key factors governing the formation of in certain doubly ionized CHX species and its absence in others. We also carry out ab initio molecular dynamics simulations to obtain detailed microscopic insights into the mechanism, yields, and timescales of production. We find that the excess relaxation energy released after double ionization of CHX molecules combined with substantial geometrical distortion that favors H formation prior to proton abstraction boost the generation of . Our study provides useful guidelines for examining alternative sources of in the universe.