Factors governing formation from methyl halogens and pseudohalogens

Area of Science:

• Physical Chemistry
• Chemical Physics
• Astrochemistry

Background:

• The roaming mechanism in small organic compounds following double ionization, involving H2 generation and proton abstraction, is of recent interest.
• A unified model explaining the yield trends of specific molecular ions in these unimolecular reactions is currently lacking.

Purpose of the Study:

• To establish a cohesive model for the yield of specific molecular ions formed via roaming mechanisms in doubly ionized small organic molecules.
• To identify key factors influencing the formation and absence of these ions in various CH3X species.

Main Methods:

• Femtosecond time-resolved measurements of strong-field double ionization in CH3X molecules (X = OD, Cl, NCS, CN, SCN, I).
• Ab initio calculations, including double-ionization-potential equation-of-motion coupled-cluster, to determine dication geometries and energetics.
• Ab initio molecular dynamics simulations for microscopic insights into the mechanism, yields, and timescales of ion production.

Main Results:

• Identified key factors governing the formation of specific molecular ions in doubly ionized CH3X species.
• Demonstrated that excess relaxation energy and geometrical distortions favoring H2 formation enhance ion generation.
• Provided detailed microscopic insights into the mechanism, yields, and timescales of ion production.

Conclusions:

• Excess relaxation energy and favorable structural distortions post-double ionization are crucial for boosting specific molecular ion formation.
• The study offers guidelines for investigating alternative extraterrestrial sources of these ions.
• A deeper understanding of unimolecular reactions in doubly ionized organic molecules is achieved.