Selective bond-breaking in formic acid by dissociative electron attachment.

Area of Science:

• Physical Chemistry
• Chemical Physics
• Atomic and Molecular Physics

Background:

• Dissociative electron attachment (DEA) is a key process in understanding molecular fragmentation.
• Formic acid (HCOOH) is a fundamental molecule with significant implications in various chemical environments.
• Investigating DEA to HCOOH provides insights into fundamental electron-molecule interactions and bond cleavage dynamics.

Purpose of the Study:

• To investigate the mechanisms of H- fragment ion formation during DEA to formic acid in the 6-9 eV energy range.
• To differentiate between C-H and O-H bond scission pathways using isotopic substitution.
• To elucidate the role of Feshbach resonances in the dissociation of formic acid.

Main Methods:

• Joint experimental and theoretical study of dissociative electron attachment.
• Experimental measurements utilizing deuteration of formic acid at either the C-H or O-H site.
• Theoretical calculations of Feshbach resonance states and their dissociation dynamics.
• Analysis of anion fragment angular distributions.

Main Results:

• Hydrogen anions (H-) are identified as dominant products in the 6-9 eV region.
• Two or possibly three Feshbach resonance states contribute to H- formation.
• One resonance state leads to C-H or O-H bond scission, while another exclusively produces formyloxyl radicals via O-H bond scission.
• Experimental and theoretical angular distributions confirm state-specific dissociation pathways.

Conclusions:

• The study successfully distinguishes between C-H and O-H bond breaking in formic acid via DEA.
• Feshbach resonances play a critical role in directing the fragmentation pathways.
• Detailed understanding of electron-induced bond cleavage in small molecules is advanced.