Interatomic relaxation effects in double core ionization of chain molecules

Area of Science:

• Quantum Chemistry
• Molecular Physics
• Spectroscopy

Background:

• Core vacancies in molecules lead to relaxation effects.
• Simultaneous creation of two core holes results in reduced relaxation energy compared to individual holes.
• Interatomic relaxation energy is sensitive to the molecular environment.

Purpose of the Study:

• To investigate the dependence of interatomic relaxation energy on the length and type of carbon chains bridging two core-ionized nitrile groups.
• To understand the influence of carbon hybridization and molecular bridge energetics on interatomic relaxation.

Main Methods:

• Theoretical exploration using electrostatic and quantum mechanical models.
• Analysis of trends in interatomic relaxation energy based on molecular structure.

Main Results:

• Absolute interatomic relaxation energy is larger in conjugated carbon chains (sp, sp(2) hybridization) than in saturated chains (sp(3) hybridization).
• Interatomic relaxation energy decreases monotonically with increasing carbon chain length.
• The HOMO-LUMO gap of the molecular bridge influences the rate of decrease; sp(2)-hybridized backbones show the slowest decrease.

Conclusions:

• Orbital hybridization and chain length are critical factors determining interatomic relaxation energy.
• Conjugated systems with delocalized π-orbitals exhibit stronger interatomic relaxation effects.
• The HOMO-LUMO gap plays a key role in modulating the distance dependence of interatomic relaxation.