Threshold collision induced dissociation of pyrene cluster cations

Area of Science:

• Physical Chemistry
• Chemical Physics
• Materials Science

Background:

• Cationic pyrene clusters are studied to understand their stability and fragmentation.
• Charge resonance is a theoretical concept predicting enhanced stability in such clusters.
• Previous studies used thermal evaporation to estimate dissociation energies.

Purpose of the Study:

• To experimentally determine dissociation energies of cationic pyrene clusters (n=2-6).
• To validate theoretical predictions of charge resonance stability enhancement.
• To compare experimental results with theoretical calculations and thermal evaporation data.

Main Methods:

• Threshold collision-induced dissociation (CID) experiments were performed on cationic pyrene clusters.
• Fragmentation cross sections were measured as a function of collision energy.
• A statistical model was employed to analyze dissociation cascades and derive dissociation energies.

Main Results:

• Experimental dissociation energies (0.7-1 eV) closely match thermal evaporation data.
• Results confirm the charge resonance stability enhancement predicted by theory.
• Good agreement with theoretical predictions for n=2 and 3; a systematic 0.2 eV offset for larger clusters.
• Evidence suggests potential underestimation of isomerization/direct dissociation roles in theory.

Conclusions:

• The study validates the use of CID and statistical modeling for determining cluster dissociation energies.
• Experimental findings support the theoretical concept of charge resonance enhancing cationic pyrene cluster stability.
• Discrepancies in larger clusters may stem from theoretical approximations or overlooked dissociation pathways.