Structure, Reactivity, and Fragmentation of Small Multi-Charged Methane Clusters.

Area of Science:

• Physical Chemistry
• Chemical Physics
• Laser Physics

Background:

• Methane clusters exhibit complex behavior under high-energy conditions.
• Understanding cluster dynamics is crucial for various chemical and physical processes.

Purpose of the Study:

• To investigate the fragmentation and reaction pathways of small methane clusters (CH4)n upon intense femtosecond laser excitation.
• To characterize the resulting ionized species and their subsequent reactions.

Main Methods:

• Irradiation of small methane clusters with intense femtosecond laser pulses at 624 nm.
• Detection of ionized and fragmented species using time-of-flight mass spectrometry (TOF MS).
• First-principles calculations ( (R)MP2/aug-cc-pVXZ) for spectral assignment and stability analysis of charged clusters (n=1-4, q=1-4).

Main Results:

• Evidence for bound, multiply charged methane molecules and clusters formed via Coulomb explosion.
• Identification of unique intracluster reactions and fragmentation patterns in multiply charged small methane clusters.
• Calculations confirmed cluster stabilities and potential fragments from intracluster reactivity.

Conclusions:

• Multiply charged small methane clusters exhibit distinct intracluster reaction and fragmentation dynamics.
• These dynamics differ from those of isolated methane ions and large ionized methane clusters.
• Femtosecond laser excitation provides insights into ultrafast processes in molecular clusters.