Conformer-Specific Dissociation Dynamics in Dimethyl Methylphosphonate Radical Cation

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Dimethyl methylphosphonate (DMMP) is a molecule of interest for understanding chemical dynamics.
• Strong field ionization techniques provide a route to study molecular cations.
• Investigating cation dynamics is crucial for understanding chemical reactions and molecular behavior.

Purpose of the Study:

• To investigate the ultrafast dynamics of the dimethyl methylphosphonate (DMMP) radical cation.
• To explore the fragmentation pathways of DMMP cation conformers using pump-probe spectroscopy.
• To elucidate the role of electronic excitation in cation dissociation.

Main Methods:

• Pump-probe spectroscopy with 1300 nm ionization and 800 nm probe pulses.
• Adiabatic ionization to produce DMMP radical cations.
• Electronic structure theory and nonadiabatic surface hopping dynamics simulations.

Main Results:

• Coherent oscillations in parent ion yield with a ~45 fs period were observed.
• Fragment ion yields oscillated out of phase with the parent ion, indicating complex dynamics.
• Computational and experimental data suggest conformer-specific dissociation pathways after electronic excitation.

Conclusions:

• DMMP cation dynamics involve oscillations on the ground electronic state and excitation to higher states leading to fragmentation.
• Conformational differences in DMMP influence cation dynamics and subsequent dissociation.
• Pump-probe spectroscopy is a valuable tool for studying conformer-specific dynamics in molecules.