Direct Visualization of Barrier Crossing Dynamics in a Driven Optical Matter System

Area of Science:

• Single-molecule dynamics
• Chemical kinetics
• Optical trapping

Background:

• Understanding barrier crossing and single-molecule processes is limited by the inability to directly visualize molecular dynamics.
• Current methods rely on indirect measurements like ensemble kinetics or transducer positions, hindering detailed analysis.

Purpose of the Study:

• To directly measure barrier crossing trajectories and dynamics of single molecules.
• To elucidate the mechanism and driving force dependence of these processes.

Main Methods:

• Utilized optical microscopy to observe position and orientation changes of paired silver nanoparticles in an optical ring trap.
• Analyzed individual trajectories and statistically significant numbers of passing events.

Main Results:

• Achieved direct measurement of barrier crossing trajectories.
• Revealed a two-step mechanism analogous to bimolecular exchange or Michaelis-Menten schemes.
• Found that barrier crossing rate is independent of driving force, attributed to random thermal radial fluctuations.

Conclusions:

• Direct visualization of single-molecule barrier crossing is feasible using optical microscopy and nanoparticle pairs.
• The observed mechanism highlights the role of thermal fluctuations in overcoming energy barriers.
• The experimental approach is adaptable for studying more complex barrier crossing phenomena.