Controlling vibrational excitations in C60 by laser pulse durations

Area of Science:

• Physical Chemistry
• Materials Science
• Computational Physics

Background:

• Conflicting experimental results exist regarding dominant vibrational modes (A(g) vs. H(g)) in C60 relaxation after ultrafast laser excitation.
• Understanding these relaxation pathways is crucial for controlling molecular dynamics.

Purpose of the Study:

• To systematically investigate the influence of ultrafast laser pulse duration on vibrational mode selectivity in C60.
• To resolve the discrepancy between experimental findings on dominant relaxation modes.

Main Methods:

• Systematic computational simulations of off-resonant ultrafast laser experiments in C60.
• Numerical analysis of vibrational mode dominance as a function of laser pulse duration.
• Construction of a comprehensive excitation diagram based on laser frequency and pulse duration scans.

Main Results:

• The discrepancy in experimental results is attributed to variations in laser pulse duration.
• Each vibrational mode (nu) exhibits a distinct optimal pulse duration (tau(nu)(o)).
• A(g) modes are suppressed for pulse durations > 40 fs, while H(g) modes become dominant.
• A relationship Omega(o)(nu)/tau(nu)(o) ≈ 3.4 was found for dominant modes under specific excitation conditions.

Conclusions:

• Laser pulse duration is a critical parameter for selectively controlling vibrational relaxation pathways in C60.
• The developed excitation diagram provides experimental guidance for targeting specific A(g) or H(g) modes.
• This work offers a pathway to precisely manipulate molecular dynamics in C60 using ultrafast lasers.