A semiclassical study of wave packet dynamics in anharmonic potentials

Area of Science:

• Quantum Dynamics
• Spectroscopy
• Computational Chemistry

Background:

• Pump-probe spectroscopy measures ultrafast molecular dynamics.
• Classical methods often fail to capture quantum interference effects.
• Accurate theoretical models are needed to interpret experimental data.

Purpose of the Study:

• Develop and validate classical and semiclassical methods for analyzing wave packet motion in pump-probe experiments.
• Relate temporal signal features to potential surface characteristics.
• Incorporate quantum interference into classical trajectory calculations.

Main Methods:

• Classical propagation of the Wigner distribution.
• First-order canonical perturbation theory.
• Final-value representation semiclassical method.
• Phase-space quantization scheme for one-color pump-probe signals.

Main Results:

• Classical propagation predicts approximate signals with displaced recurrence peaks.
• Reduced dynamics based on Gaussian assumption captures center-of-mass motion but not wave packet shape evolution.
• The proposed semiclassical method accurately computes pump-probe signals for Morse oscillators.
• Phase-space quantization reproduces temporal profiles without full wave packet propagation.

Conclusions:

• Semiclassical methods, particularly the final-value representation, are efficient and accurate for pump-probe signal computation.
• These methods provide insights into quantum mechanical aspects of nearly classical pump-probe signals.
• The developed techniques enhance the interpretation of experimental ultrafast molecular dynamics data.