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Wing-Ki Liu
Present Research Activities
Laser-molecule interactions
We study theoretically the photodissociation of diatomic molecules
using both classical and quantum mechanics.
We have provided a clear physical picture, called
bucket dynamics,
to explain the efficiency of photoexcitation by
chirped infrared laser pulses, and
we are investigating the coherent control of molecular excitation by chirped
lasers.
We also study the classical dynamics of strong field ionization and
dissociation of simple molecules
without making the Born-Oppenheimer
approximation so that both the electronic and nuclear motions are
treated on equal footing. We are considering the classical
calculation of high harmonic
generation spectra, and the classical-quantum correspondence.
Molecular collision
Nonlinear optical studies of gaseous systems such as coherent Raman
spectroscopy, collision-induced fluorescence, two-photon double resonance, and
pump-probe experiments can yield valuable information about the
underlying collision dynamics, which can be described by
various generalized cross sections (GCS). These GCS's are
determined by the intermolecular forces between atoms and
molecules of the systems under study. We have an ongoing program
of performing quantum mechanical, semiclassical, and classical
calculations of the GCS's and comparing with experiments to extract
information about the intermolecular potentials.
Particle-surface interactions
Recently we have studied the energy loss of atomic ions or clusters moving
near solid surfaces and inside the solid
using the response function formalism for
the solid substrate. We are extending our studies to investigate
the dissociation of molecular ions and the dynamics of Coulomb explosions.
We are also studying the infrared and sum frequency generation spectra of
atoms and molecules dsorbed on surfaces, and we are planning to
use molecular dynamics techniques to study adsorbate-surface
interactions.
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