Fundamental
Investigation of Intense Laser-Molecule Interactions
The
interaction of intense, short pulse lasers with polyatomic molecules presents
a new area of research for the chemical physicist. The laser pulse
has sufficient intensity that essentially any molecule will be excited
with up to 50 eV of energy, but the pulse duration is short enough that
the energy need not channel into the nuclear modes resulting in substantial
decomposition. Using longer duration laser pulses of similar intensities
results in decomposition to ionized atomic fragments. We demonstrated
in 1995 that in fact intact ionization can be obtained for large polyatomic
molecules at intensities above 1013 W cm-2 with short
duration laser pulses. To begin to understand the strong field interaction
we have performed a number of experiments measuring the photoelectron spectra,
the mass spectra and the ion kinetic energy distributions for many series
of molecules. A key theoretical advance for understanding the measurment
was the development of the structure-based model by this group in the late
1990's. More information regarding our fundamental investigation
can be found in the following papers:
1: Robert
J. Levis and Merrick J. DeWitt, "Photoexcitation,
Ionization and Dissociation of Molecules Using Intense Near-Infrared Radiation
of Femtosecond Duration ," J. Phys.
Chem. A 103(33): 6493-6507, 1999
2: Alexei
N. Markevitch, Noel P. Moore and Robert J. Levis,
"The Influence of Molecular Structure
on Strong Field Energy Coupling and Partitioning,"Chem.
Phys.,
267(1-3), 131-140, 2001
3: Noel
P. Moore and Robert J. Levis, "The
Strong Field Photoelectron Spectroscopy of Acetylene: Evidence for Short-Lived
4p Gerade States Via Electric Field-Induced REMPI" J.
Chem. Phys. 112(3): 1316-1320, 2000
4: M.J.
DeWitt and R.J. Levis, "Observing
the Transition From Multiphoton-Dominated to Field-Mediated Ionization
Process for Polyatomic Molecules in Intense Laser Fields," Phys.
Rev. Lett. 81(23): 5101-5104 DEC 7, 1998
