Mj. Dewitt et Rj. Levis, CALCULATING THE KELDYSH ADIABATICITY PARAMETER FOR ATOMIC, DIATOMIC, AND POLYATOMIC-MOLECULES, The Journal of chemical physics, 108(18), 1998, pp. 7739-7742
A numerical model is presented to determine the Keldysh adiabaticity p
arameter for the interaction of an intense laser with a polyatomic mol
ecule. The adiabaticity parameter is a guide to determining whether th
e ionization process is in the field or multiphoton ionization regime.
The adiabaticity parameters are compared for potentials including the
simple zero-range potential, the Coulomb potential, an atomic potenti
al (Xe), a diatomic (N-2) molecular potential, and a polyatomic (C6H6)
molecular potential. It is demonstrated that the Coulomb potential is
approximately equal to the atomic and diatomic potentials and differs
from the zero-range potential employed in the Keldysh model in a way
which is predominantly dependent upon the ionization potential. Both s
imple models substantially overestimate the adiabaticity parameter for
C6H6 at all field strengths and at fields above 1.25 V/Angstrom both
simple models become completely unphysical. This is because barrier su
ppression ionization is predicted to occur for benzene above 1.25 V/An
gstrom using the ab initio potential. This field for barrier suppressi
on ionization is significantly lower than the 1.5 V/Angstrom field pre
dicted using the Coulomb model. (C) 1998 American Institute of Physics
.