
April 25, 2014 11:1 PSP Book - 9in x 6in 06-Rashid-A.-Ganeev-c06
High-Order Harmonic Cutoff Frequency in Atomic Silver Irradiated 211
where
ω
pα
(
e
)
=
4πe
2
N
α
(
e
)
mV
is the plasma frequency corresponding to neutral atoms (α = I ),
ions (α = II), and free electrons (e); N
α
is the number of neutral
atoms and ions in the irradiated volume V ,andN
e
is the number of
free electrons. When neutral and ionized atoms stay mainly in the
ground state, we can assume that ω
0I
(
II
)
are the binding energies
of a silver atom (α = I ) and ion (α = II), respectively. In the
case of ultrashort laser pulses, the relaxation rates γ
α
(
e
)
are inversely
proportional to the laser pulse tempor ...