The Mudcat Café TM
Thread #59418   Message #2017717
Posted By: Amos
05-Apr-07 - 06:07 PM
Thread Name: BS: The Mother of all BS threads
Subject: RE: BS: The Mother of all BS threads
Hey Ma!! Lissena THIS!!

German-Austrian-Dutch team (Ferenc Krausz, Max Planck Institute of
Quantum Optics and Ludwig Maximilians University Munich, using light pulses lasting only several
hundred attoseconds (billionths of a billionth of a second),
providing new glimpses into an important ultrafast process in
An electron bound to an atom is at the bottom of a sort of energy
hill. Escaping the atom usually requires the electron to get enough
energy to roll over this hill. So for example, hitting an atom with
a light pulse delivering photons of sufficient energy can allow the
electron to escape. However, if an atom is bathed in a shower of
lower-energy photons, there is the chance that an electron, if
located at the periphery of the atom, can escape even though it
doesn't have quite enough energy. This is through the phenomenon of
quantum tunneling, in which there is a small chance that the
electron can in effect burrow through the energy hill. The tunneling
process is responsible for the operation of certain electronic
components, such as scanning tunneling microscopes, Esaki
(tunneling) diodes, and quantum-cascade lasers. And in nuclear
fission, alpha particles (two protons plus two neutrons) are
believed to escape the fracturing nucleus through tunneling. Yet
the tunneling process occurs so quickly, on the scale of
attoseconds, that it has not been possible to observe directly.

With the recent ability to create attosecond-scale light
pulses--pioneered by Krausz and others--this is now possible. In the
new experiment, a gas of neon atoms is exposed to two light pulses.
One is an intense pulse containing low-energy red photons. The
second pulse is an attosecond-length pulse of ultraviolet light.
This ultraviolet attosecond pulse delivers photons so energetic that
they can rip off an electron and promote a second one to the
periphery of the atom, into an excited quantum state. Then, the
intense red pulse, consisting of just a few wave cycles (peaks and
valleys), has a chance to liberate the outlying electron via
light-field-induced tunneling. Indeed, the researchers saw this
phenomenon, predicted theoretically forty years ago but only
verified now for the first time experimentally in a direct
time-resolved study.

As each wave crest in the few-cycle red pulse
coursed through the atoms, the electrons each time upped their
probability of escaping through tunneling until it reached about
100%. The data indicate that, in this particular system, the
electrons escape via tunneling in three discrete steps, synchronized
with the three most intense wave crests at the center of the
few-cycle laser wave. Each step lasts less than 400 attoseconds.
(Uiberacker et al, Nature, 5 April 2007; also see press release with
figures and more information at"

Is that COOL, or WHAT!!!??