Beyond Death Valley: Dressed Electrons


In pushing the laser intensity higher at fixed frequencies, the Rochester group made its unexpected discovery. Their simulations showed that, up to a point, as laser intensity increases so does the likelihood that the electron will be ionized. Past that critical point, however -- contrary to expectation -- the electron's chances of survival in the atom begin to improve. The region where this reversal occurs, where electron survival is shortest, is known in strong-field physics as "Death Valley."

In the laser-stabilized state, on the other side of Death Valley, the electron is referred to as being "fully dressed" by the laser field, in a sense a change of costume that changes behavior. At these very high intensities, the laser captures the electron in the field of its wave, shaking it back and forth with wavelike vibrations. "In a way," says Eberly, "we've come full circle, and we find with these super-intense lasers that we're back to the situation Einstein overthrew -- that the wave picture of light is more appropriate."

The other side of Death Valley is also new territory in the sense that, for the first time in this field, experiments by computer are making discoveries ahead of experiments by laser. Laser experiments are underway in labs worldwide to confirm Eberly's and Kulander's computational results.

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