Reaching the Attosecond Range

One of these techniques is based on the generation of high harmonics of a powerful femtosecond laser pulse [746]. 

The minimum time duration of a pulse with the carrier frequency v = c/A. is 

For X = 700 nm this gives AT = 2.3 x 10 s = 2.3 fs. In order to realize pulses in the attosecond range (I as = 10 s) one has to choose shorter wavelengths. This can be achieved by generation of high harmonics. For the 50th harmonics at A. = 14 nm one obtains already a lower limit for the pulse width of AT = 46 as. 

To illustrate atomic dynamics, which require subfemtosecond resolution. Fig. 6.58 shows the time-resolved field ionization of neon atoms in the optical field of a 5 fs laser pulse which consists of only three optical cycles within the pulse half width [750]. The whole process proceeds within about 6 fs, but one can clearly see peaks in the ionization probability at times of maxima in the optical field, which means that the time resolution is below 1 fs. 

Such femto- to attosecond X-ray pulses can be used for the generation of Laue diagrams of vibrational or electronical excited molecules. The exposure time must 

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