Elementary motions of atoms and molecules can be observed with femtosecond lasers. By contrast, electron dynamics that determines dynamics of atoms and molecules often occurs on attosecond timescales (1 as = 10-18s). Very recently first attosecond laser pulses were obtained by high-harmonic generation. In this process continuum electrons are formed by ionisation of a noble-gas atom with an intense laser field and accelerated to energies of over 100 eves. Extreme ultraviolet (XUV) photons can be generated upon re-collision and recapture of the electron into the ground state of the atom. The XUV photons are generated within a small fraction of the driving laser cycle (2.7 fess at 800 nm) leading to attosecond light bursts as short as 250 as. So far, it is predominately the formation of a train of attosecond laser pulses that has been observed. The aim of this proposal is to produce and characterize single attosecond laser pulses, allowing measurements at unprecedented time resolution. The production of single attosecond laser pulses requires ultra short (sub-10 femtosecond) driver pulses, which we will realize by modification of the AMOLF Terawatt- laser system. Another important issue, which is also addressed in this proposal, is the full characterization of single attosecond laser pulses using a new diagnostic technique. In order to gain further insight into the electron dynamics during the harmonic generation process (ionisation and recombination following acceleration in the laser field), complementary experiments will be undertaken on picot- and nanosecond time-scales with The- and MHz-radiation. Using The- and MHz-radiation and initial preparation of the atoms in a high Ryder state, we will monitor the motion of the electron wave packet and the time distribution of its return to the ion (being the key to the generation of the attosecond pulses!) in real-time and potentially improve upon, pointing the way to improved attosecond pulse generation.
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