Attosecond timescale

Because electrons are much lighter than nuclei, they move much faster. The intrinsic temporal regime for valence bond electron dynamics is the few femtosecond to several hundred attosecond timescale. Therefore, efficient and accurate control of electron dynamics requires extreme precision regarding the control field. Commonly attosecond techniques are considered to be the appropriate tools for efficient manipulation of electron motions [61-63, 111, 112]. However, attosecond pulses in the XUV region are not suited for efficient valence bond excitation (see Section 6.1). Here we demonstrate that ultrafast electron dynamics are controlled efficiently on the sub-10 as timescale employing a pair of femtosecond laser pulses with a temporal separation controllable down to zeptosecond precision [8]. 

E. Foumouo, P. Antoine, H. Bachau, B. Piraux, Attosecond timescale analysis of the dynamics of two-photon double ionization of helium, New J. Phys. 10 (2008) 025017. 

We start our discussion of laser-controlled electron dynamics in an intuitive classical picture. Reminiscent of the Lorentz model [90, 91], which describes the electron dynamics with respect to the nuclei of a molecule as simple harmonic oscillations, we consider the electron system bound to the nuclei as a classical harmonic oscillator of resonance frequency co. Because the energies ha>r of electronic resonances in molecules are typically of the order 1-10 eV, the natural timescale of the electron dynamics is a few femtoseconds to several hundred attoseconds. The oscillator is driven by a linearly polarized shaped femtosecond... 

In ultrafast laser science the emergence of attosecond laser pulses raises the prospect of studying electronic wavepacket motion on the natural timescales of this motion in nature, namely the atomic unit of time (1 a.u. = 24 attosec-onds = 0.024 femtoseconds) [1,2]. Attosecond science may have a profound impact on the way we understand photo-induced physical and chemical processes. 

After several decades of highly succesful experimentation with femtosecond lasers that has allowed unravelling of atomic motion on femtosecond timescales, the recent development of attosecond techniques represents the starting point for efforts to study the motion of electrons in real time. The outcome of this effort will not be known for a number of years, but the astonishing progress that has been made in the last few years suggests that we may be very optimistic about the rewards from attosecond experiments yet... 

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