Abstract
AbstractTo explore ultra-fast dynamics in quantum systems one needs detection schemes which allow time measurements in the attosecond regime. During the recent decades, the pump & probe two-pulse laser technique has provided milestone results on ultra-fast dynamics with femto- and attosecond time resolution. Today this technique is applied in many laboratories around the globe, since complete pump & probe systems are commercially available. It is, however, less known or even forgotten that ultra-fast dynamics has been investigated several decades earlier even with zeptosecond resolution in ion-atom collision processes. A few of such historic experiments, are presented here, where the particle motion (due to its very fast velocity) was used as chronometer to determine ultra-short time delays in quantum reaction processes. Finally, an outlook is given when in near future relativistic heavy ion beams are available which allow a novel kind of “pump & probe” experiments on molecular systems with a few zeptosecond resolution. However, such experiments are only feasible if the complete many-particle fragmentation process can be imaged with high momentum resolution by state-of-the-art multi-particle coincidence technique.
Highlights
To explore the nature of atomic matter scientists have developed during the last century sophisticated approaches to reveal the microscopic structure of matter and the dynamics between atoms or even inside atoms and molecules
As will be shown below when dynamical processes proceed via two different pathways they accumulate different phases yielding characteristic interference structures
-called “Pump & Probe” measurements are today commonly identified with Two-pulse Laser Pump & Probe methods where the very short time delay t between the two Laser pulses can be well adjusted by two different geometrical path ways yielding a time resolution in the femto- or even attosecond range
Summary
To explore the nature of atomic matter scientists have developed during the last century sophisticated approaches to reveal the microscopic structure of matter and the dynamics between atoms or even inside atoms and molecules. In fast ion-atom collisions intra-atomic and intra-molecular dynamics can take place even on the lower zeptosecond level (10−19 s), which is about 4 orders of magnitude shorter than the typical femtosecond Laser pulse can resolve [8–12] In such a short time interval light travels only a distance of 0.3 Å. As will be shown below when dynamical processes proceed via two different pathways they accumulate different phases yielding characteristic interference structures From these structures phase differences can be determined and, as outlined before, by knowing the velocity of the fast ion, time delays even in the zeptosecond regime can be deduced [9]. It may be a more theoretical and philosophical issue whether ultra-short time scales below one attosecond may be of any relevance in atomic physics. Is the collapse a non-local process instantaneously present everywhere across the molecule? Measurements with 10 zeptosecond time resolution would allow to explore such a fundamental question e.g. in a triatomic molecule with a non-linear geometry (see Sect. 3.3)
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