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October 06, 2009

Attoseconds, Zeptoseconds and Yoctoseconds

Attoseconds are 10^-18 seconds. 1 attosecond is the time it takes for light to travel the length of three hydrogen atoms.
Zeptoseconds are 10^-21 seconds
Yoctoseconds are 10^-24 seconds. 1 ys: time taken for a quark to emit a gluon. The time that light needs to traverse an atomic nucleus

1.
Collisions of heavy ions in a large accelerator facility (schematic). Under certain conditions, double light flashes of a few yoctoseconds duration can be emitted. MPI for Nuclear Physics

Yoctosecond Photon Pulses from Quark-Gluon Plasmas

Present ultrafast laser optics is at the frontier between atto- and zeptosecond photon pulses, giving rise to unprecedented applications. We show that high-energetic photon pulses down to the yoctosecond time scale can be produced in heavy-ion collisions. We focus on photons produced during the initial phase of the expanding quark-gluon plasma. We study how the time evolution and properties of the plasma may influence the duration and shape of the photon pulse. Prospects for achieving double-peak structures suitable for pump-probe experiments at the yoctosecond time scale are discussed.

High-energy heavy ion collisions, which are studied at RHIC in Brookhaven and soon at the LHC in Geneva, can be a source of light flashes of a few yoctoseconds duration (a septillionth of a second, 10-24 s, ys) - the time that light needs to traverse an atomic nucleus. This is shown in calculations of the light emission of so-called quark-gluon plasmas, which are created in such collisions for extremely short periods of time. Under certain conditions, double flashes are created, which could be utilized in the future to visualize the dynamics of atomic nuclei.

In the collision of heavy ions (i.e. atoms of heavy elements from which all electrons have been removed) at relativistic velocities, such a quark-gluon plasma is created for a few yoctoseconds at the size of a nucleus. Among many other particles, it also creates photons of a few GeV (billion electron volts) energy, so-called gamma radiation. These high-energy flashes of light are as short as the lifetime the quark-gluon plasma and consist of only a few photons.



Temporal evolution of the quark-gluon plasma. Two ions (colored disks) collide along the beam collision axis (black double arrow). Image (a) shows the time immediately after the collision. The plasma (orange area) shines light (wavy arrows) in all directions, so that a first pulse in the direction of the detector (green semi-circle) is formed. (b) After some time, the inner dynamics of the plasma will cause light to be preferentially radiated perpendicular to the direction of flight of the ions. During this time no light is emitted into the direction of the detector which is placed close to the collision axis. In (c) the plasma radiates again in all directions, so that the second pulse is emitted in the direction of the detector.
MPI for Nuclear Physics


2. ADVANCED SPECTROSCOPY: Attosecond spectroscopy moves beyond the atomic scale

Ultrashort attosecond light pulses, when used as the "shutter" in an imaging or spectroscopy system, can probe into the attosecond realm to see how the actual motions of electrons drive atomic and molecular dynamics.

The application of these 80 as pulses to the field of spectroscopy is vast. "For example, in life sciences attosecond spectroscopy may ultimately create ways of understanding the microscopic origins of how a disease, such as cancer, emerges and develops at the most fundamental level: in terms of the motion of electrons," said Ferenc Krausz, director of MPQ, head of the Attosecond and High Field Physics division of MPQ, and pioneer of femto­second and attosecond science.

To create an attosecond light pulse, a phase-stabilized femtosecond laser with pulse-to-pulse uniformity in terms of intensity, frequency, and physical shape are input to a gas jet such as neon. The femtosecond pulse pulls electrons from the neon atoms (field ionization), which then collide with their "parent" atoms in a recombination process and produce a synchronized, attosecond duration, extreme ultraviolet (XUV) pulse in a high-order harmonic generation (HHG) process


Further shortening light pulses would enable even more new scientific ground to be explored. “Pulses in the so called zeptosecond time scale (1 zeptosecond is 10–21 seconds) might also become available in the future,” says Goulielmakis. “This timescale is relevant to the proton and neutron motion inside the nuclei of atoms and therefore will open the door to capturing nuclear processes in real time.”



3. Laser gate: multi-MeV electron acceleration and zeptosecond e-bunching

Relativistically-intense laser beam with large field gradient (”laser gate”) enables strong inelastic scattering of electrons crossing the beam. This process allows for multi-MeV electron net acceleration per pass within the wavelength space. Inelastic scattering even in low-gradient laser field may also induce extremely tight temporal focusing and electron bunch formation down to quantum, zepto-second limit.



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