Laser Setup Proposed for Attosecond Spectroscopy

A research team at the University of Ottawa and at Steacie Institute of Molecular Sciences, both in Ottawa, has proposed a laser configuration that may enable scientists to probe attosecond-long nuclear phenomena. The approach was described in the Jan. 9 issue of Physical Review Letters.

When an intense laser pulse interacts with matter, the pulse ionizes the atom or molecule, accelerates the freed electron and drives it back toward the ion for recollisions. The duration of the recolliding electron wave packet is in the attosecond regime. In the case of a single propagating laser pulse, the magnetic field of the pulse -- the Lorentz force -- limits the energy of the returning electron to less than 1 keV.

The researchers calculate that using two counterpropagating laser pulses that are circularly polarized and equally handed, rather than a single pulse, eliminates the Lorentz force that prevents recollisions for laser intensities greater than 10¹⁶ W/cm². The ability to employ more intense laser pulses -- on the order of 10²³ W/cm² -- using the new setup should yield electron recollisions at energies greater than 1 MeV. Together with the attosecond duration of the electron wave packet, this should enable the time-resolved study of attosecond nuclear dynamics.