Details

Autor(en) / Beteiligte

• Eckle, P
• Pfeiffer, A.N
• Cirelli, C
• Staudte, A
• Dörner, R
• Muller, H.G
• Büttiker, M
• Keller, U

Titel

Attosecond Ionization and Tunneling Delay Time Measurements in Helium

Ist Teil von

• Science (American Association for the Advancement of Science), 2008-12, Vol.322 (5907), p.1525-1529

Ort / Verlag

Washington, DC: American Association for the Advancement of Science

Erscheinungsjahr

2008

Quelle

Science Magazine

Beschreibungen/Notizen

• It is well established that electrons can escape from atoms through tunneling under the influence of strong laser fields, but the timing of the process has been controversial and far too rapid to probe in detail. We used attosecond angular streaking to place an upper limit of 34 attoseconds and an intensity-averaged upper limit of 12 attoseconds on the tunneling delay time in strong field ionization of a helium atom. The ionization field derives from 5.5-femtosecond-long near-infrared laser pulses with peak intensities ranging from 2.3 x 10¹⁴ to 3.5 x 10¹⁴ watts per square centimeter (corresponding to a Keldysh parameter variation from 1.45 to 1.17, associated with the onset of efficient tunneling). The technique relies on establishing an absolute reference point in the laboratory frame by elliptical polarization of the laser pulse, from which field-induced momentum shifts of the emergent electron can be assigned to a temporal delay on the basis of the known oscillation of the field vector.