Lecture by the 2016 Honorary Doctor at Science and Technology, AU - Paul Corkum

Aud I (1514-213) 8. september 2016 kl. 15.15 (Vært: Henrik Stapelfeldt)

25.08.2016 | Pernille Pia Krintel

Paul Corkum

Speaker:
2016 Honorary Doctor Paul Corkum Joint Attosecond Science Lab University of Ottawa and National Research Council of Canada

Title:
Probing quantum systems from the inside – on the attosecond time scale

 

Abstract:

Attosecond pulses are generated by electrons that are extracted from a quantum system by tunneling in an intense light pulse and travel through the continuum. Portions of each electron wave packet are forced to re-collide with its parent ion by the oscillating force of the time dependent electric field from the light pulse. Upon re-collision, the electron and ion can recombine, emitting VUV or soft X-ray radiation. Since nonlinear optics underlies every ultrafast pulse that we create and every ultrafast measurement that we perform in chemistry, physics or biology, a new nonlinear process is bound to be important. If we ensure that the intense driving pulse only permits re-collision within a fraction of a light period, in rare gas atoms re-collision generates the world’s shortest pulses (currently ~ 65 x 10-18 sec). If we use a mid-infrared driver pulse, it can also generate coherent soft X-ray radiation by combining 1000s of infrared photons into one with photon energy > 1 keV. But the re-collision electron, with wavelength in the 3-0.3 Ångstrøm range, is also a probe of structure. In semiconductors we can measure the band structure of the material in which the process occurs. Band structure information is encoded in the emitted light – effectively an inverse photoelectron spectroscopy. Using small molecules, the emitted spectrum contains the information needed to image the structure of the wave function of the orbital (or orbitals) from which the re-collision electron was taken. As time permits the talk will cover these issues. Attosecond pulses are generated by electrons that are extracted from a quantum system by tunneling in an intense light pulse and travel through the continuum. Portions of each electron wave packet are forced to re-collide with its parent ion by the oscillating force of the time dependent electric field from the light pulse. Upon re-collision, the electron and ion can recombine, emitting VUV or soft X-ray radiation. Since nonlinear optics underlies every ultrafast pulse that we create and every ultrafast measurement that we perform in chemistry, physics or biology, a new nonlinear process is bound to be important. If we ensure that the intense driving pulse only permits re-collision within a fraction of a light period, in rare gas atoms re-collision generates the world’s shortest pulses (currently ~ 65 x 10-18 sec). If we use a mid-infrared driver pulse, it can also generate coherent soft X-ray radiation by combining 1000s of infrared photons into one with photon energy > 1 keV. But the re-collision electron, with wavelength in the 3-0.3 Ångstrøm range, is also a probe of structure. In semiconductors we can measure the band structure of the material in which the process occurs. Band structure information is encoded in the emitted light – effectively an inverse photoelectron spectroscopy. Using small molecules, the emitted spectrum contains the information needed to image the structure of the wave function of the orbital (or orbitals) from which the re-collision electron was taken. As time permits the talk will cover these issues.

Coffee in the foyer at 15:00

 

 

Institut for Kemi, Offentligheden / Pressen, Medarbejdere