University of Connecticut

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Atomic, Molecular, And Optical Physics Seminar

Wednesday, February 24, 2021
4:00pm – 5:00pm

Storrs Campus

Dr. Jean Marcel Ngoko Djiokap, Department of Physics & Astronomy, University of Nebraska, Lincoln

Control of Electron Motion on an Attosecond Timescale

Technological advances 20 years ago in producing new extreme ultraviolet coherent light sources with attosecond duration have created a new research field, namely, attosecond physics. A main goal of attosecond physics is to control electron motion on its natural (attosecond) timescale, in order to probe bond formation and breaking in molecules during chemical reactions. A milestone toward achieving such goal is the experimental realization of isolated, few-cycle, attosecond pulses seeded by a free electron laser (FEL) or high harmonic generation (HHG) with stable and tunable carrier-envelope phase (CEP), and with full control of their polarizations. Unlike HHG, X-ray attosecond pulses from FEL have sufficient intensities that permit the realization of the holy grail (atto-pump/atto-probe experiments) of attosecond physics. Use of circularly or elliptically polarized attosecond light opens the possibility of presently investigating and manipulating linear and nonlinear effects that are not accessible with linearly-polarized pulses. In this talk, after briefly introducing the physical mechanisms at the basis of attosecond pulse generation, I will focus on our numerical and analytical methods for the investigation of ultrafast ionization processes in atoms and molecules of astrophysical interest, with emphasis on two-electron processes in which electron correlations play a key role. Enabled by the broad bandwidth of attosecond pulses, the first unusual effect we predicted in double photoionization of H2 by an intense few-cycle elliptically polarized attosecond pulse is the molecular symmetry-mixed dichroism (MSMD. The other effect is the novel electron phenomenon of electron vortices in attosecond photoionization of atoms and molecules, which provides a dramatic example of wave-particle duality. Our predictions of electron matter-wave vortices, which have now been observed experimentally, have already opened a new interdisciplinary area in physics.


Prof. G. Gibson

Physics Department (primary), College of Liberal Arts and Sciences, UConn Master Calendar

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