Electron Vortices Produced by Elliptically Polarized Attosecond Pulses
AMOP Physics Seminar
3:00 pm
Jorgensen Hall Room: 145
Speaker: Jean Marcel Ngoko Djiokap
Use of circularly or elliptically polarized light opens the possibility of investigating effects that are not accessible with linearly-polarized pulses. This talk presents new physical effects that are predicted for ionization of the helium atom by few-cycle, circularly or elliptically polarized attosecond pulses. For single ionization of He by two oppositely circularly polarized time-delayed attosecond pulses, we predict that the photoelectron momentum distributions in the polarization plane have helical vortex structures that are exquisitely sensitive to the time-delay between the pulses, their relative phase, their handedness, and the number of photons absorbed [1, 2]. The results manifest the ability to control the angular distributions of the ionized electrons by means of the attosecond pulse parameters [1,2]. Vortex patterns are also predicted in double ionization of He by circularly or elliptically polarized, time-delayed few-cycle attosecond pulses [3]. Our predictions are obtained numerically by solving the two-electron time-dependent Schrödinger equation for the case of elliptically polarized attosecond pulses. They are interpreted analytically using perturbation theory analyses of the various ionization processes [1-3]. Recently, our predicted spiral electron matter-wave vortices [1, 2] were experimentally observed in multiphoton single ionization of potassium atoms by a sequence of two counter-rotating circularly polarized femtosecond pulses [4].
[1] J.M. Ngoko Djiokap, S.X. Hu, L.B. Madsen, N.L. Manakov, A.V. Meremianin, and A.F. Starace, “Electron Vortices in Photoionization by Circularly Polarized Attosecond Pulses,” Phys. Rev. Lett. 115, 113004 (2015). This work was featured on the cover of the 11 September 2015 issue of Physical Review Letters. It is also a Research Highlight in Nature Physics 11, 800 (October 2015) and on the DOE BES web page: http://science.energy.gov/bes/highlights/2016/bes-2016-09-a/ .
[2] J.M. Ngoko Djiokap, A.V. Meremianin, N.L. Manakov, S.X. Hu, L.B. Madsen, and A.F. Starace, “Multistart Spiral Electron Vortices in Ionization by Circularly Polarized UV Pulses,” Phys. Rev. A 94, 013408 (2016). One of figures of this work has been selected by Physical Review A for Kaleidoscope, see the web page: http://journals.aps.org/pra/kaleidoscope/pra/94/1/013408 .
[3] J. M. Ngoko Djiokap et al., manuscript in preparation.
[4] D. Pengel, S. Kerbstadt, D. Johannmeyer, L. Englert, T. Bauer, and M. Wollenhaupt, “Electron Vortices in Femtosecond Multiphoton Ionization,” Phys. Rev. Lett. 118, 053003 (2017).
Use of circularly or elliptically polarized light opens the possibility of investigating effects that are not accessible with linearly-polarized pulses. This talk presents new physical effects that are predicted for ionization of the helium atom by few-cycle, circularly or elliptically polarized attosecond pulses. For single ionization of He by two oppositely circularly polarized time-delayed attosecond pulses, we predict that the photoelectron momentum distributions in the polarization plane have helical vortex structures that are exquisitely sensitive to the time-delay between the pulses, their relative phase, their handedness, and the number of photons absorbed [1, 2]. The results manifest the ability to control the angular distributions of the ionized electrons by means of the attosecond pulse parameters [1,2]. Vortex patterns are also predicted in double ionization of He by circularly or elliptically polarized, time-delayed few-cycle attosecond pulses [3]. Our predictions are obtained numerically by solving the two-electron time-dependent Schrödinger equation for the case of elliptically polarized attosecond pulses. They are interpreted analytically using perturbation theory analyses of the various ionization processes [1-3]. Recently, our predicted spiral electron matter-wave vortices [1, 2] were experimentally observed in multiphoton single ionization of potassium atoms by a sequence of two counter-rotating circularly polarized femtosecond pulses [4].
[1] J.M. Ngoko Djiokap, S.X. Hu, L.B. Madsen, N.L. Manakov, A.V. Meremianin, and A.F. Starace, “Electron Vortices in Photoionization by Circularly Polarized Attosecond Pulses,” Phys. Rev. Lett. 115, 113004 (2015). This work was featured on the cover of the 11 September 2015 issue of Physical Review Letters. It is also a Research Highlight in Nature Physics 11, 800 (October 2015) and on the DOE BES web page: http://science.energy.gov/bes/highlights/2016/bes-2016-09-a/ .
[2] J.M. Ngoko Djiokap, A.V. Meremianin, N.L. Manakov, S.X. Hu, L.B. Madsen, and A.F. Starace, “Multistart Spiral Electron Vortices in Ionization by Circularly Polarized UV Pulses,” Phys. Rev. A 94, 013408 (2016). One of figures of this work has been selected by Physical Review A for Kaleidoscope, see the web page: http://journals.aps.org/pra/kaleidoscope/pra/94/1/013408 .
[3] J. M. Ngoko Djiokap et al., manuscript in preparation.
[4] D. Pengel, S. Kerbstadt, D. Johannmeyer, L. Englert, T. Bauer, and M. Wollenhaupt, “Electron Vortices in Femtosecond Multiphoton Ionization,” Phys. Rev. Lett. 118, 053003 (2017).