Talk - Henri Bachau: Nondipole effects in atoms interacting with intense soft x-ray laser pulses

20.02.2019 | Grete Flarup

Dato tor 21 mar
Tid 14:15 15:00
Sted 1525-626

Speaker: Henri Bachau, Centre des Lasers Intenses et Applications, Université de Bordeaux-CEA-CNRS, 33405 Talence Cedex

Abstract: The advent of free electron lasers delivering x-rays at high intensity opens the way to the exploration of new regimes in physics, chemistry and biology. Free electron lasers deliver now intensities of the order of 1017-1018 W/cm2 [1,2,3] and even more in x-ray regime, opening the way to explore nonlinear effects at short wavelengths. The breakdown of the dipole approximation in x-ray regime has been reported in the late 1920s with its effects on photoelectron angular distributions (PADs). The nondipole (or retardation) effects arise from the terms A.P and A2 in the Hamiltonian (where A denotes the field vector potential and P the momentum operator). Generally the retardation correction associated with A.P dominates, it explains in first-order the deviation of the PADs from dipole approximation [4]. Nevertheless, at high intensity, nonlinear effects (involving the emission and absorption of photons) associated with the diamagnetic term A2 become important. For example, we have demonstrated that the contribution of A2 dominates in stimulated Compton [5] and Raman scattering [6] in the contexts of two-color fields or one-color ultra-short pulses. During the presentation I will review these processes as well as recent work on photoionization of helium at ultra-high intensity in soft xray regime.

References:

[1] L. Young et al, Nature (London) 466, 56 (2010)

[2] G. Doumy et al, Phys. Rev. Lett. 106, 083002 (2011)

[3] H. Fukuzawa et al, Phys. Rev. Lett. 110, 173005 (2013)

[4] J.W. Cooper, Phys. Rev. A 42, 6942 (1990) and errata in Phys. Rev. A 45, 3362 (1992)

[5] H. Bachau, M. Dondera, V. Florescu, Phys. Rev. Lett. 112, 073001 (2014)

[6] H. Bachau, M. Dondera, V. Florescu, T.A. Marian, J. Phys. B: At. Mol. Phys. 50, 174003 (2017)

Institut for Fysik og Astronomi, Medarbejdere, Offentligheden / Pressen
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