Organisers

• Paul Durham (STFC Daresbury Laboratory, Great Britain)
• Carla Faria (Department of Physics and Astronomy, University College London, United Kingdom)
• Maciej Lewenstein (Institute for Photonic Sciences, Barcelona, Spain)
• Jens Biegert (Institute for Photonic Sciences, Barcelona, Spain)
• Wolfgang Sandner (Max Born Institut, Berlin, Germany)
• Misha Ivanov (Imperial College London, United Kingdom)

Supports

   CECAM

Description

In the past few years, considerable progress has been made in the attosecond imaging of matter and in the understanding of how complex systems interact with strong laser pulses. Concrete examples are the reconstruction of molecular orbitals [3], coherent control of molecular wavepackets [5], the probing of molecular vibration [6], or the investigation of high-order harmonic generation and ionization in clusters [7] and larger molecules [8].

There exists, however, a great deal of controversy, especially with respect to an accurate treatment of the targets in intense fields. This discussion goes beyond the current scope of strong-field laser physics and moves towards the fields of quantum chemistry and condensed-matter theory. 

Particular challenges in this context are:

An accurate treatment of the residual binding potentials and their influence on strong-field phenomena. For small systems, such as atoms or diatomic molecules, these potentials may be neglected to first approximation. Indeed, in this case one may still approximate the electron propagation in the continuum by a field-dressed plane wave. This underlying assumption has served as a backbone for most semi-analytical strong-field approaches [9]. For large molecules, clusters or solids, however, the  distinction between bound states and continuum states is less clear and it is a completely open question to which extent the residual potentials must be included in an adequate modelling of the electron propagation.  

An appropriate treatment of electron-electron correlation in complex systems.  It has been recently suggested that multielectron effects may be a major obstacle to attosecond molecular imaging using high-order harmonics, even for relatively simple molecules [10].  Such effects are also expected to play an important role for more complex targets. To the present date, already the interaction of a two-electron system with an intense field has posed a great challenge to theorists, and only recently has a completely ab initio computation been performed in the high-intensity, low-frequency regime [11]. For more complex systems, however, this approach seems a hopeless task. Relatively recent work using time-dependent density functional theory (TDDFT) looks very promising, if computationally non-trivial, for this problem [4].   Time-dependent R-Matrix theory has also successfully been applied to multielectron atoms in intense laser fields [12].

Scientific Objectives

This workshop would aim to bring the leaders of the above-mentioned fields together to assess where we are with the various theoretical and computational approaches to atomic problems and discuss the best ways to progress to the more complex systems mentioned above.   Apart from leading strong-field theorists, quantum chemists and condensed-matter theorists, in order to discuss whether the methods proposed are realistic, we are also inviting some of the key experimentalists worldwide. 

Computational Aspects

In a sense, this workshop covers one problem in quantum dynamics, one where perturbation theory of any sort is out of the question and accurate computations are essential but difficult.  There is a well-established set of codes to handle time-dependent density functional theory although many focus on linear response rather than strongly driven systems.  Other approaches may have difficulty in handling many-electron effects in realistic complex systems.  Thus there is a real computational issue facing the field.  The workshop should address the question of whether a collaborative effort to generate the required new codes would be useful and if so how should it be done.  

Training and Collaboration

We also intend that this workshop should provide training for young researchers.  Intense-field laser physics is very strong in some European countries, notably Germany, and is an emerging field in many others.  The workshop would provide young researchers from all over Europe with the unique opportunity of being immersed in the international strong-field community and interacting with leaders in the field.  The international community, on the other hand, would profit from the UK’s long-standing expertise in high-performance parallel computing, especially in the context of condensed-matter physics and quantum chemistry. 

References

[1] Y Mairesse, A. de Bohan, L.J. Frasinski, H. Merdji, L.C. Dinu, P.Monchicourt, P Breger, M. Kovacev, R. Taieb, B. Carré, H.G. Muller, P. Agostini and P. Salières, Science 302, 5650 (2003).

[2] M. Uiberacker, T. Uphues, M. Schultze, A.J. Verhoef, V. Yakovlev, M.F. Kling, J Rauschenberger, N.M . Kabachnik, H. Schroeder, M. Lezius, K.L. Kompa, H.G. Muller, M. J.J. Vrakking, S. Hendel, U. Kleinberg, U. Heinzmann, M. Drescher, F. Krausz, Nature 446, 7136 (2007).

[3] J. Itatani, J. Levesque, D. Zeidler, H. Niikura, H. Pepin, J. C. Kieffer, P. B. Corkum and D. M. Villeneuve, Nature 432, 867 (2004).

[4] See, e.g., F. Krausz, M. Ivanov, Rev. Mod. Phys. 81, 163 (2009) for a review on the subject.

[5] W. Boutu, S. Haessler, H. Merdji, P. Breger, G. Waters, M. Stankiewicz, L. J. Frasinski, R. Taieb, J. Caillat, A. Maquet, P. Monchicourt, B. Carré and P. Salières, Nature Physics 4, 545 (2008).

[6] S. Baker, J. S. Robinson, C. A. Haworth, H. Teng, R. A. Smith, C. C. Chirila, M.Lein, J. W. G. Tisch, J. P. Marangos, Science 312, 424 (2006).

[7] See, e.g., M. Ruggenthaler, S.V. Popruzhenko and D. Bauer, Phys Rev. A 78, 033201 (2008); A. Mikaberidze, U. Saalman and J. M. Rost, Phys. Rev. Lett. 102, 128102 (2009).

[8] R. Torres, N. Kajumba, J. G. Underwood, J.S. Robinson, S. Baker, J.W. Tisch, R. De Nalda, W. A Bryan, R. Velotta, C. Altucci, I.C. Turcu, and J. P. Marangos, Phys. Rev . Lett. 98, 203007 (2007); C.B. Madsen, L.B. Madsen, S.S. Viftrup, M. P.Johansson, T.B. Poulsen, L. Holmegaard, V. Kumarappan, K.A. Jorgensensen and H. Stapelfeldt, Phys Rev. Lett. 79, 043405 (2009).

[9] See, e.g., M. Lewenstein, Ph. Balcou, M. Yu. Ivanov, A. L'Huillier and P. B. Corkum, Phys. Rev. A 49, 2117 (1994).

[10] O. Smirnova, S. Patchkovskii, Y. Mairesse, N. Dudovich, D. Villeneuve, P. Corkum, and M. Yu. Ivanov, Phys. Rev. Lett. 102, 063601 (2009).

[11] J. S. Parker, B. J. S. Doherty, K. T. Taylor, K. D. Schultz, C. I. Blaga, and L. F. DiMauro, Phys. Rev. Lett. 96, 133001 (2006).

[12] See e.g., H.W. van der Hart, M.A. Lysaght, and P.G. Burke, Phys. Rev. A 76, 043405 (2007).