Control and coherence of the few-particle continuum
Final Report Abstract
J. S. Briggs and co-workers: Ionisation is one of the most fundamental of atomic processes with great implications for plasma physics, atmospheric physics, radiation damage and many practical devices. This research program has been concerned with the understanding of ionization in terms of the structure of the many-particle correlated continuum and the ability through laser fields to control and manipulate the atomic and molecular continuum. Of the many results emerging during the course of this project I feel that the following might be termed highlights: a) The development of wavefunctions to descibe the correlated motion of several Coulomb-interacting unbound continuum particles. b) The demonstration that vortices in electron continua are responsible for exact zeros in ionization cross-sections. c) The consistent development and application of the Magnus expansion for the timedependent propagator for atomic and molecular systems subject to short, strong attosecond laser fields. This gives a simple explanation of the proposed manipulation of electronic wavepackets, either by periodic ionization and recombination or by controlling their motion in the continuum.. Above all the simplicity and accuracy of this approach which leads to analytic forms of the time-propagator, in a field where most theoretical methods are highly numerical, has been demonstrated. W. Strunz and co-workers: The loss of coherences in molecular (vibrational) dynamis was investigated under thermal and ultracold conditions. In the latter case, as we show convincingly, decoherence and damping is due to the (weak) interaction with a He droplet. The nanodroplet isolation technique allows to investigate the interaction of atoms or molecules with a unique, highly quantum environment. Our research highlights that a quantum dissipative description is capable of reproducing and explaining experimental results with K-2 and Rb-2 dimers on helium droplets. The good agreement between theoretical model and experiment suggests that the following mechanisms are active in dimers on helium droplets: a) Dissipation of vibrational wave packets. Moreover, associated vibrational decoherence explains the decay of the measured revival signal. b) Electronic decoherence and shift of electronic potential energy surfaces. c) In general, a desorption of dimers has to be taken into account, too: While (spin singlet) K-2 dimers quickly desorb off the droplet, the heavier Rb-2 (spin triplet) stay attached for a longer time. d) There is evidence that slowly moving vibrational wave packets move without friction on the surface of the superfluid host. This phenomenon should be studied in more detail in the future, for instance through using non-superfluid 3-He droplets as a host for attached molecules.
Publications
- (e,3e) on Helium at Low Impact Energy: the strongly correlated three-electron continuum, Phys.Rev.Lett. 98 193201 (2007)
M. Duerr, A. Dorn, J. Ullrich, S. P. Cao, A. Czasch, A. S. Kheifets, J. R. Goetz and J. S. Briggs
- Electron detachment from negative ions by few-cycle laser pulses: Dependence on pulse duration, Phys.Rev. A76 023423 (2007)
C. Arendt, D. Dimitrovski and J. S. Briggs
- Ionization and recombination of many-electron atoms and ions in strong, short laser pulses, J. Phys. 840 1 (2007)
D. Dimitrovski, J. R. Goetz and J. S. Briggs
- Decoherence of molecular vibrational wave packets: Oscillatory decay of purity, Phys. Rev. A77 AI2l11 (2008)
M. Schlesinger and W. T. Strunz
- Ionization in attosecond pulses: creating atoms without nuclei? New Jour. of Phys. 10 025013 (2008)
J. S. Briggs and D. Dimitrovski
- Magnus expansion for laser-matter interaction: application to generic few-cycle laser pulses, Phys. Rev. A79 043402 (2009)
M. Klaiber, D. Dimitrovski and J. S. Briggs
- Dissipative vibrational wave packet dynamics of alkali dimers attached to helium nanodroplets, Chem. Phys. Lett. 490,245-248 (2010)
M. Schlesinger, M. Mudrich, F. Stienkemeier and W. T. Strunz
- Theory of Deep Minima in (e,2e) Measurements of Triply Differential Cross Sections, Phys.Rev.Lett. 104, 03320r (2010)
J. H. Macek, J. B. Sternberg, S. Y. Ovchinnikov and J. S. Briggs
- Vibrational relaxation and dephasing of Rb-2 attached to helium nanodroplets, Phys. Chem. Chem. Phys. t3 681S (2011)
B. Grüner, M. Schlesinger, Ph. Heister, W. T. Strunz, F. Stienkemeier, and M. Mudrich
