Rescattering explained….. [2]

1. Interaction of Intense Ultrashort Laser Fields with Xe, Xe+ and Xe++ E M L English2, S L Watson2, W A Bryan2, W R Newell2 M Suresh1,4, J McKenna1, B Srigengan1, I D Williams1 C J Hooker3, E J Divall3, A J Langley3 1Dept. of Physics, Queen’s University Belfast, Belfast, BT7 1NN, UK 2Dept. of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK 3Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK 4International Research Centre for Experimental Physics, Queen’s University Belfast, Belfast, BT7 1NN, UK Rescattering explained…..[2] ..…for a circularly polarized field, the probability of the ejected electron returning to the core electrons is much smaller Circular vs. Linear rate… ADK tunnelling theory [1] Predicts the ionization rate as a function of intensity Same peak intensity I, Nonsequential Ionization of Xe and Xe+ Groundstate: Is= 1.6 x 1014 Wcm-2 19.9 eV (IP= 21.2eV) Metastable: Is= 3.8 x 1013 Wcm-2 7.8 eV Circular Rate > Linear Rate Circular Constant field Linear Oscillating field Using the ISS technique [3], we have studied the single, double and triple ionization of Xe and the double ionization of Xe+ matches Linear yield @ 1.3I Circular yield @ I Circular Linear This is highlighted by shifting the circular ADK curves for Xenon; Loss of linear flux in Xe+ appears as an enhanced linear signal in higher charge states Xe+ Xe2+ g= 0.5 Metastable population…. Integrated Ion Yield (arb.) Large enhancement of linear signal in the low intensity regions is due to the Nonsequential ionization! Unshifted Metastable pop. Xe+ 1.2% To experimentally compare linear and circular, Xe2+ 3.7% Linear Circular Peak E-field E0 / 2 1.3 * (E0 / 2) Xe Xe3+ Good agreement with previous values [4] i.e. 0.81E0 Xe+ Xe3+ Intensity I 0.65I Suppressed Nonsequential component from the ionic target! i.e. (0.81E0)2 Conclusion Z Position (mm) First determination of a precise value for the linear-circular intensity ratio needed for a direct comparison • Xe Ne Xe Xe+ Ne+ Xe2+ Circular Linear Z-scan results from Xe neutral target… Observed Nonsequential ionization in the double and triple ionization of Xenon • Signal (arb.) Results showed a suppression of the NS component for an ionic target as we previously observed for Ar+ [5] • New method for the precise determination of the metastable population of ion beams • Time of Flight (sec) Ne Ne2+ 132Xe2+ 131Xe2+ 129Xe2+ Z Position (arb.) A detailed experimental study of the interaction of atomic and ionic Xenon targets with intense short (50fs) laser pulses has been performed. Employing the intensity selective scanning (ISS) technique, a comparison is made between ionization via linearly and circularly polarized fields. Xe ion beam targets….. Saturated Volume fits for production of Xe2+ from Xe+ ion beam Xe3+ from Xe2+ ion beam Experimentally determined: Experimental Verification of 0.65… ISS of Ne target with Circular I and Linear 0.65I References (1) M.V. Ammosov et al, Zh. Eksp. Teor. Fiz. 91, 2008 (1986) (2) P. B. Corkum, Phys. Rev. Lett. 71, 1994 (1993) (3) A. A. A. El-Zein et al, Phys Scripta, T92, 119 (2001) (4) P. Varga & H. Winter, Phys. Rev. A, 18, 2453 (1978) (5) J.B. Greenwood et al, Phys. Rev. Lett. 88, 233001 (2002) Results show excellent match of yields for this intensity ratio