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
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.
Rescattering explained…..[2]
..…for a circularly polarized field, the probability of the ejected electron returning to the core electrons is much smaller
Xe ion beam targets…..
Saturated Volume fits for production of Xe2+ from Xe+ ion beam
Circular vs. Linear rate…
g = 0.5
Xe+
Xe2+
Unshifted
ADK tunnelling theory [1]
Same peak intensity I,
This is highlighted by shifting the circular ADK curves for Xenon;
Predicts the ionization rate as a function of intensity
Circular Rate > Linear Rate
Circular Constant field
Linear Oscillating field
Linear 1.3I
Circular I
matches
To experimentally compare linear and circular,
E0 / 2
1.3 * (E0 / 2)
Circular
Peak E-field
Linear
i.e. 0.81E0
Intensity I
0.65I
i.e. (0.81E0)2
Nonsequential Ionization of Xe and Xe+
Using the ISS technique [3], we have studied the single, double and triple ionization of Xe and the double ionization of Xe+
Loss of linear flux in Xe+ appears as an enhanced linear signal in higher charge states
Large enhancement of linear signal in the low intensity regions is due to the Nonsequential ionization!
Suppressed Nonsequential component from the ionic target!
Integrated Ion Yield (arb.)
Z Position (mm)
Xe3+ Xe
Xe+
Circular
Linear
Xe2+
Groundstate: Is= 1.6 x 1014 Wcm eV (IP= 21.2eV)
Metastable: Is= 3.8 x 1013 Wcm eV
Xe3+ from Xe2+ ion beam
Metastable population….
Xe %
Xe %
Metastable pop.
Good agreement with previous values [4]
Experimentally determined:
Experimental Verification of 0.65…
First determination of a precise value for the linear-circular intensity ratio needed for a direct comparison
New method for the precise determination of the metastable population of ion beams
Conclusion
Observed Nonsequential ionization in the double and triple ionization of Xenon
Results showed a suppression of the NS component for an ionic target as we previously observed for Ar+ [5] •
ISS of Ne target with Circular I and Linear 0.65I
Ne+ Ne
Circular
Linear
Z-scan results from Xe neutral target…
Z Position (arb.)
Time of Flight (sec)
Signal (arb.)
132Xe2+
131Xe2+
129Xe2+
Ne2+ Ne
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, (2002)
Results show excellent match of yields for this intensity ratio