Abstract

It is nowadays possible to produce isolated attosecond pulses in the XUV photon energy range (~90 eV) [1]. These can be employed in combination with infrared (IR) pulses in IR field dressed photo-ionisation experiments to investigate attosecond dynamics in XUV pump IR probe schemes [2]. Specific chromophores in large biomolecules have a high photo excitation cross-section in the VUV range (10-20eV) [3]. Therefore attosecond VUV pulses will enhance the excitation fraction of a molecular sample and allow direct atto-pump atto-probe experiments. We discuss how we plan to produce efficient HHG radiation in this range. The target is optimised to achieve high photon flux and a sub-fs pulse. We discuss the set up for an absolute measurement of the photon flux in combination with spectral and temporal characterisation of the pulse [4] necessary for such an optimisation. We discuss the modelling of the optimisation process according to phase matching calculations [5] and 2D/3D time dependent Schrödinger equation (TDSE) numerical simulations [6]. Fig. 1: (left) simulation of the sub-fs VUV pulse, (centre) measured calibrated spectrum for low harmonics, (right) current setup schematics with monochromator for flux measurement

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