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Tuesday, 22 October 2013

Thoma: DM: The Water Project

I will present two new types of targets which could get implemented in the red dragon lab over the next few months. The novelty of these targets lie in the fact that they make the liquid phase of matter available in our lab.

The 1st project looks into using a thin liquid water sheet as the generation medium for high harmonics. Gravity driven aqueous thin film technology has been demonstrated at atmospheric pressure [1] but I believe that with adequate design considerations we should be able to move it inside the vacuum tin. "non perturbative" harmonic generation has been demonstrated converting a mid-IR laser to visible wavelengths [2].

The 2nd project will be looking at 100nm sized silicon nitride cells to hold water in the transient absorption beam-line. Once the targets exists, a range of experiments can be thought of: one of the 1st ones I would like to try would be the time resolved generation of H3O+ following the 2 to 4 photon ionisation of H2O by a 400nm field by looking at absorption by the 3rd IP of H3O+ around 32eV [3]. This has been theorised to happen in 10's of fs but to my knowledge has never been measured.

Our collaborators from epfl would be keen to look at some vibrational excitation induced changes [4] in the absorption spectrum to use alongside some photo-electron spectra data acquired at ral last year.

During this presentation I will discuss both the science behind these experiments and the mechanical designs we hope to use to surpass the technical difficulties associated with combining XUV radiation and liquid phase samples.

[1] Rev. Sci. Instrum. 74, 4958 (2003); doi: 10.1063/1.1614874

[2] Vol. 17, No. 23 / OPTICS EXPRESS 20959

[3] J. Am. Chem. Soc. 128, 3864 (2006)

[4] science 297, 587 (2002)