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VUV spectroscopy and photochemistry of ices relevant to outer solar system icy bodies


The optical properties of cryogenic water ices in the vacuum-ultraviolet spectral range are studied.


Vacuum ultraviolet (VUV) spectral region that includes far ultraviolet (FUV) from 200 nm - 120 nm and extreme ultraviolet (EUV) at shorter wavelengths below 120 nm has been used to determine gas-phase atomic and molecular composition. Many outer solar system ices also show characteristic absorption features in the FUV region, recently measured by the UVIS instrument on the Cassini spacecraft. However, optical constants of many of these ices in the VUV region are not available under these conditions (temperatures <120 K) and continuous spectral coverage has been difficult in laboratory conditions. We have used continuously tunable synchrotron radiation in the wavelength region between 250 nm and 120 nm and measured quantitatively transmission spectra of several pure and mixed ices containing H2O, NH3, CH4, CH3OH, O2, etc.

Experimental apparatus to determine optical properties of ices
Ice deposition chamber on beamline 4.

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