Photodesorption from ices has been suggested as a major desorption process explaining the observations of molecules in the cold interstellar medium. The determination of photodesorption yields from ice analogues has been the subject of many studies in the last decade, however, the mechanisms explaining the desorption are still poorly understood. In this collaborative project, the groups at Sorbonne and at Hannover combine and share their respective expertise to shed new insight onto the photodesorption dynamics of ices. We propose a truly novel experimental approach by using the 3D-velocity map imaging (VMI) method for the analysis of the photodesorption from ices (VMICES: velocity map imaging from ices). Irradiation of condensed CO, N2, NO and H2O ices with photons in the range between 7-14 eV (VUV-laser or synchrotron radiation) will lead to desorption of molecules or fragments for which the velocity and angular distributions will be measured for the first time.

It is precisely the capability of measuring angular distributions which allows one to make the otherwise challenging distinction between different photodesorption mechanisms from ices. Electrostatic repulsion, energetic photochemical channels or momentum transfer channels are all likely to have different angular signatures in their desorption channels, but would otherwise be difficult to disentangle based on the kinetic energy distribution alone.

The SPICES-VMI setup will be completed, tested, and employed for experiments ranging from photodesorption experiments on ices to desorption of small organic chiral molecules in space using circularly polarised light.