Example of a VMI image

<p><strong>Figure 3.</strong> Example of a VMI image. Photon energy 23.95 eV, circular polarization. Sample: He. (a) Raw data. The arrow indicates the direction of propagation of the light. (b) pBasex [<a href="http://iopscience.iop.org/0953-4075/46/16/164007/article#jpb466820bib20" target="_blank">20</a>] reconstructed image (central part of image set to zero). (c) Photoelectron spectrum generated by angular averaging. (d) A polar plot of the angular distribution of the electrons in the outermost ring of the image where the polar angle is the angle between the direction of propagation of the light and the direction of emission of the elections and the distance from the origin of the plot is proportional to the intensity of electron emission in that direction.</p> <p><strong>Abstract</strong></p> <p>The low density matter end-station at the new seeded free electron laser FERMI@Elettra is a versatile instrument for the study of atoms, molecules and clusters by means of electron and ion spectroscopies. Beams of atoms, molecules and helium droplets as well as clusters of atoms, molecules and metals can be produced by three different pulsed valves. The atomic and molecular beams may be seeded, and the clusters and droplets may be pure, or doped with other atoms and molecules. The electrons and ions produced by the ionization and fragmentation of the samples by the intense light of FERMI can be analysed by the available spectrometers, to give mass spectra and energy as well as angular distributions of charged particles. The design of the detector allows simultaneous detection of electrons and ions using velocity map imaging and time-of-flight techniques respectively. The instruments have a high energy/mass resolution and large solid-angle collection efficiency. We describe the current status of the apparatus and illustrate the potential for future experiments.</p>