Electron Impact Excitation of Xenon*

We have applied a novel experimental technique to measure cross sections for electron-impact excitation of the 5p$^5$6s and 5p$^5$6p states of xenon from its 5p$^6$ ground state. This is a complex collision system, for which benchmarking of theory against experiment is needed. The experiment is performed using ultrashort current pulses released from an electrode by femtosecond laser pulses with 80 MHz repetition rate. In order to minimize space charge effects, only about 10$^4$ electrons are generated in each pulse. Electrons are accelerated by a homogeneous electric field to energies of typically 250 eV. The fluorescence light generated in collisions with Xe atoms at low pressure (Pa range) is imaged perpendicularly and provides a direct image of the energy-dependent excitation cross section. The calculations were carried out with a fully relativistic and parallelized version of the B-spline R-matrix code [1], using a 75-state close-coupling model [2] with the target structure obtained earlier [3]. [1] O.~Zatsarinny, Comp.\ Phys.\ Commun.~{\bf 174} (2006) 273. [2] O.~Zatsarinny and K.~Bartschat, J.~Phys.~B: At.\ Mol.\ Opt. Phys.~{\bf 43} (2010) 074031. [3] O.~Zatsarinny and K.~Bartschat, Phys.\ Scr.\ T{\bf 134} (2009) 014020.