Experimental evidence for a virtual state in a cold collision: Electrons and carbon dioxide - art. no. 022708

Experimental data are presented for the scattering of cold electrons by CO2 , for both integral and backward scattering, down to energies of a few meV with an energy resolution of 0.95-1.5 meV (full width at half maximum) in t he electron beam. The experimental data show evidence for the phenomenon of virtual-state scattering, a subject of extensive theoretical study. The me asured scattering cross sections rise rapidly at low energy, to a limiting value in integral scattering in excess of 120 Angstrom (2). In addition, an alysis shows that scattering is s-wave dominated and that the s-wave scatte ring length is negative. All features are characteristic of virtual state s cattering.