Angular distribution of neutral hydrogen following collisional electron detachment from H- at 2, 4, and 6 MeV
The angular distribution of neutral hydrogen atoms following electron detachment from H- ion beams has been measured at 2, 4 and 6 MeV for targets of nitrogen and hydrogen gas. For this purpose, a vertically oriented, slit shaped H- beam was developed with lateral opening angle of about 3 μrad. When account is taken of the angular acceptance of the slit detector system, good agreement is found with existing Born approximation theory for the scattering process [Wright, Franz and Genoni, Phys. Rev. A 32, 1215 (1985)]. The angular distributions are very sharply forward peaked. At 4 MeV, on a hydrogen target, the measurements are compatible with a relative differential cross section, of which the width at half maximum is about 7 μRAD results were similar on nitrogen. Measurements were also made at the same energies on a nitrogen target for outgoing hydrogen atoms in the 2S first excited state. Coincidence with the induced decay of the Lyman-alpha photon defined the signal. For these cases the experimental width at half maximum was almost three times greater than that for the undifferentiated neutral state. An account will be given of the experiment, including mention of diagnostic charge fraction measurements on nitrogen, and the results will be compared with theory.