Absolute cross section for electron-impact ionization of He(1s2sS3)
AbstractWe present an experimental determination of the electron-impact ionization cross section of the 1s2sS3 state of helium, for which there is a serious long-lasting discrepancy between theory and experiment. A technique for the production of a fast, intense beam of helium in the 1s2sS3 state only has been developed for this purpose, based on photodetachment of the He− anion. The cross section is measured using the animated crossed beam technique. The present results are much lower than the experimental data of Dixon et al. [J. Phys. B 9, 2617 (1976)JPAMA40022-370010.1088/0022-3700/9/15/013] and are in excellent agreement with the calculation of Fursa and Bray [J. Phys. B 36, 1663 (2003)JPAPEH0953-407510.1088/0953-4075/36/8/317].