Absolute measurements of optical oscillator strengths of noble-gas resonance lines.

Abstract

We have remeasured the optical oscillator strengths of eight noble-gas resonance lines in the vacuum-ultraviolet region. The measurements use a 900-eV collimated electron beam to excite the atoms, and the transmission of the emitted radiation is measured as a function of the gas density. In the method of self-absorption used here, the measured oscillator strengths are proportional to the distance between the electron beam and the fixed aperture of the spectrometer-detector system. We investigated and eliminated a possible systematic effect in the determination of the absorption length due to deflections of the electron beam. These measurements are performed at higher energies than our previous experiments at 100 eV in order to keep the electron-beam path better defined and aligned with the electron-gun apertures. The measured absolute oscillator strengths are He I (58.4 nm), 0.2700\ifmmode\pm\else\textpm\fi{}0.0076 (2.8%); He I (53.7 nm), 0.0737\ifmmode\pm\else\textpm\fi{}0.0023 (3.1%); Ne I (74.4 nm), 0.010 95\ifmmode\pm\else\textpm\fi{}0.000 32 (2.9%); Ne I (73.6 nm), 0.1432\ifmmode\pm\else\textpm\fi{}0.0038 (2.6%); Ar I (106.7 nm), 0.0580\ifmmode\pm\else\textpm\fi{}0.0017 (2.9%); Ar I (104.8 nm), 0.2214\ifmmode\pm\else\textpm\fi{}0.0068 (3.1%); Kr I (123.6 nm), 0.1775\ifmmode\pm\else\textpm\fi{}0.0050 (2.8%); and Kr I (116.5 nm), 0.1416\ifmmode\pm\else\textpm\fi{}0.0041 (2.9%).