ABSOLUTE MEASUREMENTS OF OPTICAL OSCILLATOR-STRENGTHS OF NOBLE-GAS RESONANCE LINES

We have remeasured the optical oscillator strengths of eight noble-gas resonance lines in the vacuum-ultraviolet region. The measurements us e a 900-eV collimated electron beam to excite the atoms, and the trans mission of the emitted radiation is measured as a function of the gas density. In the method of self-absorption used here, the measured osci llator strengths are proportional to the distance between the electron beam and the fixed aperture of the spectrometer-detector system. We i nvestigated and eliminated a possible systematic effect in the determi nation of the absorption length due to deflections of the electron bea m. These measurements are performed at higher energies than our previo us experiments at 100 eV in order to keep the electron-beam path bette r defined and aligned with the electron-gun apertures. The measured ab solute oscillator strengths are He I (58.4 nm), 0.2700+/-0.0076 (2.8%) ; He I (53.7 nm), 0.0737+/-0.0023 (3.1%); Ne I (74.4 nm), 0.010 95+/-0 .000 32 (2.9%); Ne I (73.6 nm), 0.1432+/-0.0038 (2.6%); Ar I (106.7 nm ), 0.0580+/-0.0017 (2.9%); Ar I (104.8 nm), 0.2214+/-0.0068 (3.1%); Kr I (123.6 nm), 0.1775+/-0.0050 (2.8%); and Kr I (116.5 nm), 0.1416+/-0 .0041 (2.9%).