Beam-Foil Measurements of Oscillator Strengths for EUV Emissions of Nitrogen, Oxygen, and Sulfur Ions.
Abstract
Measurements of oscillator strengths for selected extreme-ultraviolet (EUV) transitions in nitrogen, oxygen, and sulfur were obtained using a beam-foil light source. A 2 MV Van de Graaff was modified to allow the introduction of different gases into the positive ion accelerator. The energy of the accelerator was calibrated by means of the ^{19}F(p,alpha ^{gamma})^ {16}O and ^{27} Al(p,gamma)^ {28}Si nuclear resonance reactions. The mass-analyzed and energy-regulated ion beam passed through a thin self-supporting carbon foil which produced a distribution of ionization species in various states of excitation in a high vacuum environment. The spectra were measured with a scanning vacuum-ultraviolet monochromator and an electron multiplier. For measurement of the time-dependent emission of a specific spectral line, the spectrometer wavelength was set on a single line and the output intensity recorded as a function of the distance from the foil. Optical calibration over the EUV 300-1400 angstrom region was determined from the comparison of measured branching ratios with theoretically calculated branching ratios in NeIII, Ne IV, OIII, and OIV. Branching fraction and lifetime measurements were combined to obtain oscillator strengths for selected transitions in NII, NV, OII, OIII, OVI, SII, and SIII, which have astrophysical interest.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1988
- Bibcode:
- 1988PhDT........34R
- Keywords:
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- Physics: Atomic