Wavelength measurements of heliumlike 1s2s S-3(1)-1s2p P-3(0,2) transitions in Ne8+, Na9+, Mg10+, and Si12+ emitted by solar flare plasmas - art. no.022502

With the Solar Ultraviolet Measurements of Emitted Radiation instrument-a h igh-resolution normal-incidence telescope and spectrometer on beard the Sol ar and Heliospheric Observatory-heliumlike 1s2s S-3(1) -1s2p P-3(0,2) trans itions in the highly ionized species Ne8+, Na9+, Mg10+, and Si12+ were obse rved. The spectral lines were emitted by high-temperature solar hare plasma s. In this paper, we report on wavelength measurements of the He-like lines identified in the recorded spectra. The wavelength uncertainties we obtain ed from the solar measurements are less than or equal to 20 m Angstrom(1 si gma), and in one case less than or equal to 30 m Angstrom. This is comparab le to or better than the best determinations so far achieved for these heli umlike 1s2s S-3(1) -1s2p P-3(0,2) transitions with instrumentation in the l aboratory. For the Na9+ S-3(1)-P-3(2) transition we report what is to our k nowledge the first wavelength measurement. The knowledge of the accurate wa velengths can provide important checks on atomic structure calculations.