ELECTRON-DENSITY DIAGNOSTICS FOR GASEOUS NEBULAE INVOLVING THE O-IV INTERCOMBINATION LINES NEAR 1400-ANGSTROM

Theoretical O iv electron density sensitive emission-line ratios, dete rmined using electron impact excitation rates calculated with the R-ma trix code, are presented for R1 = I(1407.4 angstrom)/I(1401.2 angstrom ), R2 = I(1404.8 angstrom)/I(1401.2 angstrom), R3 = I(1399.8 angstrom) /I(1401.2 angstrom), and R4 = I(1397.2 angstrom)/I(1401.2 angstrom). T he observed values of R1-R4, measured from high-resolution spectra obt ained with the International Ultraviolet Explorer (IUE) satellite, lea d to electron densities that are compatible, and which are also in goo d agreement with those deduced from line ratios in other species. This provides observational support for the accuracy of the atomic data ad opted in the present calculations.