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

Theoretical O iv electron density sensitive emission-line ratios, determined using electron impact excitation rates calculated with the R-matrix 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). The observed values of R1-R4, measured from high-resolution spectra obtained with the International Ultraviolet Explorer (IUE) satellite, lead to electron densities that are compatible, and which are also in good agreement with those deduced from line ratios in other species. This provides observational support for the accuracy of the atomic data adopted in the present calculations.