FORBIDDEN LINES OF [OI] IN THE HIGH-RESOLUTION OPTICAL-SPECTRA OF PLANETARY-NEBULAE

Electron impact excitation rates for transitions in OI, calculated wit h the R-matrix code, are used to derive the electron-temperature sensi tive emission-line ratio R=I(2s(2)2p(4 1) D-2s(2)2p(4 1) S)/I(2s(2)2p( 4 3) p(1,2)-2s(2)2p(4 1) D)=I(5577 Angstrom)/I(6300+6365 Angstrom), fo r a range of electron temperatures (T-e=5000-20 000 K) and densities ( n(e)=10(4)-10(6) cm(-3)) applicable to planetary nebulae. Experimental values of R for a number of planetaries have been measured from high- resolution (similar to 0.6 Angstrom,FWHM) spectra obtained with the Ha milton Echelle spectrograph on the 3-m telescope at the Lick Observato ry. These measurements should be particularly reliable, as the sample of planetaries was restricted to those with large enough radial veloci ties for the nebular [OI] 5577 Angstrom emission to be red- or blue-sh ifted from the atmospheric ah-glow feature by a sufficient amount for the former to be reliably determined. Electron temperatures deduced fr om the observed values of R are generally in good agreement with those derived from T-e-sensitive line ratios in other species, providing ob servational support for the accuracy of the atomic data adopted in the calculations.