New Critical Compilations of Atomic Transition Probabilities for Neutral and 

                                  Singly Ionized Carbon, Nitrogen and Iron*

                                               W. L. Wiese and J. R. Fuhr

       National Institute of Standards and Technology, Gaithersburg, MD 20899

   
    Because of the strong astrophysical interest in the above cited spectra and 
because of new literature data of significantly improved quality, we have 
undertaken new critical assessments and tabulations of the transition 
probabilities of important lines of these spectra. For Fe I and Fe II, we have 
carried out a  complete re-assessment and update, and we have relied almost 
exclusively on the literature of the last 15 years, so that this new compilation 
supersedes our 1988 data volume. Our new tables are about 25% larger for 
Fe I and almost 50% larger for Fe II, and the estimated accuracies are now
for the majority of lines in the 3 - 10% range for Fe I and in the 10 - 25% band 
for Fe II.Our updates for C I, C II and N I, N II address primarily the persistent lower transitions involving principal quantum numbers 2 and 3, as well as a 
now greatly expanded number of forbidden lines (M1, M2, and E2). For these
transitions, sophisticated multiconfiguration Hartree-Fock (MCHF) calculations
have been recently carried out, which have yielded data considerably improved
from our 1996 NIST compilation and have also yielded many additional forbid-den transitions. We plan to enter all this new material into our comprehensive
NIST Atomic Spectra Database (ASD).

*Supported in part by the NASA Office of Space Science