SIMBAD references

Emission lines from ions in the Be-like isoelectronic sequence can be used for reliable diagnostics of temperature and density of astrophysical and fusion plasmas over a wide range of temperatures. Surprisingly, interpolated data is all that is available for a number of astrophysically important ions. We have carried out intermediate coupling frame transformation R-matrix calculations which include a total of 238 fine-structure levels in both the configuration interaction target and close-coupling collision expansions. These arise from the configurations 1s²2{s,p}nl with n=3-7, and l=0-4 for n ≤5 and l=0-2 for n=6,7. We obtain ordinary collision strengths and Maxwell-averaged effective collision strengths for the electron-impact excitation of all the ions of the Be-like sequence, from B⁺ to Zn²⁶⁺. We compare with previous R-matrix calculations and interpolated values for some benchmark ions. We find good agreement for transitions n=2-2 with previous R-matrix calculations but some disagreements with interpolated values. We also find good agreement for the most intense transitions n=2-3 which contribute via cascade to the (n=2) diagnostic radiating levels.