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The total cross sections of electron-impact single-K-shell ionization of 14 atomic targets ranging from H to U ͑1 ഛ Z ഛ 92͒ are calculated using a modified version of the BELI formula ͓Bell et al., J. Phys. Chem. Ref. Data 12, 891 ͑1983͔͒ by incorporating both ionic and relativistic corrections in it. The proposed modified Bell model with a single set of parameters is found to provide an excellent description of the experimental data in the reduced energy range 1 ഛ E / I K ഛ 10 6 ͑E and I K are, respectively, the incident energy and ionization poten-tial͒ with a performance level at least as good as any of the existing methods and models.

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The modified BELL (MBELL) formula (Haque et al 2006 Phys. Rev. A 73 012708) has been applied to the M-shell ionization of neutral and ionic atoms to deduce the `generalized' parameters of the 3s, 3p and 3d orbits. A single set of parameters for each of these orbits and that previously determined for each of 1s, 2s and 2p orbits can reproduce satisfactorily the features of the total electron impact ionization cross-sections (EIICS) of 21 M-shell targets in the Na, Mg, Al, Si, P, S, Cl, Ar and Ca isoelectronic sequences. The generalized parameters are also found to provide an excellent account of the M-shell EIICS data of Pb, Bi and U atoms at relativistic energies in the range from 20 to 250 MeV.

Spectra of heliumlike nickel, NiXXVII, have been observed from Tokamak Fusion Test Reactor (TFTR) plasmas with a high resolution crystal spectrometer. The experimental arrangement permits simultaneous observation of the heliumlike resonance line, the intercombination and forbidden lines, and all the associated satellites due to transitions ls 2 n£-is24'nA'' with n > 2. Relative wavelengths ami line intensities can thus be determined very accurately. The observed spectral data are in good agreement with results from the present Hartree-Fock-Slater atomic model calculations and predictions from the Z-expansion method. mm KSTBIBl'TION OF THIS DOCUMENT IS UNLIMITED