Rate equations for collisional processes are formulated and used to obtain the minimum electron density necessary to ensure LTE of a particular atomic species, with particular attention to the existence of low-lying metastable levels The final expression is compared with an earlier criterion of Griem The results of various experiments on plasmas containing one or more ionization stages of helium, nitrogen, oxygen, and argon are discussed The importance of making reliable estimates of collision strengths, for excitation involving metastable levels, is emphasized

Criteria for local thermal equilibrium in non-hydrogenic plasmas

Shift measurements for the H/sub alpha/ (1640 A) and P/sub alpha/ (4686 A) hydrogenic ion lines of He II have been done over an electron density range 2 x 10/sup 22/ to 2 x 10/sup 23/ m/sup -3/ and for an electron temperature of 4 eV The plasma was produced in a linear Z discharge Systematic red shifts linear in density are observed The experimental data are compared with combined theoretical estimates for electron-impact and ion quadrupole effects The experimental results are in agreement with our earlier results for P/sub alpha/ AE

Plasma shifts of the He II H alpha and P alpha lines.

Improved Stark-profile calculations for the He II lines at 256, 304, 1085, 1216, 1640, 3203, and 4686 A.

Measurements of Stark profiles of the He II line at and of the He II line at from a well diagnosed plasma of a gas-liner pinch discharge are reported. The plasma parameters were determined independently by Thomson scattering, and we found - , - 7.5 eV when measurements of the He II line were carried out and - , - 5.4 eV for the He II measurements. We compare widths and shifts of the spectral lines with theoretical approximations and present new empirical scalings. While the width of the He II line shows significant discrepancies with lineshape theories, in the case of the He II line profile we find good agreement with some calculations. In particular, to investigate ion dynamic effects we present an accurate measurement of the dip in the centre of the spectral line.

Investigation of the He II and He II transitions at high densities

We present a detailed investigation of the transition properties for He-like Al embedded in hot and dense plasma environments. The correlation effect between the bound electrons is treated with the configuration interaction method. Plasma screening on the nucleus is described using the self-consistent-field ion sphere model. Transition energies, transition probabilities and weighted oscillator strengths decrease quickly with the increase of free electron densities, but increase slightly with the electron temperature, and approach those of the uniform electron density ion sphere model at a given average free electron density. The results reported in this work are useful for plasma diagnostics.

Transition energies, transition probabilities and weighted oscillator strengths of He-like Al in hot and dense plasmas

Plasma polarization shift for resonance line of ionized He in shock tube due to negative space charge

Observation of a plasma polarization shift for the resonance line of ionized helium

He II alpha lines scanned by electromagnetically driven T tube, comparing with Stark broadening theory

T. Oda

Papers

Observation of a plasma polarization shift for the resonance line of ionized helium

Stark-profile measurements for the first four n-alpha lines of ionized helium