Hydrogen Stark Broadening by Different Kinds of Model Microfields

The “method of model microfields (MMM)”, which has been employed successfully especially for the calculation of hydrogen Stark profiles, is based on the assumption that reliable line shapes may be obtained from just the probability density of the plasma microfield and its autocorrelation function. To test the influence of higher order statistical features two different model microfields have been used to investigate Stark broadening of hydrogen Lyman lines by either electrons or ions. Corresponding profiles computed in this way lie close together over the full intensity range, but systematic relative deviations of about 20% show up at frequency separations from the unperturbed line of approximately three times the plasma frequency (for electrons or ions, respectively), i.e., in the “transition region” where neither the impact nor the static approximation holds. Though the joint action of electrons and ions as well as Doppler broadening will tend to diminish these deviations, the present form of the MMM cannot be expected to yield an accuracy better than some 10% throughout the line profile.