Intermediate coupling branching fractions for UV transitions in ions of the Si and Ge sequences

The use of lifetime measurements for the specification of transition probabilities along isoelectronic sequences is hindered by the fact that virtually no branching fraction measurements exist for multiply charged ions. Part of the reason for this lies in the lack of calibration standards for intensity as a function of wavelength in the ultraviolet region. It has been shown that transitions of the form ns2np2 - ns2npn´s in Si I and Ge I are virtually free of configuration interaction, hence their branching fractions can be accurately predicted from intermediate coupling amplitudes deduced from measured spectroscopic energy level data. Reported here is the extension of these semiempirical methods to the ions P II, S III, Cl IV and Ar V in the Si sequence and As II, Se III and Br IV in the Ge sequence. This provides a set of branching fractions that can both specify transition probability rates from lifetime measurements for these ions, and serve as a set of lines of known relative intensities for use in the calibration of detection apparatus in the UV region.