A study of relative level populations in foil excited He and Li

Abstract

A set of relative level population measurements has been done for 40 keV beamfoil excited He and Li. The relative populations are discussed as functions of the principal quantum number, the azimuthal quantum number, the spin and the excitation energy.

A study of relative level populations in beam-foil excited Li, Be, and Mg

“…However, for estimating cascade contributions, relative level population data are needed, and only very few measurements have been done to obtain such quantities. Data have so far only been reported for H [2], He [3], Li [4], Be [5], C [6], Fe [7], and Zn [8]. Furthermore, in most of these works the data sets are very incomplete, so further experiments are clearly required to establish systematical trends as well as to guide a quantitative theory.…”

“…The level population is a quantity of basic interest, and we shall here give some examples of relative level populations as functions of the quantum numbers of the excited states at different projectile energies. The data reported previously for Li [4] and Be [5] were limited in the sense that only levels with low values of the principal quantum number were observed, and also that the observations were done only at one projectile energy. It is, of course, of basic interest to see whether the relative population of levels of the same charge state and with the same core configuration changes with the projectile energy, for a discussion of this see e.g.…”

“…The data given in this paper extend the old data for Li [4] and Be [5] to higher lying levels (generally up to levels with principal quantum number n~ 10) and to other pro- In the previous work on Be [5] attention was focussed on excitation functions for only a few low lying levels of Be I-Be III, the relative level population data given in [5] being sparse because of the lack of a quantum efficiency calibrated monochromator. This paper thus supplements [4,5].…”

“…Therefore only relative numbers are given. The relative line intensities, corrected for background, were converted into relative level populations by use of the relation [4,5] Here Nj is the relative population of level j, S(2jf) is the signal per monitor count of the optical transition of wavelength 2jr from level j to level f, K(2jf) is the monochromator quantum efficiency [11] at wavelength 2~f, and A~f is the transition probability for the transition from level j to level f. Repopulation through cascade processes were ignored, since the observation region was immediately behind the foil [4], and no attention was paid to polarization effects.…”

Relative and absolute level populations in beam-foil—excited neutral helium

“…As Andersen and co-workers have pointed out (52), the data may also be fit by an exponential equation of the form Cj e~^2 Tl . This is an unfortunate consequence of the fact that the easily observed spectral lines of helium I originate from the n = 3 to n = 6 levels.…”