Excitation-Dependent Characteristics of H and He11 Lines used in Determining the Rydberg Constant
Series (1) has given an excellent general review of the situation concerning the Rydberg constant, and there is no need to elaborate here. Basically the problem is that most of the data on which the presently recommended value of the Rydberg constant is based was obtained more than thirty years ago, and that as a result of more recent advances in instrumental technique and in the understanding of various complications arising from the methods used in exciting hydrogen-like spectral lines there is the risk of uncertain systematic errors in the old data and the possibility of improved precision of future measurements. It is satisfying that at this conference there are two papers (2,3) from different laboratories reporting progress on new evaluations of the Rydberg constant based on measurements of deuterium and ionized helium. Since many of the technical complications in measuring hydrogen-like lines will be discussed in those papers, this paper will concentrate on the effects different excitation techniques can have on the appearance of these lines. The effects are of concern in measuring the Rydberg constant because the complicated fine structures of hydrogen-like lines are never fully resolved, and knowledge of the relative intensities and widths of the components is necessary for most satisfactory correction for blending. Moreover, it would be obviously advantageous if a method for producing very narrow hydrogen-like lines could be discovered.
KeywordsAtomic Beam Hollow Cathode Excitation Technique Rydberg Constant Neutral Helium
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