Special ''sum rules'' for the X-rays yield from protonium

This chapter derives a set of relations for the X-rays yield which are based on quite general properties of the cascade and result from balance equations for populations of atomic levels. Results of the theoretical calculations of cascade processes in protonium depend essentially on the -pp scattering lengths and involve some uncertainties due to model-dependent approximations in treating the Stark-mixing and de-excitation. Stark mixing, being effective for the states ngreater than or equal ton /SUB c/ , becomes unimportant at the low-lying levels n<n /SUB c/ , the critical value n /SUB c/ depending on the target density N. The applicability of the similar ''sum rules'' to other light exotic atoms is noted