Statistical Fluctuations in Nuclear Evaporation

Previous treatments of nuclear evaporation have dealt with average values, neglecting fluctuations. In the present paper the fluctuations are considered in detail. The distributions of the number of neutrons and of the total energy associated with evaporation stars of a given size and the size distribution of stars of given total energy, are evaluated explicitly. Knowledge of the fluctuations is useful for interpretation of data concerning small stars, such as those produced by π-meson capture or by artificially accelerated particles. The fluctuations are not very important in the large stars and do not modify any of the results of the author's previous mean value calculations. The analysis of the mean evaporation process has also been put into a simplified form, from which numerical results can easily be obtained The method has been used to compare experimental data with various theoretical energy-temperature relationships; the Fermi gas law previously used by the author seems to be the most satisfactory connection between the high-energy star data and the observed level density at low energies.