Survey of Some Systematic Properties of the Nuclear<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>E</mml:mi><mml:mn>1</mml:mn><mml:mn/></mml:math>Transition Probability

A survey of the experimental data for $E1$ transitions between levels below nucleon emission threshold in medium and heavy nuclei is presented. A general classification of these transitions is proposed and it is shown that, within most of the classes defined, the experimental "reduced" $E1$ transition probabilities differ by less than a factor ${10}^{4}$. The data are compared with specific nuclear model predictions. Precise theoretical descriptions of the anomalous parity states involved in $E1$ transitions exist in a few cases only. However it is often possible to link the observed behavior of $E1$ transition rates as a function of different parameters, with qualitative model predictions.The data available before 1 January 1965 are presented in tables including level lifetimes, quantum numbers, branching rati s, internal-conversion data, and deduced transition probabilities.