Systematics of M4 transitions

Reduced probabilities of known ?? transitions of M4 multipolarity are analyzed. Hindrance factors of 95 M4 transitions are calculated and presented. It is shown that the investigated M4 transitions are inhibited in regard to estimates using Moszkovsky formulas, and their mean hindrance factor is 5.5. The factors are close to unity in two cases only, but the intensity of a weak M4 transition could be overestimated in an experiment due to the summation effect. Dependences of the hindrance factors on the number of protons and neutrons are shown for M4 transitions between states with dominant single-particle components ??1g9/2 ?? ??2p1/2, ??1h11/2 ?? ??2d3/2, and ??1i13/2 ?? ??2f5/2.