Issues

Belts of charged particles surrounding the earth were a surprising discovery of the early artificial satellites. In eight years much has been learned about their geometry and injection and loss mechanisms, but many questions remain.

Sir Mark continues his personal recollections of Ernest Rutherford and Ernest Lawrence. By 1935 precise mass determinations with nuclear reactions were being made at Cavendish. In the following years Rutherford was arranging for new facilities at the laboratory. Meanwhile Lawrence began to use the cyclotron for medical research, learned to extract a beam from the accelerator and found a lot of unexpected radiation. Two years after Rutherford's death, the discovery of fission opened a new era.

Controlled‐electron spectroscopy permits study of atomic levels not accessible with resonance radiation. With electron‐beam excitation, radiation selection rules no longer apply. Polarization data can reveal hyperfine structure, and when the technique is combined with paramagnetic resonance, lifetimes can be obtained from the resonance linewidths.

Among phenomena exhibited by nuclei whose masses range from 16 to 56 are pure single‐particle isobaric analog states and multipolarity mixings in radiative transitions between excited states.