Robert Hofstadter | Biography

Hofstadter was born in New York City on February 5, 1915. He attended elementary and high school in New York City and received his bachelor of science degree from the City College of New York (now the City University of New York). He went on to earn both master's and doctoral degrees in physics at Princeton University, the latter in 1938. During World War II, Hofstadter worked for the National Bureau of Standards. From 1946 to 1950, he was on the faculty at Princeton. Then, in 1950, he moved to Stanford University. He became full professor and head of the physics department at Stanford in 1954.

Hofstadter's major field of interest has been the structure of the atomic nucleus and of the particles that it contains. In the 1920s, G. P. Thomson had used x-ray s and low-energy electron beams to study the structure of atoms. He had been able to show the location of nuclei and electrons within an atom on the basis of diffraction patterns produced by the X-rays and electron beams.

It occurred to Hofstadter that he might use a similar method to investigate the structure of atomic nuclei. By using electron beams of considerably more energy than those employed by Thomson, Hofstadter hoped to obtain diffraction patterns from nuclei and, perhaps, from particles within nuclei.

Hofstadter was able to use the Stanford Linear Accelerator for this research. Electrons produced in this machine had an energy of 100-500 Mev (million electron volts), sufficient to allow them to pass very close to nuclei.

The first diffraction patterns obtained by Hofstadter provided good detail about nuclear structure. They allowed Hofstadter to determine the size and shape of simple nuclei such as those of hydrogen-2 and hydrogen-3, helium-3 and helium-4, carbon, oxygen, and calcium. He also found that nuclei are surrounded by a very thin "skin" no more than 2.4 x 10^-13 cm thick. Within this "skin," nuclei seem to have uniform density.

Using a similar technique, Hofstadter was next able to analyze the structure of protons and neutron s within the nucleus. He found that these particles are not simple points of matter but, instead, have complicated structures like that of the atom itself. He determined that protons and neutrons have similar structures and that both have diameters of about 10^-14 cm. His accounting of the details of atomic structure led to the discovery of new types of subatomic particles. For his studies on nuclear structure, Hofstadter was awarded a share of the 1961 Nobel Prize for physics.