Robert Hofstadter; Physics Nobelist : Science: The retired Stanford professor won the prize in 1961 for his work on atomic nuclei.

Robert Hofstadter, who won the Nobel Prize in physics in 1961 for his research into the nuclear particles that are the building blocks of the universe, has died at his home on the Stanford University campus, it was learned Monday.

Hofstadter, who said his most important discovery was made outside the public spotlight, was 75 when he died Saturday of heart failure at the university where he had worked since 1950.

He was honored in 1961 by the Royal Swedish Academy of Science for determining the precise size and shape of the proton and neutron inside the nuclei of atoms.

But he felt his 1948 discovery and invention of sodium iodide--a crystal laced with the element thallium that is used in research to detect subatomic particles--was of more significance than the research that led to the Nobel.

“There is work I did for which I have never received any recognition and which I think is of comparable importance,” Hofstadter told the Associated Press several years ago.

“He made the discovery in 1948 and he’s very proud of it,” Douglas Hofstadter said from his father’s home. “Most people didn’t even know he was responsible for it.”

Sodium iodide, used in particle accelerators, gives off light sparks when hit by normally unseen particles. Still in use, it has led to discoveries of subatomic particles even smaller than protons and neutrons.

Using his lesser known discovery, Hofstadter and his colleagues worked for a decade to probe atomic nuclei by directing a beam of electrons from a 220-foot linear accelerator to get a clearer picture of their structure.

“He was somebody who was very much a believer in the beauty and simplicity of nature, which led him down certain pathways and made him want to understand the innermost part of the smallest particles,” Douglas Hofstadter said.

Born in New York, Hofstadter was a product of that city’s public colleges and he went on to receive a master’s degree and a doctorate from Princeton University before he moved to California to teach and do research at Stanford.

In World War II, Hofstadter was a physicist at the National Bureau of Standards, where he helped develop the proximity fuse, an antiaircraft weapon that detonated a shell when it detected approaching objects by radar.

Hofstadter retired in 1985 after 35 years at Stanford, but he continued research into coronary angiography, a technique for exploring heart functions with radioactive substances instead of catheters, which are painful and can be fatal.

The professor also had an athletic and musical side, enjoying skiing, Stanford sports events and jazz, particularly from the 1920s and 1930s. He also spent time on his 800-acre cattle ranch in the tiny Northern California town of Flournoy.

Hofstadter remained active until his death, according to his family. Asked once if his curiosity had been sated over the years, he replied, “I’d rather be spared such satisfaction because then I’d have nothing to do.”

Hofstadter also had theories outside the world of science, advocating that each American home be provided an electronic voting machine in order to establish the classical Greek form of democracy in this country.

Besides his son, he is survived by his wife, Nancy; two daughters, a brother, a sister and two grandsons.