Hans Dehmelt, who shared the 1989 Nobel Prize in Physics for developing methods to trap a single ion or electron, allowing for a more precise way to measure their properties, died March 7 in Seattle. He was 94. His wife, Diana Dundore, confirmed his death. Dr. Dehmelt devised a configuration of magnetic and electric fields known as an ion trap that serves as a cage for charged particles like ions and electrons. Once the particle was trapped, scientists could study it. In 1973, Dr. Dehmelt used the technique to observe a single isolated electron. He was later able to observe single ions in the trap. Dr. Dehmelt’s work “allowed us to measure the electron’s magnetism” — and that of its antiparticle, the positron — and to make “ultraprecise spectroscopic measurements of a single trapped ion,” Robert Van Dyck Jr., a physics professor emeritus at the University of Washington, where he worked with Dr. Dehmelt, wrote in an email. Dr. Van Dyck added that trapping a single charged particle “isolates the specimen from outside interactions” — like pressure and temperature — “that would affect the basic accuracy of the measurements.” Dr. Dehmelt (pronounced DAY-melt) shared half of the Nobel Prize with Wolfgang Paul, who did similar work at the University of Bonn in Germany. The other half went to Norman F. Ramsey, whose work on the structure of atoms and molecules led to the development of the atomic clock. When Dr. Dehmelt was informed that he had won a portion of the Nobel, he called Ms. Dundore at 2 a.m. “It was Hans asking me to marry him” after a nine-year courtship, she said in an interview on Friday. “I was excited and congratulated him and was very happy with his call,” she added, “but I thought the discussion of marriage should wait until daytime, when I was thinking clearly.” They were married about a month later, in time for them to travel to Stockholm, where he received his prize. Editors’ Picks Remember Snow Days?The Zen of Ice Climbing36 Hours in Mexico City Appropriately, his lecture began with a quotation from Albert Einstein. “You know,” Einstein had said, “it would be sufficient to really understand the electron.” Hans Georg Dehmelt was born on Sept. 9, 1922, in Gorlitz, Germany, to Georg and Asta Dehmelt, who ran an apartment house in Berlin. Mr. Dehmelt also had a law degree. An early interest in radios inspired young Hans’s interest in physics, and when he was 10, he entered the prestigious Evangelische Gymnasium zum Grauen Kloster in Berlin on a scholarship. “I supplemented the school curriculum with do-it-yourself radio projects until I had hardly any time left for my class work,” he wrote in his Nobel Prize autobiographical sketch. “Only tutoring from my father rescued me from disaster.” After graduation, he volunteered for the German Army, in which he served on a gun crew. He was captured during the Battle of the Bulge and spent a year as an American prisoner of war before his release in 1946. After the war, he earned master’s and doctoral degrees at the University of Göttingen, where his teachers included the physicists Robert Pohl and Werner Heisenberg. “When I was a graduate student,” he told The Seattle Times in 1989, “my teacher drew a dot on the blackboard and said, ‘Here’s an electron,’ but nobody had ever isolated one.” It became his ambition to do that. In 1952, Dr. Dehmelt immigrated to the United States. He was a postdoctoral researcher at Duke University before joining the University of Washington three years later as a visiting assistant professor. He stayed there until he retired in 2002. In addition to Ms. Dundore, he is survived by a grandson and a great-granddaughter. His son, Gerd, died in 2013. His first marriage ended in divorce. Blayne Heckel, the chairman of the physics department at the University of Washington, said Dr. Dehmelt’s work had not only provided insight into the laws of nature, but also resulted in advances in radio frequency techniques and “our system of weights and measures.”
