Tombstones: The Stuff of Life

From the March 1973 Penn Stater: Legendary physicist Erwin Mueller shares stories of his scientific inventions, his introduction to Penn State, and how he used science to turn tombstones to bread in post–World War II Germany.

cover of March 1973 Penn Stater Magazine, a blue-tinted view through a microscope, from Penn Stater Archives

The ancient alchemists never could turn their lead into gold, but Penn State has a modern physicist who survived the ravages of World War II by turning tombstones into bread.

Dr. Erwin Mueller, known throughout the scientific world as the inventor of the field ion and atom probe microscopes and winner of a host of major prizes in his field, devised his life-saving tombstone-to-bread formula in East Germany in 1945.

The end of World War II had left him stranded in the Russian sector of East Germany with a wife and young daughter to feed, and “Russian recruiters” to escape.

“We had almost nothing to eat,” the Evan Pugh Professor of Physics recalls. “The Americans brought food into their zone, but the Russians took out everything and everyone they could find to repair the damages wrought by Hitler’s scorched earth policy in their country.

“How do we live? Well, I would go out and collect a few broken marble gravestones, buy hydrochloric acid at the drugstore—you could get that because it wasn’t edible—and pick up a bucket of ammonia water at the city gas plant. Then I dissolved the marble in the acid to make carbon dioxide, piped it into the ammonia, and let it run a couple of hours. The result was an ammonium bicarbonate precipitate.

“After it dried out, I would pack the powder in little bags, which I trademarked artistically as ‘Dr. Mueller’s Finest Baking Powder,’ because that’s what I’d made, and the Germans hold the title ‘doctor’ in great respect. I’d bicycle around the countryside visiting farmers who had flour but no baking powder and trade my product for theirs. So that’s how I made bread from gravestones.”

And he adds with a smile: “It shows that it’s good to know a little chemistry, even if you are a physicist.”

By now, Dr. Mueller’s contributions to physics are well recognized. He began a whole new field of research—field emission and field ion microscopy. His microscope was a major scientific breakthrough, allowing man for the first time to see the atoms and to examine the surface structure of metals at the atomic level. Because of his work, more than 60 laboratories today are engaged in field ion microscopy, and an annual international conference in field emission is further evidence of his impact.

The August 1972 issue of Physics Today says: “The ultimate sensitivity in the study of surface geometry is the imaging of individual atoms. That such imaging should first be achieved not with computer-designed electron lenses, presided over by teams of skilled technicians, but rather with an instrument of unparalleled simplicity conceived and built by a single individual (Dr. Mueller) in a modest university laboratory, stands as a classic example of intellect triumphing over the bureaucratic system of financial support … the atom-probe field ion microscope … achieves the ultimate in sensitivity for both surface geometry and composition.”

Erwin Mueller grew up in Germany in the turbulent days following World War I. As a boy, his interest was engaged by both physics and astronomy, but after the 1929 Crash and the ensuing worldwide depression, he decided to concentrate on the former because, in those years before the space era, there were very few job opportunities in astronomy.

“Scientifically, it was a highly exciting time,” Dr. Mueller remembers. “There were seven Nobel laureates in the Physics Colloquium at Berlin University—geniuses like Max Planck, Erwin Schrodinger, Max von Laue, Peter Debye, Walther Nernst, Albert Einstein, and Gustav Hertz. Naturally, no student ever dared open his mouth at the Colloquium!”

Although Dr. Mueller was inclined toward an academic career, his path was blocked with the advent of the Nazis to power. Hitler demanded that all new professors be party members. Rather than submit, Dr. Mueller followed his research director, Professor Hertz, into industry to work on his doctoral thesis there.

“Hertz asked me what I wanted to do,” Dr. Mueller continues, “but beyond a feeling that it should be in electron physics, I really wasn’t certain. Because he was such a great scientist, he had an overview of the subject and could point to an area of investigation that was unknown but promising.”

The area was field emission and, as Dr. Mueller puts it, “From then on, I never let go.”

In 1936, Dr. Mueller invented the field emission microscope and asked his employer, Siemens, the largest electric concern in Germany, to add $50 to his $75 monthly salary. Siemens offered $25, so Dr. Mueller quit and went to work for a smaller firm which was developing electronic devices for voltage stabilizers.

“The vacuum tubes which I developed there were used in both German and British airplanes,” Dr. Mueller says, “since the company sold their patents to an English firm just a year before the war broke out. As a matter of fact, the British tubes, which I got from one of their planes shot down over Germany, were better than ours. They had purer raw materials from which to make them.

“The president of the company was a physicist as well as a businessman, and he permitted me to continue doing some basic research. In 1941, I discovered field desorption, a new physical effect which allowed me to evaporate metals at very low temperatures with the help of an electric field rather than by the use of high temperatures. I also started thinking of making a microscope that would show surface atoms with the help of this effect, but I really didn’t have any idea then of how to do it.”

Any attempts to continue his work, however, came to an abrupt end in 1944 when the company was destroyed in a nighttime bombing raid in which 48 of Dr. Mueller’s co-workers died. He survived only because the plant operated alternate night shifts, and his was off duty that evening.

“Our laboratory was transferred from Berlin and rebuilt,” he notes, “but by that time the war in Europe had ended. The little town of Altenburg where we were to work was conquered by Americans, but two months later they withdrew and left us to the Russians, so I found myself living in East Germany.

“But if I had still been in Berlin, I would have wound up in the Soviet Union. The Russians rounded up all the German scientists they could find and shipped them off. My research director, Professor Hertz, went to Russia along with several of his assistants. Twice, the Russians came to look for me, but I was warned and managed to hide.”

Dr. Mueller survived the years between 1945 and 1947 as a high school and chemical engineering school teacher. Most of the regular teachers had been fired because they were Nazis, but since he had never joined the party, he was able to find work. Finally, in 1947, he decided to go to West Berlin.

There, he was welcomed at the Kaiser-Wilhelm Institute (Now one of West Germany’s Max-Planck Institutes). Resuming his basic research in field emission microscopy, he obtained his doctor-habilitation degree, a prerogative for an academic career in Germany. At the institute, he formed and headed a department of field emission research, and in 1951 invented the field ion microscope. He also had a joint appointment as an “extraordinary” professor of physics at the Free University of West Berlin.

Dr. Mueller wound up at Penn State partly by chance. Before coming to America, he had been asked to visit the physics department here. Having never heard of Penn State before, he had almost forgotten the invitation when he embarked on a tour of the U.S. early in 1952. Planning a trip from New York to Pittsburgh, he happened to see the name “State College” on the map and decided to make a short stop.

“I gave a colloquium,” he remembers, “and afterwards they offered me a job. It was a warm spring night and my family and I were staying at the Nittany Lion Inn. It had a garden like our cottage on the grounds of the Institute in Berlin, and there was a light, soothing rain which I could hear falling on the roof. After all that noise and dirt of New York City, it was quiet and beautiful, and it seemed like this would be a nice place to raise our daughter.

“I guess you could say I just got stuck on the way to Pittsburgh, and I have never regretted it.”