Hans Bömmel, who broke new ground in the field of high-frequency ultrasound, died from a lung infection on 19 March 2004 after a brief illness. Although he had gradually lost his vision and hearing a few years before his death, he had remained mentally alert.
Bömmel was born on 15 October 1912 in Munich to a German father and Russian mother. When he was barely three years old, his father died. Later, because of Bömmel’s ill health—presumably asthma—his mother moved the pair to Davos, Switzerland. There, he attended school and acquired his bachelor’s degree in sciences in 1932 at the German Alpine College called Fredericianum. His intelligence drew the attention of his teachers, and he began science studies the following year at the University of Zürich.
That same year, his mother became seriously ill, so Bömmel interrupted his studies to care for her until her death in 1935. His financial resources had dried up and, because it was a period of extreme hardship due to the worldwide depression, he accepted any work to be able to pay his bills. In 1939, he was drafted into the German army, the Wehrmacht. Fortunately, Zürich granted him Swiss citizenship that year, but as a consequence, he was drafted into the Swiss army.
Having completed his tour of duty during World War II, he returned to the University of Zürich, where he defended his doctoral thesis in 1943. His thesis, entitled “Measurement of Velocity and Absorption of Ultrasonic Waves in Gases by Means of Optical Methods,” was prepared under the guidance of his adviser, Richard Bär. Bömmel accepted an offer in early 1944 from EMPA, the Swiss Federal Material Testing Institute in Zürich, but stayed for only a few months before returning to the University of Zürich later that year as a postdoc of Edgar Meier. Meier was subsequently replaced by Hans Staub, who had previously been involved in the Manhattan Project.
Staub, an impulsive person, was a serious mismatch for the gentle and creative Bömmel. Gregor Wentzel recommended Bömmel for a postdoctoral position at Bell Labs in Murray Hill, New Jersey, and Bömmel joined the ultrasonics group of W. P. Mason there in 1953. During his first year at Bell Labs, he published spectacular results about the ultrasonic attenuation in normal and superconducting lead, four years before the Bardeen-Cooper-Schrieffer theory was published. His results became a cornerstone for a test of that theory. Barely two years later, he published his results on the magnetoaccoustic absorption in normal metals; those findings led to measurements of the Fermi surface’s diameter. At that time, theoretical methods of band structure calculations were developed intensively, and Bömmel’s method—besides others, such as measurements of the de Haas-van Alphen effect—was a welcome way of testing theoretical calculations.
In the late 1950s, Bömmel published a series of groundbreaking papers, with Klaus Dransfeld, on microwave acoustics. Those works inspired a number of developments, such as the acousto-optic modulator by Gary Starkweather at the Xerox Corp and the scanning acoustic microscope by Charles Quate of Stanford University. Bömmel’s collaboration with Dransfeld also led to an interesting application of microwave acoustics to the Mössbauer effect: testing the equivalence of gravitational and inertial mass by accelerating steel spheres in a vacuum in an inhomogeneous field up to the limit of mechanical strength of the spheres.
Bömmel left Bell Labs for UCLA in 1961 to establish a solid-state research group. While there, he extended his expertise to high-pressure physics and nuclear acoustic resonance. In 1968, he was offered a key position—for which he had been recommended by Nobel laureate Max Delbrück—involving setting up the physics faculty at the new University of Konstanz in Germany. Bömmel found the job offer attractive because he would be able to develop both new ideas for research and new teaching methods, plus interact with members of the various faculties, and he accepted it.
His early years at Konstanz coincided with the period of student rebellion known as the ‘68 movement, in which leftist radicals questioned the authority of more experienced scientists and split various academic groups. Bömmel helped end the chaotic situation and restore the decision-making hierarchy among scientists at the university.
Having clear, rational concepts, Bömmel fought for his ideas. He was a conservative in the very positive sense who was open to new ideas and developments. For example, he established solid-state physics as the ideal subject of research in the physics department at Konstanz to offer the best possibility of interdepartmental collaboration.
Bömmel was an outstanding scientist with a wide spectrum of interests in and knowledge of history, cosmology, political science, and other topics, and a highly respected person because of his intelligence, foresight, integrity, and exemplary behavior as a boss and colleague. He was outspoken and often disarmingly quick witted, and could lash out against stubborn bureaucrats, dishonest people, or obsessed ideologists—whether they were colleagues, high-ranking politicians, superiors, or employees who reported to him. To those whom he opened his heart, he was a most enriching, stimulating, and caring friend.
His colleagues at the University of Konstanz feel privileged to have known Bömmel and are most grateful for his kind and exemplary leadership and keep fond memories of this great man.
