Marietta Blau

Austrian physicist

• Born: April 29, 1894; Vienna, Austria-Hungary
• Died: January 27, 1970; Vienna, Austria

Austrian physicist Marietta Blau advanced the field of particle physics by developing the photographic method of studying nuclear emulsions. Despite this breakthrough, she remains relatively unknown, although followers of her work have earned worldwide recognition.

Primary field: Physics

Specialty: Nuclear physics

Early Life

Marietta Blau (blow) was born in 1894 in Vienna, Austria-Hungary (now Austria), to prosperous upper-middle-class parents. Her father was a trial lawyer and successful sheet music publisher. Blau had three brothers, one of whom died in infancy. She was raised in the Jewish faith, which would ultimately shape much of her life and career.

Blau studied mathematics and physics at the University of Vienna, graduating in 1918. She earned her PhD in 1919. Her thesis on the absorption of gamma rays began her career in particle physics. In 1920, Blau moved to Berlin, Germany, and worked as an electrotechnical analyst for an X-ray tube manufacturer. The following year, she began her teaching career as an assistant at the University of Frankfurt’s Institute for Medical Physics. Her involvement in nuclear physics increased as she began instructing doctors in radiology. From 1923 to 1938, Blau worked with other scientists, many of whom were women, as an unpaid researcher at the prestigious Institute for Radium Research (Institut für Radiumforschung) in Vienna. Although Blau was never paid for any of her work at the Institute—she was told she had two strikes against her because she was both Jewish and a woman—it was here that she would do her most important work with emulsions.

Life’s Work

Emulsions are strips of film on which the tracks of alpha particles can be studied. When a charged energy ray is focused on an emulsion strip or plate, the paths of the nuclei, protons, electrons, and neutrons are ingrained. Typically, emulsions are plated with a silver salt composite such as bromide. Blau not only pioneered the development of emulsions, she also made several important discoveries using them.

In 1925, Blau collaborated with Swedish physicist Hans Pettersson and conducted her first experiments in tracking alpha particles by using photographic emulsions to find protons and other subatomic particles in the tracks made by charged rays. Over the next few years, Blau experimented with firing alpha particles at sheets of aluminum to observe the thin tracks the particles created. Among her published papers addressing the effects of the experiments are “The Photographic Effect of Natural H-rays” (1925) and “The Photographic Action of H-rays” (1928).

Blau’s collaborator and research assistant throughout much of the 1930s was her former student Hertha Wambacher. In 1932, Blau and Wambacher began experimenting with desensitizing processes intended to improve the visibility of emulsion tracks on various materials. They found that the tracks of the beta and gamma rays appeared clearly on the emulsions, while the grains of the particles often remained obscured. They then used photography chemicals to decrease the emulsion sensitivity and were successful in detecting both protons and neutrons in the alpha tracks and were able to show that proton tracks could be separated from other alpha particle tracks. In addition, Blau and Wambacher saw that the imprints of the beta and gamma rays were reduced while the presence of the alpha particles increased: The attempts to desensitize the photographic plates instead made them hypersensitive and showed the exact aspects Blau wished to observe.

Blau’s success was rewarded with a one-year grant from the Austrian Association of University Women. She used the funding to first work at Germany’s University of Göttingen with Professor Pohn on crystal physics and then went to Paris to work with Marie Curie at the Curie Institute to study the artificial disintegration of atoms using a photographic method. Blau then returned to Vienna to continue her study of neutrons with Wambacher, but the thickness of the film plates Blau and Wambacher were using soon became a major obstacle in their progress. Plates that were too thin resulted in poor tracking results. Thicker plates presented a series of other problems, such as decreased sensitivity and a loss of observable tracks when the plates became dry.

Renowned physicist Victor Hess offered to assist Blau and Wambacher in early 1937. They conducted a series of high-altitude experiments in an Austrian laboratory at Hafelekar Peak, near Innsbruck, and they found that when alpha particles were tracked at a high altitude, the results improved drastically and produced proton tracks at a length in excess of anything observed to date.

The photographic plates also showed star-like formations from which the paths of the alpha tracks expanded in several directions. These formations, which became known as Blau-Wambacher stars, were nuclear disintegrations caused by the cosmic rays.

Blau and Wambacher published a well-received paper in the journal Nature and expanded the high-altitude experiments by sending emulsion plates up in hot air balloons. Blau and Wambacher won the 1937 Ignaz L. Lieben Prize of the Viennese Academy of Science.

The improved sensitivity of the plates and the discovery of the star patterns had given Blau and Wambacher their first major breakthrough. The scientific community acknowledged their progress, and many physicists soon adopted the method.

Germany’s annexation of Austria in 1938 caused Blau to flee Vienna for Oslo, Norway, which halted her experiments with emulsion plates. She was stopped by Nazi officers who confiscated her scientific papers and notebooks. Without them, Blau never conducted follow-up experiments to her groundbreaking work.

On the recommendation of physicist Albert Einstein that same year, Blau left Europe entirely and moved to Mexico City. She found a job as a professor of physics at the Mexico City Polytechnic School, and while she continued to publish papers during this period, she had insufficient time and materials to conduct experiments. Blau moved to New York City in 1944 where she worked for several corporations before the end of World War II. She then took a position at Columbia University as a research physicist under the Atomic Energy Commission.

In 1950, Blau relocated to New York’s Brookhaven National Laboratory. However, she fell into contention with her colleagues and battled financial distress and health problems. In 1955 she became an associate professor at the University of Miami in Florida. In declining health, Blau moved back to Vienna in 1960, but her extended absence from her collaborators and materials contributed to her being largely unrecognized for her major advancements in particle physics.

Though most of her prewar colleagues were ousted from the Institute for Radium Research for their Nazi sympathies, several regained positions in physics and photographic analysis. Blau, however, remained without a career. She died of cancer in 1970 as a result of her exposure to radioactive substances over the years. Her obituary did not appear in any scientific publication.

Impact

Since her death, Blau’s work has gone virtually unrecognized, but her contributions to nuclear physics and nuclear fragmentation remain invaluable, particularly to those working in the subfields of particle physics, radiation, and photographic emulsion. Blau published sixty-five papers during her life and is credited as the first person to detect neutrons in a particle emulsion. Furthermore, it was her initiation of the photo-emulsion technique that led to the creation of particle and emulsion physics. Blau also conducted research in photography and precious metals, which were instrumental in her development of the photographic method of nuclear emulsions and her discovery that proton tracks and alpha particle tracks can be separated in an emulsion.

Her discoveries also led British physicist Cecil F. Powell to expand on the photographic emulsion method and develop it into an industry that by the 1950s replaced the bubble chambers previously used to study alpha particles. Powell received the Nobel Prize in Physics in 1950 “for his development of the photographic method of studying nuclear processes,” which surprised many because Blau’s pioneering work was never acknowledged.

Although never a recipient of the Nobel Prize, Blau was nominated several times by Austrian physicist Erwin Schrödinger. In 1962, she received the Schrödinger prize, a prestigious Austrian award. In 2009, the Vienna University of Technology developed the Marietta Blau TU Mobility Grant, which provides travel funds for young female scientists to present their findings at international scientific congresses. The Federal Ministry of Science and Research of Austria offers the Marietta Blau Grant for PhD students to study and conduct research abroad.

Bibliography

Byers, Nina, and Gary Williams. Out of the Shadows: Contributions of Twentieth-Century Women to Physics. Cambridge: Cambridge UP, 2006. Print. Provides biographies, accounts of discoveries, and discussion of important papers of forty women physicists from 1876 to 1976. Includes a chapter on Blau.

Rentetzi, Maria. Trafficking Materials and Gendered Experimental Practices. New York: Columbia UP, 2008. Print. Explores the experimental practices of radioactivity research in early twentieth-century Vienna and the differences in experimental cultures between men and women. A chapter is devoted to Blau’s research.

Strohmaier, Brigitte, and Robert Rosner. Marietta Blau, Stars of Disintegration: Biography of a Pioneer of Particle Physics. Riverside, CA: Ariadne, 2006. Print. Examines Blau’s life from childhood, focusing on her work in particle physics and her published papers.