April 5, 1887 (Wroclaw-Wroclaw, Poland) – November 26, 1964 (Durham, United States).
Hedwig Kohn, the daughter of German Jews, was born in the city of Wroclaw (German Empire, today Poland) on April 5, 1887. Her father, Georg Kohn, was a wholesaler of fine fabrics and her mother, Helene Hancke, was a member of a wealthy family,
A year before women could officially enroll, Kohn was admitted as an auditor in the physics department at the University of Wrocław. Finally, because the situation changed, she was able to graduate and even get her doctorate in physics in 1913.
Otto Lummer, known for the precision measurements of radiation that contributed to the formulation of Planck's radiation law, was her adviser and made her his assistant in 1914. After years of teaching and research, and great doses of patience, she received college habilitation in 1930. In this way, Kohn, Meitner, and Sponer became the three women to qualify to teach physics before World War II.
However, she could make little use of said authorization since in 1933 she was removed from her post for being Jewish. A hard stage began here for Kohn who, in 1935, took advantage of US funding to move to Arosa (Switzerland). she and she contribute to the study of the measurement of the intensity of ultraviolet light from the sun at the Licht-klimatisches Observatory. During her three-month stay in Switzerland she did not get a permanent job, so she had to return to Wroclaw.
The "Night of the Crystals" (November 9, 1938) made clear the urgent need to emigrate and flee Nazi Germany as soon as possible. However, that was not feasible without a job offer in another country. It was Rudolf Ladenburg, who directed Kohn's doctoral research, who tried to help her by getting her a job at the University of Aberdeen for the winter of 1939. Ladenburg was then a highly respected physicist at Princeton University and managed to mediate so that through the International Federation of University Women and the Society of Science and Learning of London a job for Hedwig could be obtained.
However, the outbreak of the war caused England to immediately cancel all work visas granted. Kohn, along with two other women, Lise Meitner and Hertha Sponer, who found themselves in the same situation: they needed to flee Nazi Germany and start their lives from scratch abroad.
Many were the letters that Kohn, Ladenburg, Meitner and Sponer exchanged with the representatives of the International Federation of University Women and various universities around the world. They finally got three places in the United States for the three of them with a total duration of one year: at the School for Women at the University of North Carolina, at Sweet Briar College in Virginia and at Wellesley Collette in Massachusetts. This good news offered Kohn a middle course with obtaining a visa to go to Sweden in 1940, until she obtained a visa for the United States and settled there permanently.
After her stay in Sweden, Kohn left Stockholm for Greensboro (North Carolina) on October 12, 1940. The journey was long and hard, arriving at her destination two months after she was seriously ill. She was unable to return to work until January 1941 after a recuperative stay with James Franck in Chicago and later with Hertha Sponer in Durham.
Hedwig Kohn spent a year and a half in Greensboro before taking her position at Wellesley, where she became a highly regarded professor, won a university research award, and remained there until her retirement in 1952. While at Wellesley, she created a modest research laboratory for flame emission spectroscopy that served to introduce students to research. In 1952, the government of the Federal Republic of Germany awarded her a pension and the title of emeritus professor.
After her retirement, she conducted independent research as an associate at Duke University for twelve more years, continuing to direct the work of doctoral students and select other postdocs to study flame spectroscopy with her, measuring the characteristics of absorption and concentrations of most atomic species in flames. This work was basically a continuation of the one she carried out forty years earlier (between 1912 and 1933).
Kohn worked in the field of quantitative measurement of radiation intensity, and he contributed to atomic and molecular spectroscopy, primarily in work involving quantitative measurements of luminosity or temperature. She wrote several chapters, totaling more than two hundred pages, in a major physics textbook, Mueller-Pouillets Lehrbuch der Physik, 1929. Her contributions to textbooks on radiometry, the measurement of visible light radiation intensity and flame emission temperature remained the standard introduction to the field well into the 1960s.
Hedwig Kohn died in 1964 at the age of 76, being active in her research and always surrounded by students.
