|Fig. 1: A picture of Harriet Brooks. (Source: Wikimedia Commons)|
Harriet Brooks (Fig. 1) was a nuclear physicist with important accomplishments, yet few people know her. She was born in 1876 in Ontario, Canada. In 1901, she graduated from McGill University in Canada and was not only one of a few women attending university but also one of the first to receive a Master's degree from McGill. During her college career, she was often at the top of her class in both general and honors studies, even winning prizes in physics, math, and German. 
After graduation, Brooks did a short fellowship with J. J. Thomson at the Cavendish Laboratory in Cambridge, England and then returned to McGill in 1903 to do research with her former mentor and graduate supervisor, Ernest Rutherford, in the then new field of nuclear science. With Rutherford, she was one of the first discoverers of the element radon. She studied the emanation from thorium and used a diffusion method to determine that it was a radioactive gas (radon) with a molecular weight of 40 to 100. She also helped show that uranium emits beta rays and alpha particles when decaying and that beta rays are negatively charged particles. 
In 1906, she went to work at the Curie Institute in Paris with Marie Curie and Andre Debierne. It is interesting to note that she worked with three Nobel laureates.  Here, she discovered the quantum phenomenon of atomic recoil and was the first person to figure out that one element could change into a different element. Rayner-Canham calls her most crucial work her "identification of the multiple decays taking place in sequence starting with radium, uranium, and thorium." 
In addition to her role as a researcher, Brooks was also a lecturer at Royal Victoria College, Bryn Mawr College, and Barnard College.  At Barnard, when she announced she was engaged to be married, administration asked her to resign because "according to the mores at the time, [women in academia] had to be of good Christian character and not only single but in no danger of marrying."  In a response letter to the dean, Brooks wrote, "I think it is a duty I owe to my profession and to my sex to show that a woman has a right to the practice of her profession and cannot be condemned to abandon it merely because she marries. I cannot conceive how womens colleges, inviting and encouraging women to enter professions can be justly founded or maintained denying such a principle."  In addition to being discredited simply because she wanted to get married, she was largely ignored in academic circles and history though she published many papers. 
Since her death at age 56, Brooks has since been acknowledged as Canada's first female nuclear physicist. Discoveries have rightly been attributed to her, and her role as "the most pre-eminent woman physicist in the department of radioactivity [next to Madame Curie]," as Rutherford wrote in her obituary, is finally being realized.
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 M. F. Rayner-Canham and G. W. Rayner-Canham, Harriet Brooks: Pioneer Nuclear Scientist (McGill-Queens University Press, 1992).
 M. Rossiter, Women Scientists in America: Struggles and Strategies to 1940 (Johns Hopkins University Press, 1984), pp. 15-16.