It almost ranks as a milepost of youth - you get together with a friend, turn the lights out and thrown a blanket over your heads so that one of you can watch while the other chomps into a Wint-O-Green Lifesaver, hoping to see the fabled spark that occurs when certain crystals are exposed to sudden breaking pressure. That phenomenon is called triboluminescence, and though demonstrating it is within the grasp of elementary students, the actual physics behind it is still a matter of some debate.
We received our first guidance into what factors cause certain materials to spark when they break, and others to glow when exposed to radiation, from the research of Frances Gertrude Wick (1875-1941). She was one of seven children born to Alfred and Sarah Ann Wick between the years of 1862 and 1879 in Butler County, Pennsylvania. Alfred was an innkeeper somehow turned local oil impresario who made sure that his daughters had whatever education they desired. Both Frances and her sister Sarah began attending Wilson College in 1893, and graduated in 1897.
Physics had yet to meaningfully enter Frances’s life, and after graduation she settled into one of the few professions reliably open to a woman of college education in the late 19th century - that of high school teacher. She worked at Butler High School for a monthly $45 wage (to give some comparison, if you were a bricklayer in Philadelphia in 1897 you could expect a monthly wage of $76, while a blacksmith brought in $43, and a general laborer about $31.50). All went smoothly until she was informed that, the following year, she would be expected to teach physics, a subject about which she knew next to nothing. She knuckled up to the task before her, taking a summer course in physics and sacrificing sleep to fill her head with the subject more thoroughly, finding along the way that she genuinely enjoyed the subject, and would like to make a go of it as a career.
Her family supported the decision, and in 1904 Wick matriculated at Cornell, earning a bachelor’s in physics by 1905, a master’s by 1906, and a PhD by 1908, a stunning pace of self-development made possible by her own disciplined approach to learning and by the encouraging presence of Edward Leamington Nichols (1854-1937), a rigorous experimentalist who very literally wrote the book on lab procedure (in 1894 he authored the two volume Laboratory Manual of Physics and Applied Electricity, followed in 1896 by the three volume The Elements of Physics: A College Text-book), and who was known in his time as a particular advocate of women as scientists. His research centered around luminescence and fluorescence, phenomena which Wick would make the center of her own studies. What made certain substances glow, and how did exposure to different conditions affect the duration and intensity of the effect?
Nichols supported Wick throughout her time at Cornell, fostering her natural talent as an experimentalist which led to the publication of her first papers on the fluorescence of resorufin, a bright pink compound with fluorescent effects visible to the naked eye. She investigated questions of when resorufin was most amenable to absorbing radiation, and though a half decade later her results were found to be the result of a defect in her equipment, it was nonetheless the start of a powerful career.
Wick took a break from fluorescence for her PhD work on the insistence of Nichol, whose view was that the exposure to other parts of physics would be good for her professional development. Her PhD dissertation, therefore, was on “Some Electrical Properties of Silicon,” which attempted to make headway in the tricky task of getting silicon to interact with other materials, in addition to investigating the role that purity played in silicon’s conductive properties, questions which were eventually at the center of silicon’s starring role in the semiconductor revolution a half century later.
Her PhD obtained, Wick took up a teaching position first at Simmons College (1908-1910), and then at Vassar (1910-1940). Here, she carried on her own research into the fluorescence of some twenty different uranium compounds while also collaborating with her close friend and fellow Cornell student of Nichols, Louise S. McDowell (1876-1966). During World War I, her expertise on luminescence was tapped by the war effort in the development of new gun sights. Her work in the 1920s consisted in nailing down the precise optimal conditions for obtaining significant and long-lasting luminescent effects of halogen salts, synthetically prepared materials, rare earth salts, fluorite, and ozone, including their reactions to exposure to different wavelengths of electromagnetic radiation, to pure samples of radium, to neutron and electron bombardment, and to different conditions of temperature and pressure. This was difficult work to carry out with the materials she had at hand, and though every so often a lucky break would come in the form of short-term access to more sophisticated facilities at Harvard, the Cavendish, or the Radium Institute of Vienna, for the most part she was on her own, developing clever techniques that would allow measurement of luminescence via microphotometers and visual inspection.
In the 1930s, she began her experiments in the conditions underlying triboluminescence, investigating how the same factors that played a role in regular fluorescence might or might not have a part to play in the intensity of triboluminescent phenomena. She studied crystals of ice and sugars, and was able by 1939 (the same year she both made the papers with her demonstration that ice can indeed emit light and was made chair of Vassar’s physics department) to isolate three different species of triboluminescent effects, including the famous “spark” effect of all our middle school night-time experiments, harnessing the new theories of quantum mechanics to hypothesize that a subtle ballet between thermal, mechanical, and radiation events could be the source of the energy that allowed electrons to transition between different energy levels and give off light. (Today, some 85 years later, the phenomenon is still not completely explained, and physicists continue, like Wick, to chalk it up to a combination of energy suddenly imparted by the physical stress of Hitting Things Very Hard With Hammers, the existence of asymmetries and impurities in crystals that allow for sudden separation of charges that both release light when they recombine and ionize the air around them, allowing for electrical discharge events.)
Over the course of her thirty year academic career, she built up a reputation for the utter reliability of her experimental procedures, and was recognized accordingly. She was made a fellow of the Optical Society, the American Physical Society, the American Association for the Advancement of Science, and the Association of College Professors, and a number of her results made their way into the popular press in the 1930s, while her professional papers set the standard for decades on the characterization of luminescent phenomena. For the last fifteen years of her life, she lived comfortably in a house near Vassar she shared with the same sister she had begun her academic adventure with, back in 1893. She passed away on June 15, 1941, in Poughkeepsie, New York, after an illness of several months. Her friend Louise McDowell would survive her by a quarter of a century, writing in August of 1941 the Wilson Alumnae Quarterly obituary which remains today virtually the only source we have about Wick’s personal life.
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