Liquid helium of liquid water. Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes at the University of Leiden in the Netherlands. At that time, helium-3 was unknown because the mass spectrometer had not yet been invented. In more recent decades, liquid helium has been used as a cryogenic refrigerant, and liquid helium is produced commercially for use in superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), Magnetoencephalography (MEG), and experiments in physics, such as low temperature Mössbauer spectroscopy. The temperature required to produce liquid helium is low because
Tettje Clay-Jolles 1903 when she transferred to the University of Leiden. She was one of the few women who studied physics at the university. There she began her doctoral research on low-temperature physics under Heike Kamerlingh Onnes. She worked on her thesis until December 1908 when she left her studies to devote herself to her family. Clay-Jolles met and fell in love with Jacob Clay, another of Kamerlingh Onnes's students, and in 1908 the two were married. Later that year she left school to focus on her family. She spent the next twelve years raising the couple's three children. In 1920 the