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
Pieter Rijke 1836. The title of his Ph.D. thesis was "De origine electricitatis voltaicae". In 1835 he was appointed professor of physics at the Royal Athenaeum in Maastricht. In 1845 he became extraordinary professor and in 1854 he was promoted to full professor of physics at the University of Leiden. There he started a physics laboratory with a large collection of scientific instruments. His most important students were H.A. Lorentz and J.D. van der Waals. He retired in 1882, and was succeeded by Heike Kamerlingh Onnes as professor of experimental physics at the University of Leiden. Rijke became a member of the