Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist.
He graduated with a B.S. from the Columbia University School of Mines in 1903 and did postgraduate work in chemistry under Nobel laureate Walther Nernst in Göttingen and earned his Ph.D. degree in 1906.
Langmuir then taught at Stevens Institute of Technology in Hoboken, New Jersey, until 1909, when he began working at the General Electric research laboratory (Schenectady, New York). While at G.E., from 1909-1950, Langmuir advanced several basic fields of physics and chemistry, invented the gas filled incandescent lamp, the hydrogen welding technique, and was awarded the 1932 Nobel Prize for Chemistry for his work in surface chemistry.
His initial contributions to science came from his study of light bulbs (which was a continuation of his Ph.D. work). First his improvement of vacuum techniques led to the invention of the high-vacuum tube. A year later he discovered that the lifetime of a tungsten filament was greatly lengthened by filling the bulb with an inert gas, such as argon, which is an important part of the modern day incandescent light bulb.
As he continued to study filaments in vacuum and different gas environments he began to study the emission of charged particles from hot filaments (thermionic emission). He was one of the first scientists to work with plasmas and was the first to call these ionized gases by that name. He introduced the concept of electron temperature and in 1924 invented the diagnostic method for measuring both temperature and density with a thermionic probe, now called a Langmuir probe and commonly used in plasma physics. The current of a biased probe tip is measured as a function of bias voltage to determine the local plasma temperature and density.
He also discovered atomic hydrogen, which he put to use by inventing the atomic hydrogen welding process.
Following World War I Langmuir contributed to atomic theory and the understanding of atomic structure by defining the modern concept of valence shells and isotopes.
He joined Katherine Blodgett to study thin films and surface adsorption. They introduced the concept of a monolayer (a layer of material one molecule thick) and the two dimensional physics which describes such a surface. In 1932 he received the Nobel Prize for Chemistry "for his discoveries and investigations in surface chemistry."
During World War II Langmuir worked to develop protective smoke screens and methods for de-icing aircraft wings. This research led him to discover that the introduction of dry ice and iodide into a sufficiently moist cloud of low temperature could induce precipitation, allowing some degree of weather control.
He married Marion Mersereau in 1912. They had a son, Kenneth, and a daughter, Barbara.