Bowen was born in
Seneca Falls, New York in 1898 to Philinda Sprague and James Bowen. Due to frequent moves of his family he was home schooled until his father died in 1908. From that point on he attended
Houghton College where his mother worked as teacher. After graduation from high school in 1915 Bowen stayed at the junior college of Houghton College, and later joined
Oberlin College from which he graduated in 1919. During his time at Oberlin, Bowen did some research on the properties of steel for the scientist
Robert Hadfield. Their results were published in 1921. Bowen began studying physics at the
University of Chicago in fall 1919. By 1921 he took a position in the research group of
Robert Andrews Millikan. He was assigned to do
ultraviolet spectroscopy of chemical elements. Millikan was persuaded by
George Ellery Hale to move to the
California Institute of Technology in 1921 and Bowen moved with him. The contact with Hale enabled Bowen also to work at the
Mount Wilson Observatory and the
Palomar Observatory. Bowen gave lectures on general physics at Caltech and did research on cosmic rays and followed his studies on UV spectroscopy. He also did calculations on spectra for the light elements of the
periodic table. With that data and the inspiration from a chapter on
gaseous nebula and the emission of radiation at low density in the book
Astronomy by
Henry Norris Russell,
Raymond Smith Dugan and
John Quincy Stewart he achieved his best known discovery. The green emission lines of the
Cat's Eye Nebula at 4959 and 5007
Ångström were discovered by
William Huggins in 1864. Because no known element was showing these emission lines in the experiment it was concluded in the late 1890s that a new element was responsible for that lines, it was called
nebulium. Bowen was able to calculate the
forbidden transitions of
doubly ionized oxygen to be exactly where the lines had been found. The low probability for collisions in the nebula made it impossible for the oxygen to get from the excited stated to the ground state and so the forbidden transitions were the main path for the relaxation. Bowen published his findings in 1927 and concluded that nebulium was not really a
chemical element. Bowen was the first director of the
Palomar Observatory, serving from 1948 to 1964. Before his retirement in 1964 and even afterwards Bowen was involved in the improvement of the optical design of several large optical instruments, for example the 100 inch
Irenee duPont at the
Las Campanas Observatory. He is also known in the context of meteorology for the introduction of the
Bowen ratio, which quantifies the ratio of sensible to latent heat over an evaporating surface. ==Honors==