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Arthur Adel died of cancer, September 13, 1994 in Flagstaff, AZ, at age 85. Art was born of immigrant parents November 22, 1908 in Brooklyn, NY, and when they moved to Detroit, he graduated from a technical high school, learning the mechanical arts that later sustained him as one of the country's leading experimental astrophysicists.
At the University of Michigan, Ann Arbor, he received a Bachelor's degree for a double major in mathematics and physics, and received vital assistantships and fellowships from the university during the depression years. He repaid these trusts throughout his life with scholastic achievement and a loyalty to the university that extended far beyond his Ph.D., awarded in 1933. His theoretical dissertation, "The Infrared Spectrum and the Structure of the Carbon Dioxide Molecule," together with a sound background in experimentation and instrumentation, equipped him with guidelines and framework for his later experimental investigations.
In 1933, Art Adel's mentor, Harrison M. Randall, chairman of the Physics department, authorized him to work jointly with the university and Lowell Observatory. It was a major turning point in his career. Earlier, Rupert Wildt had discovered the presence of ammonia and methane in the atmospheres of the major planets. Adel, using Slipher's spectra, was able to show that the absorption bands were due to harmonics of the fundamental vibrations of the methane and ammonia molecules.
Art had to do one of two things, calculate all possible harmonics of the fundamental vibrations of methane, or photograph the methane spectrum at atmospheric depths where these harmonics would manifest. He did both! This work was described in a series of papers between 1934 and 1935, appearing in Nature 134 , p. 148; Physics Rev. 46 , pp. 240,902; 47 , pp. 651, and 787. Henry Norris Russell commented, "The proof by Adel ... is as beautiful an application of spectroscopic theory as one could desire to see." (Russell, H.N., M.N.R.A.S. , 95 , 610, 1935).
While living in Ann Arbor Dr. Adel met Catherine Backus, a student majoring in mathematics and French. He and Catherine were married in 1935.
In the 1935-36 academic year, he took a leave of absence from Lowell Observatory and was a post-doctoral fellow at Johns Hopkins University. He taught evening classes in astronomy and worked with Gerhard Dieke on the hydrogen spectrum. Some of his fondest memories there were times spent with the distinguished experimental physicist, A.H. Pfund.
The Adels moved to Flagstaff in 1936 for residence at Lowell Observatory. The high and dry climate of Flagstaff became a major element in Art's successful study of the water vapor related parameters in the earth's atmosphere. His accomplishments during the years at Lowell are recorded in over fifty publications. For the listing below, I am grateful to have a history prepared by Monica A. Joseph, Boston University 1976, entitled, "The Contribution of Arthur Adel To Astronomical Infrared Spectroscopy."
Some of the major results include: (a.) the first precise definition and delineation of the rock-salt prismatic solar-telluric spectrum for 5 microns to 13.9 microns; (b.) the discovery of atmospheric nitrous oxide, the now widely accepted explanation that the origin of atmospheric nitrous oxide comes from the soil and oceans of the earth and the importance of this process as part of the Nitrogen Cycle; (c.) the discovery of atmospheric heavy water-vapor, HDO; (d.) atmospheric transmission as a function of water-vapor content from 5 to 14 microns; (e.) observations and preparation of the first grating map of the solar-telluric spectrum; (f.) the discovery of the 20 micron window in the earth's atmosphere; (g.) and the first definitive emission spectrum of the moon, with evidence that it radiates as a simple black body.
In 1942 Adel joined the war effort and did research for the Navy. From 1942-46, he taught physics at the University of Michigan, and during 1946-48 was assistant professor of astronomy at the McMath-Hulburt Solar Observatory.
While at Michigan he worked under a government contract to establish an infrared laboratory at Hollomon Air Force Base (Alamogordo, NM). While there, he investigated radar's failure to deliver energy at specific wavelengths. Van Vleck, Uhlenbeck, and Dennison suggested the intrinsic width of a water vapor line might cause the problem. Art reworked all his equipment, installed a new grating and the exceedingly narrow bandpass was measured. He solved the problem.
In 1948 Adel accepted a professorship at Arizona State College, now Northern Arizona University (NAU), Flagstaff, AZ, where he taught mathematics and continued his atmospheric infrared research.
With an Air Force contract he established the Atmospheric Research Observatory on campus, in order to continue his study of atmospheric ozone. A 24-inch reflector was equipped with a rock-salt prism monochromator, and a prism-grating monochromator was fed from a 16-inch coelostat. Observations began in 1952 and continued into the next decade. With E.S. Epstein, Adel determined the vertical atmospheric ozone distributions from absorptions and radiation by ozone. During their ozone research, they discovered ten and eighteen day temperature periodicities in the stratosphere and a corresponding eighteen day period in the troposphere.
Dr. Arthur Adel retired as professor emeritus in May 1976, and in 1982 the NAU mathematics building was named in his honor. He was very proud of his students and one informed me Adel inspired them to pursue advanced degrees, and watched over them with guiding care.
He was a co-founder and first president of the NAU's chapter of Sigma Xi, he was elected in 1970 to honorary membership in Sigma Pi Sigma (the national physics honor society), and was a fellow of the American Physical Society and the Arizona Academy of Science. In 1977 he was named a Fellow of the Explorers Club, and the following year he was elected to the Johns Hopkins University Society of Scholars. He received a certificate from the American Astronomical Society acknowledging his fifty years of membership in 1994.
A few weeks before his death we talked about the Comet Shoemaker-Levy impact with the planet Jupiter. He told me that in the 1930's he had mentioned to V.M. Slipher that the large white spots on Saturn might be cometary impacts. He was amused, in his impish way, that the excitement we experienced during the SL-9 impact, has been available to astronomers and the public for decades.
In retirement, Art took fastidious care of Catherine, his love of sixty years. He attended many of the numerous scientific functions and lecture series held in the Flagstaff community. Visitors were always impressed with the questions from the dapper, gentle man with impeccable manners. Art's persistent probing mind was a stimulation to his students, colleagues and vast number of friends. We miss him.
Obituary written by: Richard L. Walker (U.S. Naval Observatory, Flagstaff, Arizona)
BAAS Citation: BAAS, 1994, 26, 1600
SAO/NASA ADS Bibcode: 1994BAAS...26.1600W