Alexander Edgar Douglas, (12 April 1916, in

Melfort, Saskatchewan Melfort ( 2016 population 5,992) is a city in Saskatchewan, Canada, located approximately southeast of Prince Albert, northeast of Saskatoon and north of Regina. Melfort became Saskatchewan's 12th city in 1980. Melfort was formerly called ...

– 26 July 1981, in

Ottawa Ottawa is the capital city of Canada. It is located in the southern Ontario, southern portion of the province of Ontario, at the confluence of the Ottawa River and the Rideau River. Ottawa borders Gatineau, Gatineau, Quebec, and forms the cor ...

) was a

Canadian Canadians () are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of their being ''C ...

physicist, known for his work in molecular spectroscopy. He was president of the

Canadian Association of Physicists Canadian Association of Physicists (CAP), or in French Association canadienne des physiciens et physiciennes (ACP) is a Canadian professional society that focuses on creating awareness among Canadians and Canadian legislators of physics issues, sp ...

in 1975–1976.

Biography

Born on a farm in

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

, Douglas received his BA and MA degrees from the

University of Saskatchewan The University of Saskatchewan (U of S, or USask) is a Universities in Canada, Canadian public university, public research university, founded on March 19, 1907, and located on the east side of the South Saskatchewan River in Saskatoon, Saskatch ...

Gerhard Herzberg Gerhard Heinrich Friedrich Otto Julius Herzberg, (; December 25, 1904 – March 3, 1999) was a German-Canadian pioneering physicist and physical chemist, who won the Nobel Prize for Chemistry in 1971, "for his contributions to the knowledge ...

was his MA thesis advisor. During World War II, Douglas interrupted his studies to do military-related research in the Physics Division at the NRC. After the war, he earned his PhD in physics at

Pennsylvania State University The Pennsylvania State University (Penn State or PSU) is a Public university, public Commonwealth System of Higher Education, state-related Land-grant university, land-grant research university with campuses and facilities throughout Pennsyl ...

under David H. Rank. In 1949 Douglas became NRC's head of the Spectroscopy Section of the Physics Division, which was directed by Gerhard Herzberg. From 1969 to 1973 Douglas was the director of the Physics Division of the NRC. He returned to his previous job as head of the Spectroscopy Section in 1973 and remained in that position until his retirement from the NRC in 1980. A. E. Douglas was the first to observe the spectra of B₂, Si₂, CH⁺, SiH⁺, NF, PF, BN, CN⁺ and many other diatomic or triatomic molecules. He first identified the 4050 group of lines observed in comets as being due to the C₃ molecule. Using a method that he developed, Douglas made the first studies of the

Zeeman effect The Zeeman effect () is the splitting of a spectral line into several components in the presence of a static magnetic field. It is caused by the interaction of the magnetic field with the magnetic moment of the atomic electron associated with ...

in polyatomic molecules. According to Gerhard Herzberg:

One of Douglas' most important contributions was his recognition of the reason for "anomalous lifetimes," that is, the failure of a simple relationship between absorption coefficient and lifetime to account for lifetimes in such compounds as NO₂, SO₂, C₆H₆. This phenomenon, referred to in the most recent literature as the Douglas effect, is closely connected with
internal conversion Internal conversion is an atomic decay process where an excited nucleus interacts electromagnetically with one of the orbital electrons of an atom. This causes the electron to be emitted (ejected) from the atom. Thus, in internal conversion (o ...
in larger molecules.

In astrophysical applications of molecular spectroscopy, Douglas is known for his identification of interstellar CH⁺ and of cometary C₃ and for the reproduction in the laboratory of the Meinel bands of N₂⁺ and other spectra.

Honours and awards

* 1956 – Elected Fellow of the Royal Society of Canada * 1970 – Medal for Achievement in Physics from the Canadian Association of Physicists * 1979 – Elected Fellow of the Royal Society of London * 1980 – International meeting on molecular spectroscopy sponsored in June in honour of A. E. Douglas by the NRC * 1981 –

Henry Marshall Tory Medal The Henry Marshall Tory Medal is an award of the Royal Society of Canada The Royal Society of Canada (RSC; , SRC), also known as the Academies of Arts, Humanities, and Sciences of Canada (French: ''Académies des arts, des lettres et des scienc ...

References

1916 births 1981 deaths Canadian physicists University of Saskatchewan alumni Eberly College of Science alumni Fellows of the Royal Society Fellows of the Royal Society of Canada People from Melfort, Saskatchewan Spectroscopists Presidents of the Canadian Association of Physicists {{Canada-scientist-stub