William Weber Coblentz: American Physicist and Pioneer of Infrared Spectroscopy

W. W. Coblentz was one of the preeminent researchers in the field of infrared spectroscopy with work spanning a broad range of physics, chemistry, spectroscopic theory, instrumentation, applications, and sample handling. The Coblentz Society was established in his name in 1954 by Norman E. Wright and Van Zandt Williams.

William Wallace Coblentz, (portrait right [1]), born on November 20, 1873, in North Lima, Ohio, emerged as an unlikely pioneer in the field of spectroscopy, and has left an indelible mark on infrared spectroscopy with his unwavering curiosity, tenacity, and groundbreaking research (2). Despite the humblest of beginnings, marked by personal loss and financial hardship, Coblentz’s drive, focus, and tireless dedication has made him one of the most prominent figures in the interdisciplinary combination of physics, astronomy, and spectroscopy.

Photo of W. W. Coblentz, Attribution: Harris and Ewing, National Bureau of Standards, courtesy AIP Emilio Segrè Visual Archives (ref. 1 in literature).

W. F. Meggers, another icon of spectroscopy, wrote, “There is no doubt that William Weber Coblentz was the principal pioneer in radiometry and infrared spectroscopy. No one else has ever equaled his output of radiometers or observations by their means.” He said, “When funds were denied, he often took cash from his pocket to buy materials and instruments” (3).

Coblentz’s life journey into the world of academia was most unconventional, and was characterized by shear abilities, fortitude, and perseverance fueled by an unyielding pursuit of knowledge. Raised by his father, David, alongside his younger brother, Oscar, Coblentz faced early adversity with the loss of his mother, Catherine, when he was barely three years old. Financial constraints further complicated his path, as the family lived on farms without ever owning one, necessitating laborious efforts just to make ends meet. However, these challenges did not deter Coblentz’s curiosity and drive for understanding and knowledge of the world around him, and he pursued informal learning and formal education with resolute determination.

Early Career

His academic journey began with a delayed start, as he completed his high school education in 1896 at the age of 22. Eager to pursue further studies, Coblentz initially enrolled at Cornell University, but, constrained by financial limitations, he switched to the local and more affordable Case School of Applied Science in the same year. This decision marked the beginning of a path that would greatly influence his illustrious career. Despite the delayed start, Coblentz demonstrated remarkable academic prowess, graduating with a Bachelor of Science degree in physics in 1900 at the age of 27 (2). Initially pursuing an electrical engineering major, he later shifted to physics to accommodate his growing fascination with astronomy, a subject not covered in the engineering curriculum, allowing him to formally pursue his newfound passion for the stars.

Coblentz had attracted the attention of his professors at Case, and Dayton C. Miller, a famous physicist from Case, coached Coblentz to pursue an advanced degree. Taking his advice, Coblentz was led back to Cornell University in September 1900, where he continued his pursuit of theoretical physics under the advisement of Ernest G. Merritt and Edward L. Nichols, heads of the physics department. These mentors suggested that Coblentz begin work in the fledgling new field of infrared (IR) absorption spectroscopy, which at that time was not really a field, but more of a curiosity, since in 1900 only a few crude infrared spectra existed as measured up to 5.0 µm (micrometers) (2). In today’s framework the near-infrared region refers to the spectral region of 0.78 to 2.5 micrometers (10^-6 m), while mid-infrared is generally considered to be represented by the spectral region of 2.5 to 50 micrometers.

Coblentz soon demonstrated his mechanical and optical ingenuity, as well as his legerdemain, by constructing a crude but effective radiometer-based detection system to measure infrared radiation from a small footprint spectrometer using a dispersion element consisting of a rock salt prism. This surprised his faculty mentors, and soon drew attention to his original work, since he was able, for the first time anywhere, to measure infrared spectra up to 15 micrometers. On the basis of this remarkable achievement, his MS degree was granted in June, 1901, and his PhD in June, 1903 (2). The title of his thesis was “Some Optical Properties of Iodine,” and the work was published as a three article series in the journal Physical Review in 1903 (4–6).

Continuing encouragement for the talented and dedicated young graduate physicist, Edward Nichols recommended Coblentz for an Honorary Fellowship research position at the Cornell physics department for the years 1903 to 1905. This was funded by the Carnegie Institution of Washington, with a stipend of $1000 per year (the equivalent to just over $35,000 in 2024). For those two years, the newly minted PhD dedicated himself to accurately, and manually, measuring the infrared spectra of several thousand compounds; a feat requiring 12 to 15 hours per day over the duration of his fellowship (2).

Career at National Bureau of Standards

Nichols continued to mentor the young Coblentz and encouraged him to dedicate his life to the pursuit of research. In 1904 the newly organized National Bureau of Standards (NBS) in Washington, D.C. was forming their various departments and Nichols suggested Coblentz apply. After taking the Civil Service exam Coblentz was hired in May, 1905 as a laboratory assistant to Samuel W. Stratton, who just happened to be the first NBS Director, at a salary of $900 per year ($31,500 today), Coblentz took his position on the ground floor of the Physics building and remained in the same corner room in this building until 1945 (2).

At NBS, Coblentz became the founder of their radiometry laboratory and began to make many infrared spectra measurements of gases, liquids, and solids for organic and inorganic compounds, and metals. IR spectra were measured in absorption, transmittance, reflection modes and geometries. His early publications involved radiometric investigations of infrared absorption and reflection spectra of many materials, studies of the Nernst glower (infrared radiation source), and various issues associated with infrared measurements and instrument detection designs. In his initial work in 1905, Coblentz compared the various approaches for making infrared measurements including the thermopile, Nichols (Crookes) radiometer, metal-strip bolometer, and radiomicrometer. He reported and published this work in 1906 (7).

Coblentz’s work supervisor at NBS, S. W. Stratton, requested that Coblentz shift his work emphasis to the study of black body radiation (Kirchhoff’s law of thermal radiation [8]), a popular subject of research in European physics circles at the time. This research resulted in a set of papers published on multiple aspects of the phenomenon (9–13). It was eventually described more completely by Planck’s law in 1914 (14), and later by the theory of quantum mechanics. It may have been Stratton’s wish that Coblentz’s work could lead to a more fundamental understanding thermal radiation such as that described by Planck.

In 1924, Coblentz, in the middle of his career at NBS, and at the age of 51, married 27-year-old Catherine Emma Cate (1897-1951) from Hardwick, Vermont. From all indications, Catherine Cate Coblentz was a soothing and charming addition to Coblentz’s life (3). One can imagine William pouring over his data and spectra in the evenings, while Catherine wrote her literary works. She became a well-known American writer, best remembered for her children’s books published from 1936 to 1950. She received acclaim as a Newbery Honor laureate (1950) and a Lewis Carroll Shelf Award winner (1958) for her children’s story The Blue Cat of Castle Town (15,16). They had spent their honeymoon at Lowell Observatory in Flagstaff, Arizona, where Catherine wrote her first children’s book Animal Pioneers, which would be published in 1936, while Coblentz made astronomical studies (3).

Infrared Astronomy

Coblentz’s scientific contributions involved basic research in a broad range of scientific pursuits, including IR astronomy, where in 1914 he was prepared to measure the “heat from the stars” (2). At the urging of Stratton, he had written to George E. Hale, director of Mount Wilson Observatory, about using the then-largest telescope in the world for these measurements, that being the 60-inch reflector. (The 100-inch Hooker Telescope on Mount Wilson was not available for astronomical observations until 1917.)

Coblentz was however successful in his endeavor to measure the IR spectra (heat) of stars and planets as he made his measurements over eighteen nights using the Crossley 36-inch reflector at the Lick Observatory on Mt. Hamilton in California. He was able to measure 110 stars down to magnitude 6.7, as well as the planets Jupiter, Venus, and Mars. This work impressed astronomer Seth B. Nicholson, who initiated these radiometric measurements for the 100-inch Mt. Wilson reflector in 1922.

Coblentz, with Carl Otto Lampland, pursued his stellar, planetary, and ultraviolet (UV) solar radiation studies using the 42-inch reflector at the Lowell Observatory in Flagstaff, Arizona for multiple observing sessions over the years 1921 to 1938. Coblentz and Lampland also measured the day and night temperatures on Mars, indicating the existence of a Martian atmosphere (17). The 42-inch telescope was later named the Lampland telescope and is now retired. Coblentz has craters on Earth’s moon and Mars named after him (18,19).

Legacy of Spectroscopic Contributions

Coblentz’s work has had a meaningful and enduring impact on infrared spectral interpretation, instrumentation and detectors, as well as IR theory and applications. In addition to his work in IR spectroscopy and astronomy, Coblentz made significant contributions to the study of the photoelectric properties of matter published in numerous research papers and government reports (20). He researched the methods of measuring UV radiation (21) and the health related aspects of UV radiation exposure (22,23). He also did work in bioluminescence (24) and atmospheric ozone (25). A further summary of Coblentz’s scientific and spectroscopy contributions compiled in 1962 is given in reference (26). William F. Meggers published a summary of the life of Coblentz, based on Coblentz’s autobiography in 1967. This comprehensive work lists a chronology of Coblentz’s publications and patents and it readily available online (3). Additional biographical sources are found in references (27–30).

Coblentz received significant honors for his outstanding contributions to spectroscopic research, including the H. N. Potts medal of the Franklin Institute, in 1910; the Jannsen medal of the French Academy of Sciences in 1920; and the John Scott medal of the City of Philadelphia, in 1924. He received the gold key of the American Congress of Physical Therapy, in 1924; membership in the National Academy of Sciences, in 1930; the Rumford medal of the American Academy of Arts and Sciences, in 1937; and the Optical Society of America Frederic Ives medal for distinguished work in optics in 1945. The Society for Applied Spectroscopy honored him with its gold medal in 1953. In 1954, the Coblentz Society was established to foster the understanding and application of vibrational spectroscopy, and the society awarded its inaugural medal to Coblentz.

Coblentz’s many contributions to the broad field of infrared spectroscopy have been inspirational for new generations of scientists and researchers. His passion for learning and dedication and focus for research remain a shining example for aspiring and experienced scientists and scholars worldwide. Though he passed away at age 88 in 1962, Coblentz’s legacy lives on, a testament to the enduring impact of his extraordinary life and work. Megger’s concludes his biography of Coblentz with, “Most of his last decade he lived in seclusion with flowers, birds, and chipmunks…and enjoying memories revived by periodic visits of his old friends from the National Bureau of Standards and elsewhere” (3). We can surmise that Coblentz’s research and work ethic live on in today’s vibrant spectroscopic research community.

References

1. Photo of W. W. Coblentz, Attribution: Harris and Ewing, National Bureau of Standards, courtesy AIP Emilio Segrè Visual Archives - https://repository.aip.org/islandora/object/nbla%3A292944 (accessed 2024-03-04).
2. Coblentz, W. W. From the Life of a Researcher (autobiography); Philosophical Library, Inc., 1951. 238 pp. (Ibid., pp. 153-54).
3. Meggers, W. F. William Weber Coblentz, 1873–1962. A Biographical Memoir; National Academy of Sciences, Washington D.C., 1967 https://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/coblentz-william-w.pdf (accessed 2024-03-01).
4. Coblentz, W. W. Some Optical Properties of Iodine. Phys. Rev. (Series I) 1903, 16 (1), 35. DOI: 10.1103/PhysRevSeriesI.16.35
5. Coblentz, W. W. Some Optical Properties of Iodine. II. Phys. Rev. (Series I) 1903, 16 (2), 72. DOI: 10.1103/PhysRevSeriesI.16.72
6. Coblentz, W. W. Some Optical Properties of Iodine. III. Phys. Rev. (Series I) 1903, 17 (1), 51. DOI: 10.1103/PhysRevSeriesI.17.51
7. Coblentz, W. W. Note on a New Form of Radiometer. Phys. Rev. (Series I) 1906, 22 (6), 358. DOI: 10.1103/PhysRevSeriesI.22.358
8. Kirchhoff, G., Translated by Guthrie, G. On the Relation Between the Radiating and Absorbing Powers of Different Bodies for Light and Heat. Phil. Mag. Series 4 1860, 20, 1–21.
9. Coblentz, W. W. Infra-Red Emission Spectra. Phys. Rev. (Series I), 1906, 22 (1), 1. DOI: 10.1103/PhysRevSeriesI.22.1
10. Coblentz, W. W. Radiation from Selectively Reflecting Bodies. Phys. Rev. (Series I) 1907, 24 (3), 307. DOI: 10.1103/PhysRevSeriesI.24.307
11. Coblentz, W. W. Selective Radiation from the Nernst Glower; U.S. Government Printing Office, 1908. https://nvlpubs.nist.gov/nistpubs/bulletin/04/nbsbulletinv4n4p533_a2b.pdf
12. Coblentz, W. W. Instruments and Methods Used in Radiometry; Vol. 4. No. 3. U.S. Government Printing Office, 1908.
13. Coblentz, W. W. Radiation Constants of Metals. No. 105; U.S. Government Printing Office, 1909.
14. Planck, Max. The Theory of Heat Radiation; Blakiston, 1914. https://www.gutenberg.org/files/40030/40030-pdf.pdf
15. Association for Library Service to Children John Newbery Medal Home Page. https://www.ala.org/alsc/awardsgrants/bookmedia/newbery (accessed 2024-03-04).
16. Library Thing Lewis Carroll Shelf Award Home Page. https://www.librarything.com/award/366/Lewis-Carroll-Shelf-Award (accessed 2024-03-04).
17. Coblentz, W. W.; Lampland, C. O. United States. Further Radiometric Measurements and Temperature Estimates of the Planet Mars; 1926. Washington, D.C.: U.S. Dept. of Commerce, Bureau of Standards, 1927. https://nvlpubs.nist.gov/nistpubs/ScientificPapers/nbsscientificpaper553vol22p237_A2b.pdf
18. USGS Home Page. https://planetarynames.wr.usgs.gov/Feature/1256 (accessed 2014-03-04)
19. USGS Home Page. https://planetarynames.wr.usgs.gov/Feature/1257 (accessed 2014-03-04)
20. Coblentz, W. W. Various Photo-electrical Investigations. No. 462. US Department of Commerce, Bureau of Standards, 1922.
21. Coblentz, W. W. Methods of Measuring Ultra-Violet Radiation. Radiology 1928, 10 (2), 116–121. DOI: 10.1148/10.2.116
22. Coblentz, W. W. The Physical Aspects of Ultraviolet Therapy. J. Am. Med. Assoc. 1938, 111 (5), 419–423. https://jamanetwork.com/journals/jama/article-abstract/281889
23. Coblentz, W. W. Sources of Radiation and their Physical Characteristics. Cold Red Ray and Cold Ultraviolet Ray Lamps. J. Am. Med. Assoc. 1931, 97, 1965–1967. https://www.cabidigitallibrary.org/doi/full/10.5555/19322700590
24. Coblentz, W. W.; Hughes, C.W. Spectral Energy Distribution of the Light Emitted by Plants and Animals. No. 538. US Government Printing Office, 1926.
25. Coblentz, W. W.; Stair, R. Distribution of Ozone in the Stratosphere: Measurements of 1939 and 1940. J. Res. Nat. Bur. Stand. 1941, 26, 161–174. https://nvlpubs.nist.gov/nistpubs/jres/26/jresv26n2p161_A1b.pdf
26. Plyler E. K. The Scientific Contributions of William Weber Coblentz. Appl. Spectrosc. 1962, 16 (3), 73–77. DOI: 10.1366/000370262774415903
27. William W. Coblentz American Institute of Physics Home Page. https://history.aip.org/phn/11501018.html (accessed 2024-03-01).
28. The Coblentz Society Home Page. https://www.coblentz.org/william-weber-coblentz/ (accessed 2024-03-01).
29. William Coblentz Wikipedia Home Page. https://en.wikipedia.org/wiki/William_Coblentz (accessed 2024-03-01).
30. NIST, National Bureau of Standards (NBS) Home Page. https://www.nist.gov/search?s=Coblentz (accessed 2024-03-04).

About the Author

Jerome Workman, Jr. serves on the Editorial Advisory Board of Spectroscopy and is the Executive Editor for LCGC and Spectroscopy. He is the co-host of the Analytically Speaking podcast and has published multiple reference text volumes, including the three-volume Academic Press Handbook of Organic Compounds, the five-volume The Concise Handbook of Analytical Spectroscopy, the 2nd edition of Practical Guide and Spectral Atlas for Interpretive Near-Infrared Spectroscopy, the 2nd edition of Chemometrics in Spectroscopy, and the 4th edition of The Handbook of Near-Infrared Analysis. ●