Obituary of Arthur Louis (Art) Schmeltekopf

Arthur Louis (Art) Schmeltekopf, a gifted experimental physicist, died at his home in Marshall, North Carolina, on 20 August 2007. The cause was mesothelioma of the lungs, a cancer associated with exposure to asbestos.

Art was born 24 February 1932 in Kyle, Texas, and moved to North Carolina in 1988 after retiring from the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado. He received his PhD in physics from the University of Texas at Austin and spent his entire career as a member of the NOAA Aeronomy Laboratory.

Art came to Boulder in 1962 to join Eldon Ferguson and others in a new laboratory program to study atmospheric processes. During an early collaboration with Herb Broida of the National Bureau of Standards on the spectroscopy of gas discharges, Art recognized that a flowing gas discharge could be used to quantify the reactivity of discharge-produced ions and neutral species. Art constructed a flowing-afterglow apparatus that quickly became the focus of the new laboratory. The flowing-afterglow technique revolutionized gas-phase ion chemistry over the next two decades, yielding hundreds of ion-molecule reaction rate coefficients for a wide variety of reaction types. For example, the early experiments led the team to the discovery of associative-detachment reactions (A- + B —> AB + e-), which have important consequences for aeronomy and astrophysics. These reactions along with others delineated the ion chemistry of the ionosphere and established what controls the charge density in that key region. The versatility of the flowing-afterglow technique led to its adoption by several other laboratories.

One of Art’s important contributions was to lead the first experiments to measure the rate coefficient between a vibrationally excited neutral (N2) and an atomic ion (O+). Using a microwave discharge to excite N2, he showed that the rate increased by a factor of 20 for a vibrational temperature increase from 300K to 4000K. This study fostered a long collaboration on molecular spectroscopy between Art, Daniel Albritton of the Aeronomy Laboratory, and Richard Zare of Stanford University. Their work resulted in significant improvements in the determination of Franck-Condon factors for diatomic molecules and resolved discrepancies in molecular parameters found by optical and microwave spectroscopists. Their 1973 seminal paper on Rydberg-Klein-Rees potentials is still actively cited.

In the early 1970s, Art was drawn away from gaseous electronics to study the threat to the ozone layer posed by the release of chlorofluorocarbons (CFCs). Art led a team that developed a balloon-borne sampling system to bring back flasks of ambient stratospheric air. Gas-chromatographic analysis of the samples demonstrated for the first time the fall off with altitude of CFC-11 and CFC-12 concentrations above the tropopause up to 26 km. The fall off was stronger for CFC-11 consistent with the shorter stratospheric lifetime. These results provided key confirmation of the hypothesis of Sherwood Rowland and Mario Molina that the decomposition of CFCs occurs in the stratosphere, forming chlorine species that chemically destroy ozone.

In the 1980s, Art developed a visible spectrometer with a diode-array detector in order to retrieve spectral signatures from column amounts of key stratospheric constituents such as NO2 and O3. Susan Solomon led an expedition to McMurdo Station, Antarctica, in 1986 with the new spectrometer and succeeded in detecting OClO in the Antarctic ozone hole. Since OClO is a chemical intermediate in the catalytic destruction of ozone, these observations provided some of the first evidence that reactive chlorine was the cause of the ozone hole.

Art was a leader in the use of NASA high-altitude aircraft platforms to study stratospheric photochemistry and transport. He led a team with Dieter Kley and Kenneth Kelly that developed a Lyman-alpha hygrometer for the NASA U-2 aircraft. The U-2 deployed to Panama in 1979 to measure water vapor up to 20 km in the tropical tropopause region. These measurements confirmed the water-vapor minimum above the tropopause, further advancing the idea that convection could hydrate the lower tropical stratosphere. Later, Art helped initiate and organize the 1987 NASA ER-2 aircraft mission to Punta Arenas, Chile, to examine for the first time the perturbed stratospheric photochemistry occurring inside the winter polar vortex over Antarctica using in situ instrumentation.

Art was widely recognized among his colleagues as a gifted experimental physicist, capable of applying his common sense and great skills as a designer, builder and computer programmer, to create the apparatus necessary to conduct ambitious and insightful scientific experiments. He was greatly admired and respected for his boundless intellectual curiosity, his egalitarian approach to science, his kindness and generosity to others and his delightful sense of humor.

He shared his life with his wife, Kassie, and his son Ric. They often opened their home for summer gatherings attended by the laboratory staff and friends. In his spare time he was an accomplished pipe organ builder and woodworker. These few facts can only partially describe the great man and scientist that many of us had the privilege of knowing and who influenced by his words and deeds our own lives in many ways.

E. E. Ferguson(1), F. C. Fehsenfeld(1,2), D. L. Albritton(1), and D. W. Fahey(3)

(1) Retired from the NOAA Aeronomy Laboratory

(2) Now with the Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO

(3) NOAA Earth System Research Laboratory, Boulder, CO