Mark Thiemens is Dean of the Division of Physical Sciences and Distinguished Professor of Chemistry at the University of California, San Diego, and works on studies of the physical chemistry of mass independent isotope effects and their observation in nature

1. What made you want to be a chemist?

I was deeply interested in understanding basic chemistry and physics and in using this fundamental knowledge to understand nature in a large way. In the best of all possible worlds, the research would involve field work that utilizes field measurements and application of new chemical principles to better understand nature . I have been fortunate in that our study of basic physical chemical laws of isotope effects has allowed me to work at the South Pole, Greenland Summit, Tibetan Himalayas, rain forests in South America and South East Asia as well as to collect samples from ships in the major oceans, and to fly rockets and balloons for atmospheric sampling. Analysis of meteorites and lunar samples for solar system evolutionary studies has added an extra-terrestrial component to my “field work”.

2. If you weren’t a chemist and could do any other job, what would it be – and why?

If I wasn’t a chemist I wouldn’t stray too far away, and would likely be a pure geochemist or physicist instead.

3. What are you working on now, and where do you hope it will lead?

Projects in the laboratory at present include collection and analysis of samples from a snow pit in the Antarctic to study temporal changes in the oxidation state of the planet over time, extraction of water from meteorites and Mars samples to understand the origin and evolution of water in the solar system, detection of atmospheric radioactive ³⁵S to detail the situation at Fukushima and use the emissions to clock long range transportation of aerosols across the Pacific Ocean, measurement of the oxygen isotopic composition of the solar wind from the return samples of the Genesis mission, theoretical understanding of the physical chemistry of photodissociation of molecular nitrogen and CO, and experimental isotopic studies of the early process of gas to particle formation at the earliest stage of the solar system formation.

4. Which historical figure would you most like to have dinner with – and why?

This was very hard to answer. Ultimately I chose Thomas Jefferson, an interest that dates back to my visit to Monticello as a teenager. I was deeply impressed with his studies of science, which range from meteorology, to geology and paleontology, interest in meteorites (such as the Weston meteorite and the associated controversy), and his meticulous notes on nature, which includes chemically related phenomena. As an educator, his central role in the founding of the University of Virginia and working on the new curricula, and architecturally designing the Rotunda is unprecedented. If one throws in his composition of the Declaration of Independence, and the fact that that he was the only President who was a scientist, there likely would be no lack of conversation over dinner. To quote President Kennedy when hosting a dinner for a number of Nobel Laureates at the White House “I think this is the most extraordinary collection of talent, of human knowledge, that has ever been gathered at the White House – with the possible exception of when Thomas Jefferson dined alone”.

5. When was the last time you did an experiment in the lab – and what was it?

Last summer I prepared a set of samples for short UV photolysis of metals to investigate photochemical isotope effects and to resolve potential isotope effects associated with different nuclear properties.

6. If exiled on a desert island, what one book and one music album would you take with you?

For the book, I am pilfering a comment of my son Max who suggested that a first rate astronomy book would allow me to study the stars and their migrations every night and to really learn the night sky. For an album, I would find an album of Mozart that begins with his first symphonic composition and ends with his last to allow me to enjoy the complexity of the individual pieces as well as the evolution through his life.

7. Which chemist would you like to see interviewed on Reactions – and why?

I am afraid to answer this because I would leave out the many other chemists that I would like to see interviewed.