Addressing Chemistry’s “Impossible” Problems

Novel forms of spectroscopy provide insights into both practical and fundamental problems

In quantum mechanics, a particle does not have classical properties like “position” and “momentum”; rather, it is represented by a wave function that assigns a complex number to each possible measurement outcome. Problematically, although the wave function is central to quantum mechanics, it is never directly observable and thus, poses an incredible challenge to characterize and understand. Dr. Robert Field, Haslam and Dewey Professor of Chemistry at Massachusetts Institute of Technology, is highly awarded for his use of high-resolution laser and microwave spectroscopy to observe the structure and intramolecular dynamics of small molecules; in his own words, Dr. Field studies “molecules behaving badly.” His research demonstrates that new classes of structural and dynamical questions can be answered by high resolution, multiple resonance spectroscopies, through the use of his unconventional models in order to address problems previously thought to be intractable. In fact, his novel forms of spectroscopy are now able to provide information a million times faster than the spectroscopic methods used by him only a few years ago. Thus, he and his team have created experimental methods, analysis tools, concepts, and intuitive metaphors that will guide spectroscopy toward solutions of a wide range of practical and fundamental problems.

As the author of three books about molecular spectroscopy, awardee of the 1990 Nobel Laureate Signature Award of the American Chemical Society and various other awards and fellowships, and the author of over 380 papers, Dr. Field’s research has become a vibrant example of the value of curiosity-based research. Dr. Field has worked to extend the frontiers of spectroscopy to measurements of structural and dynamical properties that had previously been considered experimentally inaccessible, or altogether impossible. His focus on particular molecules has involved great depth as well as breadth. While he and his team have studied various types of molecules over the years, he has chosen to invest many graduate student person-years into the study into the secrets encoded in the spectra of a few special molecules. With collaborations all over the world including France, China, Germany, Belgium, Switzerland, Japan, Canada, Australia, Israel, Holland, Spain, Sweden, England, and the US, in addition to a supportive lab environment for his students at MIT, Dr. Field’s research is likely to continue to guide the field.

Current research includes:

  • Observing the Unobservable: At the center of all chemical changes, a molecular assembly must pass through a transition state. This is an essential quantity for understanding but also unobservable because of how quickly the molecule passes through it. Until recently, there was no way to observe the dance of the atoms as they transit through this special point. Dr. Field’s experiments have been helping to develop methods and models that reveal and describe this central concept of chemistry.

  • Observing Resonance: Electrons are light while nuclei are heavy, which means that it becomes exceptionally difficult for electrons to transfer energy to nuclei efficiently. When studying Rydberg states, or a state of an atom or molecule in which one of the electrons has been excited to an orbital at high principal quantum number, the electron transfers energy either through hard collisions when it comes crashing into the nucleus or through a resonance interaction where the electron’s orbit-frequency matches the frequency of an internal motion of the nuclei. This second type of energy transfer, resonance, is at the core of how energy moves around in a molecule. Using revolutionary forms of spectroscopy, Dr. Field is systematically observing these resonances in the spectra of molecular Rydberg states.

  • Studying Individual Molecules: Since the earliest moments of his academic career, Dr. Field has been studying a few special molecules in order to create unconventional global models that are accessible and understandable to the scientific community. In fact, his Ph.D. research involved creating a global model for carbon monoxide; completed in 1971, he is still asked to provide extensions of the model and new uses for the information contained in that model. Similarly, for the last thirty years, he has studied acetylene, amounting to roughly 100 MIT graduate student work years. By learning the language of molecular dynamics through the deep study of one molecule at a time, Dr. Field has transformed the discipline of molecular spectroscopy.

Bio

Dr. Robert Field was raised by a mother who was an educator and a father who was a chemist, thus instilling in him from an early age the importance of both education and the excitement accompanying the sciences. Even as a child his naturally inquisitive nature led him to question the world while his intuitive nature led him to feel passion for the issues he was questioning. For instance, as a child, Dr. Field was fascinated by record players; with a love of music in addition to wanting to understand how things worked, watching a record player produce sound was a beloved pastime. So beloved that when his mom once commented that he had “broken a record” (due to a growth spurt he had that year), he misunderstood and began to cry believing he had indeed broken a musical record. While his first record, growing as young boys do, may have been of little consequence, Dr. Field has since continued to “break records” that have inspired the scientific community.

Dr. Field’s first academic encounters with science in elementary school were met with resistance due to the unwillingness of his teacher to listen to his excited response to a film strip about tile roofs in Holland. However, after transferring to the University of Chicago Laboratory School in the sixth grade, the magical world of science was revealed to him fully. It was at the Lab School where Dr. Field was encouraged by teachers like Mr. Tenenberg, who Dr. Field still remembers fondly as a man who “was genuinely curious about what each of his students thought and felt about everything.” With supportive guidance, Dr. Field continued to engage in the sciences with vigor, which in high school even led to summer employment in chemistry labs where he cleaned glassware, measured the capacity of ion-exchange resins, and had his first tastes of spectroscopy and the career-defining challenge to build an original scientific model to explain his spectra.

Thus, as Dr. Field entered his Freshman year at Amherst college, he knew that he wanted to supplement the passions that had been fostered for the sciences, and especially chemistry with a strong academic backing. A major turning point was when he approached his advisor and asked him what kind of spectrum would be observable. His advisor proceeded to perform what Dr. Field refers to as a “mysterious calculation” on a scrap piece of paper. That “mysterious calculation” turned out to be an elementary application of Group Theory and made Dr. Field feel as if he had to learn how to do what his advisor had done, to construct elegantly simple models that explained phenomena that could not be understood with the naked eye.

Dr. Field eventually became a Physical Chemist because he was fascinated by how a spectrum, which is a richly mysterious set of transition frequencies and relative intensities, encodes the geometric structure and the intramolecular gymnastics of a molecule, a molecule rearranging its bonds, and the mechanisms for the seemingly impossible transfer of energy between a light electron and a heavy nucleus. It has been his lifelong adventure discovering how geometric structure is extracted from spectral patterns and dynamics is revealed by broken patterns. He and his students have ventured deeply into experimentally obtained pictures of processes that textbooks specify as experimentally unviewable.

In his free time, aside from research, Dr. Field enjoys watching movies, and especially enjoys French movies, which he feels share the texture of characters rather than just plot. Some of his favorite non-French movies of late include Chinatown, Oh Brother Where Art Thou, Fargo, Moonrise Kingdom, and The Grand Budapest Hotel. Consistent with his love of French movies, Dr. Field also has a love for all things French. With collaborators in France, he has often made the journey abroad where he enjoys getting to know a new culture and the people that reside within it. Upon reflection however, Dr. Field insists that his main hobby is the science. As he doesn’t have children of his own, his students have become his adopted children and his lab, a home for both him and those he mentors.

Website: http://chemistry.mit.edu/people/field-robert

Publications

Rydberg Chirped-Pulse Millimeter-Wave Spectroscopy of Rydberg-Rydberg Transitions

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Design and evaluation of a pulsed-jet chirped-pulse millimeter wave spectrometer for the 70-102 GHz region

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A New Approach Toward Transition State Spectroscopy

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Observation of the simplest Criegee intermediate CH2 OO in the gas-phase ozonolysis of ethylene” Science Advances

Accepted 2/8/2015

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Millimeter-wave optical double resonance schemes for rapid assignment of perturbed spectra, with applications to the C 1B2 state

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Intramolecular Dynamics: Representations, Visualizations, and Mechanisms

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Awards

H. P. Broida Prize in Atomic and Molecular Spectroscopy, 1980

Chemical Physics, American Physical Society, 1980

Arthur L. Schawlow Prize in Laser Science, American Physical Society, 2009

E. Bright Wilson Award, American Chemical Society, 2012

Fellow American Academy of Arts and Sciences, 1998

Member National Academy of Sciences of the United States of America, 2013