LANS Seminar

Seminar Title: Isospectrality in rotational spectroscopy: does a rotational spectrum uniquely identify a molecule?

Speaker: Marcus Schwarting, PhD Candidate, Computer Science, University of Chicago

Date/Time: March 20, 2024/ 10:30 AM-1:30 AM
Location: See Meeting URL on the cels-seminars website which will require an Argonne login.

Description: For any spectroscopic technique, the isospectrality problem of determining whether a captured spectrum uniquely defines a molecule is critically important.  Rotational spectroscopy provides unique conformational and structural insights. It has long been considered that a rotational spectrum, when assigned, represents a unique “fingerprint” of a molecule. With the proliferation of broadband rotational spectroscopy, availability of large molecular databases, and development of AI methods for rotational spectroscopy, the question of isospectrality can now be revisited. Recent attempts of solving the inverse problem – determining a molecule’s geometry from a set of rotational constants or the rotational spectrum itself – leads to the question of solution uniqueness. Our constructive approaches study the distribution of moments of inertia in a constrained and unconstrained environment, and the ease with which isospectral examples can be identified or derived. Our exhaustive approaches use a funnel-based technique for identifying possible isospectral examples from large datasets of molecular geometries including QM9, QM7x, GEOM, and a subset of PubChem. We present examples where calculated rotational constants of chemically distinct molecules are identical to within the uncertainty of those calculations.

Bio: Marcus Schwarting is a PhD candidate in computer science at the University of Chicago, where his research focuses on applying deep learning to important challenges in computational chemistry, materials science, and spectroscopy. Marcus graduated from the University of Louisville in 2018 with degrees in mathematics and chemical engineering. After working for four years at the National Renewable Energy Laboratory and Argonne National Laboratory, Marcus began his PhD studies in 2020 under Dr. Ian Foster.