A guide to events on our campuses.

Assembly Series

A tradition of convening thought leaders since 1953

McKelvey School of Engineering

Can You Believe It – Even More Fun with God’s Quantum Dots!

Thursday, May 5 | 4:00 PM

William Louderman Hall, 458
Louderman Hall, St. Louis, MO 63105

L. G. Sobotka - Departments of Chemistry and Physics, Washington University.

The second (nuclear) excited state in 12C is the gateway to the periodic table. The resonant capture of 3 alpha particles, (with 8Be as an intermediate) into this state with subsequent electromagnetic decay, is the accepted mechanism for generating 12Cgs. This nuclide then serves as the seed for the synthesis of all heavier elements. However another mechanism was proposed 55 years ago that could provide a parallel path to bound 12C.  During covid times we did an experiment that allows (via microscopic reversibility and a first-of-its-kind measurement) this alternative to be (finally) evaluated. The window of relevance for this alternate path is narrow. This work is part of a program to study resonant doorways to element making via studying inverse (decay) processes. A side product of this effort is the discovery of 6 new isotopes that are so proton rich that they immediately decay by spitting out multiple protons.  How we do these experiments and our program’s relation to the Anthropic principle will be discussed. Finally, this program also has provided a qualifier to the worn adage in quantum mechanical barrier penetration that the action (the forbidden momentum-distance area of a potential, made unit less by dividing by hbar) cannot be decomposed to inform on the shape of the barrier traversed. The adage is wrong if two particles, correlated only by energy conservation, penetrate a common barrier.

Event Type

Lectures & Presentations


Arts & Sciences



Google Calendar iCal Outlook