In a significant advance for nuclear physics, scientists have demonstrated a novel technique to study the internal properties of an atomic nucleus from a tabletop apparatus. Researchers at the Massachusetts Institute of Technology (MIT) used a specially crafted molecule to turn an atom’s own electrons into precise probes, sending them into the nucleus to report back on its structure. This method provides a more accessible alternative to the massive particle accelerators traditionally required for such investigations and could accelerate the search for answers to some of cosmology’s most profound questions.
The experiment, detailed in the journal Science, centers on using radium monofluoride molecules to scrutinize the nucleus of the radium atom. By measuring subtle energy shifts in electrons that have briefly penetrated the nucleus, the team can map the distribution of its internal components. This approach not only offers a new way to measure nuclear properties but also holds the potential to reveal violations of fundamental physical symmetries, which could help explain why the universe is composed almost entirely of matter and not its counterpart, antimatter.
A Molecule-Sized Particle Collider
Traditional methods for probing the atomic nucleus involve enormous, often kilometers-long facilities that smash beams of electrons into atoms at tremendous speeds. The new technique developed by the MIT team effectively creates a particle collider within the confines of a single molecule. This innovative, non-destructive approach can be performed in a comparatively small laboratory setting.
The researchers, including Ronald Fernando Garcia Ruiz, Shane Wilkins, and Silviu-Marian Udrescu, along with collaborators at CERN, chose the radium monofluoride (RaF) molecule for its unique properties. Radium is a heavy, radioactive element with a nucleus that is predicted to be pear-shaped rather than spherical, making it an ideal candidate for studying fundamental symmetries. When a radium atom is paired with a fluoride atom, it creates an extremely powerful internal electric field—stronger than anything that can be generated externally in a lab. This field effectively compresses the electron cloud around the radium atom, greatly increasing the chances that an electron will venture inside the nucleus itself.
Reading Nuclear Messages from Within
The core of the experiment relies on using electrons as internal messengers. Once an electron penetrates the crowded confines of the radium nucleus, it interacts with the protons and neutrons inside before emerging. This fleeting interaction imparts a tiny, yet measurable, change to the electron’s energy level. This “energy shift” serves as a fingerprint, carrying information about the nuclear interior.
Precision Laser Spectroscopy
To read these subtle messages, the science team first trapped and cooled the radium monofluoride molecules. They then directed the molecules through a system of vacuum chambers, where they were exposed to precisely tuned lasers. This laser spectroscopy allowed the physicists to measure the energy levels of the electrons within each molecule with extraordinary accuracy. By detecting the slight energy shifts, they could confirm that electrons had indeed entered the nucleus and returned with valuable data about its structure.
Mapping the Nuclear Landscape
This technique provides a direct path to mapping the nuclear magnetic distribution of the radium nucleus for the first time. Inside a nucleus, each proton and neutron behaves like a subatomic magnet, and their collective arrangement determines the overall magnetic character of the nucleus. Understanding this distribution offers deep insights into the forces and structures that hold the nucleus together.
The unusual pear shape of the radium nucleus makes these measurements particularly compelling. This asymmetry is thought to be a key area for investigating violations of fundamental symmetries in physics. The ability to map the forces and charge distribution within such a nucleus provides a powerful new tool in this search.
Probing a Grand Cosmological Mystery
One of the most significant applications for this new method is its potential to shed light on the universe’s matter-antimatter imbalance. The Standard Model of particle physics predicts that the Big Bang should have produced matter and antimatter in equal quantities. However, the observable universe is overwhelmingly made of matter. This discrepancy suggests that there are undiscovered processes that violate the expected symmetries between matter and its counterpart.
By precisely measuring the properties of the radium nucleus, the researchers hope to find evidence of this symmetry-breaking. The particular arrangement of protons and neutrons in its pear-shaped nucleus could reveal subtle effects that favor matter over antimatter, providing a crucial clue to solving this long-standing puzzle. The results from this tabletop experiment lay the groundwork for a new generation of studies aimed at exploring the fundamental laws of nature at the nuclear level.
