Quantum tunneling is a strange phenomenon where tiny particles manage to pass through barriers they technically don\u2019t have the energy to overcome.\u00a0<\/p>\n
It\u2019s like a person walking toward a locked door, and instead of opening it, they suddenly appear on the other side without breaking it or going around.<\/p>\n
Until now, this phenomenon<\/a> had mostly been observed in the smallest particles, like electrons, lightweight atoms such as hydrogen, and, occasionally, oxygen and nitrogen. However, for the first time, a new study shows that under the right conditions, fluorine, too, can tunnel<\/a>.\u00a0<\/p>\n This new finding doesn\u2019t just break the so-called fluoro wall, a long-held belief that heavy atoms like fluorine aren\u2019t supposed to tunnel, but could also reshape how we understand chemical reactions and develop materials and medicines involving fluorine.<\/p>\n How to make a fluorine atom tunnel?<\/p>\n The authors began their research over a decade ago while studying how fluorine behaves when bonded to transition metals. Using a laser, they blasted metal and fluorine atoms together and then trapped the resulting compounds in a matrix of frozen neon gas<\/a> cooled to \u2013270\u00b0C.\u00a0<\/p>\n This allowed them to freeze molecules in place and study them using infrared (IR) spectroscopy, a technique that reveals details about a molecule\u2019s structure and motion. However, something strange kept showing up.\u00a0<\/p>\n One of the IR signals they detected didn\u2019t match any known metal fluoride compound. In fact, it seemed to have no metal at all. After a lot of head-scratching and years of experiments, they realized they were looking at an unusual molecule made of just fluorine<\/a> atoms\u2014specifically, a negatively charged ion with five fluorine atoms, called F\u2085\u207b.\u00a0<\/p>\n Normally, fluorine atoms are so electronegative and reactive that squeezing five of them into a single ion should make it fall apart, but this one was mysteriously stable inside the neon matrix.<\/p>\n That was only the beginning. The team noticed something else peculiar: the IR signal of this F\u2085\u207b ion was split, as if the molecule was switching between two forms.\u00a0<\/p>\n To figure out why,\u00a0 the study authors ran detailed quantum mechanical simulations. These simulations suggested that the central fluorine atom wasn\u2019t staying in one place. It was actually tunneling back and forth between two equivalent positions in the molecule. In classical physics, that would require the atom to overcome an energy barrier, which fluorine simply shouldn\u2019t be able to do due to its mass.\u00a0<\/p>\n However, the tunneling effect allowed it to bypass the barrier altogether. This behavior had only ever been observed in lighter atoms. Fluorine was thought to be too heavy, but the experiments and simulations agreed perfectly, proving that quantum tunneling for fluorine is not only possible but observable under the right conditions.<\/p>\n This could change quantum chemistry<\/p>\n This discovery opens up a new chapter in quantum chemistry. It shows that tunneling isn\u2019t just a trick for lightweight atoms; it might be more common than we thought, especially when molecules are in tightly packed, high-energy environments like the F\u2085\u207b ion.\u00a0<\/p>\n This could help scientists better understand how certain fluorinated compounds behave, something that\u2019s important in everything from drug development to battery technology<\/a>. For example, fluorinated groups are used in medicines to help them absorb better in the body, and in batteries to improve efficiency.<\/p>\n