A Mousetrap in the Atomic Nucleus: Reading Thorium with Ejected Electrons ⚡ экспресс
For the first time, a method of conversion electron spectroscopy was demonstrated for the thorium-229 nucleus: a laser excites the isomer, and the energy is transferred to an electron, which is ejected from the material (internal conversion). This works even in samples opaque to nuclear light, such as a thin ThO₂ film, where the small band gap facilitates the process. The short isomer lifetime (~10 μs) and the ability to use spinless isotopes allow the interrogation time of nuclear clocks to be reduced by a factor of 10⁸ and their instability to be lowered by 10⁴ — as if an ultra-precise stopwatch stopped getting thrown off by trembling parts.
Inside thorium-229’s nucleus lies a hair-trigger mousetrap. When struck by a laser, it normally snaps shut, releasing a twinkle of ultraviolet light. But in many crystals, that light is smothered—like a bell wrapped in cloth—making the trap seem silent. Now, physicists bypass the light entirely: they detect the snap itself by catching the electron that gets kicked out when the trap springs. This method, internal conversion spectroscopy, reads the nuclear state even through materials that would block the light.
The payoff is speed. By crafting the crystal from a specific isotope of thorium, the trap snaps in just 10 microseconds—a hundred million times faster than waiting for the light. A nuclear clock based on this electron readout could become 10,000 times more stable, potentially losing less than a second over the age of the universe. Such a clock would test whether the speed of light is truly constant and probe the Standard Model of physics for cracks.
🎯 The energy needed to spring the mousetrap is a mere 8.4 electron volts, easily delivered by a laser—most nuclear transitions demand monstrous particle accelerators.