The Unprecedented Stability of Tantalum-180m Isotope and Its Implications

Tantalum is known to be one of the rarest elements, with multiple stable isotopes. Among these isotopes, Ta-180 stands out as the least abundant and possesses a long-lived excited state, which is an exceptional feature unique to this particular isotope. In excited states, the protons or neutrons within a nuclei exhibit higher energy levels than normal, leading to a state of instability.

Despite being energetically possible, the radioactive decay of the excited state in Ta-180m has never been observed. This presents a significant challenge for researchers who are now conducting experiments to measure this decay. The expected lifetime of this decay is approximately 1 million times longer than the age of the universe, making it an unprecedented scientific endeavor.

The decay of excited states of nuclei, such as Ta-180m, offers valuable insights into how nuclei deform in such states. While nuclear physicists have extensively studied the variations in shape and the formation of short-lived isotopes known as isomers, the decay of Ta-180m remains largely unexplored. By predicting the decay of Ta-180m using nuclear theory, researchers aim to challenge existing models and theories of nuclear structure and decay.

Scientists have recently devised an experiment to measure the decay of Ta-180m with unprecedented sensitivity. By restructuring the MAJORANA ultra-low background facility at the Sanford Underground Research Facility in South Dakota and introducing a larger tantalum sample, researchers have been able to collect data using germanium detectors with exceptional energy resolution. This experimental setup has led to the establishment of the longest limits ever achieved in nuclear isomer studies, falling within the range of 10^18 to 10^19 years.

While the decay process of Ta-180m has not been observed yet, the advancements made in this research have significantly enhanced the existing limits by one to two orders of magnitude. This progress not only contributes to our understanding of nuclear structure and decay but also allows researchers to dismiss certain parameter ranges associated with potential dark matter particles. Moving forward, further experiments and analyses are needed to fully unravel the mysteries surrounding the stability of Ta-180m and its implications for nuclear theory.