In 1921, the German physicist Otto Hahn was quite surprised by his studies of the beta decay of uranium-X1 (as thorium-234 was then called). He received a new radioactive substance, which he gave the name uranium-Z. The atomic weight and chemical properties of the new substance coincided with the previously discovered uranium-X2 (the now familiar name of protactinium-234). But the half-life was longer. In 1935, a group of Soviet physicists led by Igor Kurchatov obtained a similar result with the isotope bromine-80. After these discoveries, it became clear that world physics was faced with something unusual.
This phenomenon is called isomerism of atomic nuclei. It manifests itself in the existence of nuclei of elements that are in an excited state, but live for a rather long time. These metastable nuclei have a much lower probability of transition to a less excited state, since they are constrained by the rules of spin and parity exclusion.
By our time, several tens of isomers have already been discovered, which can pass into the state usual for an element by means of radioactive radiation, as well as spontaneous fission or emission of a proton; internal conversion is also possible.
Among all isomers, 178m2Hf aroused the greatest interest.
This hafnium isomer has a half-life of just over 31 years, and the energy latent in its transition to a normal state exceeds 300 kg in TNT equivalent per kilogram of mass. That is, if it is possible to quickly transfer 1 kg of the mass of isomeric hafnium, then it will burn like 3 centners of TNT. And this already promises a decent military use. The bomb will turn out to be very powerful, and it cannot be called nuclear - after all, there is no nuclear fission, just the element changes its isomeric structure to normal.
And the research began …
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In 1998, Karl Collins and colleagues at the University of Texas embarked on systematic research. They irradiated a piece of the aforementioned hafnium isomer resting on an inverted glass with X-rays with specified parameters. The isomer was irradiated for several days, and sensitive sensors recorded its response to radiation. Then the analysis of the obtained results began.
Dr. Karl Collins in his laboratory at the University of Texas.
Some time later, an article by Collins appeared in Physical Review Letters, in which he talked about an experiment to "extract" the energy of an isomeric transition under the influence of X-rays with given parameters. It seemed that an increase in the gamma radiation of the isomer was obtained, which indicated an acceleration of the transition of the isomer to the normal unexcited state.
Hafnium bomb
Often, what is just a mind game for physicists, for the military is a new way to destroy their own kind. Not only could it be possible to get powerful explosives (a kilogram of 178m2Hf is equivalent to three centners of TNT), but most of the energy had to be released as gamma radiation, which theoretically made it possible to disable the radio electronics of a potential enemy.
Experiment to obtain induced gamma radiation from a sample of Hf-178-m2.
The legal aspects of using a hafnium bomb also looked very tempting: when bombs explode on nuclear isomers, there is no transformation of one chemical element into another. Accordingly, the isomer cannot be considered a nuclear weapon and, as a consequence, according to the international agreement, it does not fall under the ban.
The Pentagon allocated tens of millions of dollars for experiments, and work on the hafnium bomb began to boil. A piece of 178m2Hf was irradiated in several military laboratories, but there was no result. Collins convinced the experimenters that the power of their radiation was insufficient to obtain a result, and the power was constantly increased. It got to the point that they tried to irradiate the isomer using the synchrotron of Brookhaven National Laboratory. As a result, the energy of the initial irradiation was increased hundreds of times, but there was still no tangible effect.
The senselessness of the work became clear even to the military - after all, even if the effect appears, you cannot place a synchrotron in advance on the territory of a potential enemy. And then economists took the floor. They calculated that the production of 1 gram of the isomer would cost $ 1.2 million. Moreover, to prepare this production will have to spend a tidy sum of $ 30 billion.
Hafnium.
In 2004, funding for the project was sharply cut, and after a couple of years, it was completely curtailed. Collins agreed with his colleagues' conclusions about the impossibility of creating a bomb based on the hafnium isomer, but believes that this substance can be used to treat cancer patients.
