In a laboratory experiment that mimics astrophysical conditions, with cryogenic temperatures in an ultrahigh vacuum, scientists used an electron gun to irradiate thin sheets of ice covered in basic molecules of methane, ammonia and carbon dioxide. These simple molecules are ingredients for the building blocks of life. The experiment tested how the combination of electrons and basic matter leads to more complex biomolecule forms — and perhaps eventually to life forms.
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The internal structure of the thorium-229m nuclear state has been studied in detail for the first time by physicists in Germany. Thorium-229m is a metastable (or isomer) excited state of thorium-229 that decays via the emission of an ultraviolet (UV) photon. This photon has much lower energy than most nuclear emissions and could form the basis of a “nuclear clock” that would be much more precise than existing atomic clocks.
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After spending three months trying to blow up a star, Hans-Thomas Janka and his team finally saw what they had been waiting for. Like the world’s most patient pyromaniacs, they watched their massive stellar simulation — rendered in painstaking detail — inch closer to detonation. Each day, theirsupercomputer ticked through just 5 milliseconds of the star’s life.
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We link the structure of nuclei around 100Sn, the heaviest doubly magic nucleus with equal neutron and proton numbers (N=Z=50), to nucleon-nucleon (NN) and three-nucleon (NNN) forces constrained by data of few-nucleon systems. Our results indicate that 100Sn is doubly magic, and we predict its quadrupole collectivity. We present precise computations of 101Sn based on three-particle–two-hole excitations of 100Sn, and we find that one interaction accurately reproduces the small splitting between the lowest Jπ=7/2+ and 5/2+ states.
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With the end of the Cold War, most physicists turned their attention away from the nuclear threat. It is now time for us to reengage in the debate over how to reduce the dangers from nuclear weapons.
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It is shown that superheavy elements may also be formed in the main r process responsible for the formation of the heaviest elements observed in nature. Under conditions of a high neutron density, the nucleosynthesis region lies close to the neutron drip line, so that the r process may circumvent the region where nuclei undergo spontaneous fissions and therefore have short lifetimes. However, a high induced-fission rate, which increases with the charge number, may prevent the nucleosynthesis wave from overcoming the region of isotopes heavier than curium, and the beta-decay chain leading to an increase in the charge number of product elements inevitably results in the spontaneous fission of the majority of product nuclei. Calculations of nucleosynthesis that were performed with available nuclear data within the scenario of a neutron-star merger reveal that only Z < 106 superheavy elements are formed. Their abundance at the end of the r process is commensurate with the abundance of uranium, but their lifetime does not exceed several years, so that they fast undergo decay.
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Nuclear fusion is regularly created in spherical plasma compressions driven by multi-kilojoule pulses from the world’s largest lasers. Here we demonstrate a dense fusion environment created by irradiating arrays of deuterated nanostructures with joule-level pulses from a compact ultrafast laser. The irradiation of ordered deuterated polyethylene nanowires arrays with femtosecond pulses of relativistic intensity creates ultra-high energy density plasmas in which deuterons (D) are accelerated up to MeV energies, efficiently driving D–D fusion reactions and ultrafast neutron bursts. We measure up to 2 × 106 fusion neutrons per joule, an increase of about 500 times with respect to flat solid targets, a record yield for joule-level lasers. Moreover, in accordance with simulation predictions, we observe a rapid increase in neutron yield with laser pulse energy. The results will impact nuclear science and high energy density research and can lead to bright ultrafast quasi-monoenergetic neutron point sources for imaging and materials studies.
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