A fundamental question in nuclear physics is what combinations of neutrons and protons can make up a nucleus. Many hundreds of exotic neutron-rich isotopes have never been observed; the limit of how many neutrons a given number of protons can bind is unknown for all but the lightest elements, owing to the delicate interplay between single particle and collective quantum effects in the nucleus. This limit, known as the neutron drip line, provides a benchmark for models of the atomic nucleus. Here we report a significant advance in the determination of this limit: the discovery of two new neutron-rich isotopes--40Mg and 42Al--that are predicted to be drip-line nuclei. In the past, several attempts to observe 40Mg were unsuccessful; moreover, the observation of 42Al provides an experimental indication that the neutron drip line may be located further towards heavier isotopes in this mass region than is currently believed. In stable nuclei, attractive pairing forces enhance the stability of isotopes with even numbers of protons and neutrons. In contrast, the present work shows that nuclei at the drip line gain stability from an unpaired proton, which narrows the shell gaps and provides the opportunity to bind many more neutrons.
The excitation function for production of 262 Bh in the odd-Z-projectile reaction 208 Pb( 55 Mn, n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from 262 Bh and 2 decay chains originating from 261 Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540 +180 −150 pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than five times larger than that expected based on previously reported results for production of 262 Bh in the analogous even-Z-projectile reaction 209 Bi( 54 Cr, n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the optimum energy rule proposed byŚwia˛tecki, Siwek-Wilczyńska, and Wilczyński.
This is the first report on metallic species transfer from aqueous hydrochloric and oxalic acid media into hydrophobic deep eutectic and low-transition-temperature mixtures composed of quaternary ammonium salts or menthol and carboxylic acids.
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