Halo Nuclei and Strong Force Range Limits
The effective absolute limit of the range of the strong force is represented by halo nuclei such as lithium-11 or boron-14, in which dineutrons, or other collections of neutrons, orbit at distances of about ten fermis (roughly similar to the 8 fermi radius of the nucleus of uranium-238). These nuclei are not maximally dense. Halo nuclei form at the extreme edges of the chart of the nuclides—the neutron drip line and proton drip line—and are all unstable with short half-lives, measured in milliseconds; for example, lithium-11 has a half-life of less than 8.6 milliseconds.
Halos in effect represent an excited state with nucleons in an outer quantum shell which has unfilled energy levels "below" it (both in terms of radius and energy). The halo may be made of either neutrons or protons . Nuclei which have a single neutron halo include 11Be and 19C. A two-neutron halo is exhibited by 6He, 11Li, 17B, 19B and 22C. Two-neutron halo nuclei break into three fragments, never two, and are called Borromean because of this behavior (referring to a system of three interlocked rings in which breaking any ring frees both of the others). 8He and 14Be both exhibit a four-neutron halo. Nuclei which have a proton halo include 8B and 26P. A two-proton halo is exhibited by 17Ne and 27S. Proton halos are expected to be more rare and unstable than the neutron examples, because of the repulsive electromagnetic forces of the excess proton(s).
Read more about this topic: Atomic Nucleus
Famous quotes containing the words halo, strong, force, range and/or limits:
“Most books belong to the house and street only, and in the fields their leaves feel very thin. They are bare and obvious, and have no halo nor haze about them. Nature lies far and fair behind them all. But this, as it proceeds from, so it addresses, what is deepest and most abiding in man. It belongs to the noontide of the day, the midsummer of the year, and after the snows have melted, and the waters evaporated in the spring, still its truth speaks freshly to our experience.”
—Henry David Thoreau (1817–1862)
“My curiosity to see the melancholy spectacle of the executions was so strong that I could not resist it, although I was sensible that I would suffer much from it.... I got upon a scaffold near the fatal tree so that I could clearly see all the dismal scene.... I was most terribly shocked, and thrown into a very deep melancholy.”
—James Boswell (1740–1795)
“If writers were too wise, perhaps no books would get written at all. It might be better to ask yourself “Why?” afterwards than before. Anyway, the force from somewhere in Space which commands you to write in the first place, gives you no choice. You take up the pen when you are told, and write what is commanded. There is no agony like bearing an untold story inside you.”
—Zora Neale Hurston (1891–1960)
“Narrowed-down by her early editors and anthologists, reduced to quaintness or spinsterish oddity by many of her commentators, sentimentalized, fallen-in-love with like some gnomic Garbo, still unread in the breadth and depth of her full range of work, she was, and is, a wonder to me when I try to imagine myself into that mind.”
—Adrienne Rich (b. 1929)
“Mysticism and exaggeration go together. A mystic must not fear ridicule if he is to push all the way to the limits of humility or the limits of delight.”
—Milan Kundera (b. 1929)