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Commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6.8 GHz (6 834 682 610.904 Hz). The intensity of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1% when the rubidium vapor in the resonance cell is exposed ...
Other than 87 Rb, the longest-lived radioisotopes are 83 Rb with a half-life of 86.2 days, 84 Rb with a half-life of 33.1 days, and 86 Rb with a half-life of 18.642 days. All other radioisotopes have half-lives less than a day. 82 Rb is used in some cardiac positron emission tomography scans to assess myocardial perfusion. It has a half-life of ...
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear.
The main decay mode for isotopes heavier than 244 Pu, along with 241 Pu and 243 Pu, is beta emission, forming americium isotopes (95 protons). Plutonium-241 is the parent isotope of the neptunium series, decaying to americium-241 via beta emission. [11] [26] Plutonium-238 and 239 are the most widely synthesized isotopes.
Thorium nuclei are susceptible to alpha decay because the strong nuclear force cannot overcome the electromagnetic repulsion between their protons. [21] The alpha decay of 232 Th initiates the 4n decay chain which includes isotopes with a mass number divisible by 4 (hence the name; it is also called the thorium series after its progenitor).
Dubnium is a synthetic chemical element; it has symbol Db and atomic number 105. It is highly radioactive: the most stable known isotope, dubnium-268, has a half-life of about 16 hours.
Xenon has atomic number 54; that is, its nucleus contains 54 protons. At standard temperature and pressure , pure xenon gas has a density of 5.894 kg/m 3 , about 4.5 times the density of the Earth's atmosphere at sea level, 1.217 kg/m 3 . [ 52 ]
Protons were measured in the following energy ranges: 0 to 5, 0 to 20, 0 to 80, 0 to 250, 0 to 800, and 0 to 2300 eV. The experiment was mounted on the spacecraft so that the symmetry axis of the plasma probe was perpendicular to the spacecraft spin axis. The Faraday cup had its maximum response to particles incident at 0° to its symmeter axis ...