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The Atomic Spectra Database (ASD) contains data for radiative transitions and energy levels in atoms and atomic ions. Data are included for observed transitions and energy levels of most of the known chemical elements. ASD contains data on spectral lines with wavelengths from about 0.2 Å (ångströms) to 60 m (meters). For many lines, ASD includes radiative transition probabilities. The energy level data include the ground states and ionization energies for all spectra. Except where noted, the data have been critically evaluated by NIST. For most spectra, wavelengths, transition probabilities, relative intensities, and energy levels are integrated, so that all the available information for a given transition is incorporated under a single listing. For classified lines, in addition to the observed wavelength, ASD includes the Ritz wavelength, which is the wavelength derived from the energy levels. The Ritz wavelengths are usually more precise than the observed ones. Line lists containing classified lines can be ordered by either multiplet (for a given spectrum) or wavelength. For some spectra, ASD includes lists of prominent lines with wavelengths and relative intensities but without energy-level classifications.
The Square Kilometre Array (SKA) is a radio telescope with around one million square metres of collecting area, designed to study the Universe with unprecedented speed and sensitivity. The SKA is not a single telescope, but a collection of various types of antennas, called an array, to be spread over long distances. The SKA will be used to answer fundamental questions of science and about the laws of nature, such as: how did the Universe, and the stars and galaxies contained in it, form and evolve? Was Einstein’s theory of relativity correct? What is the nature of ‘dark matter’ and ‘dark energy’? What is the origin of cosmic magnetism? Is there life somewhere else in the Universe?