![]() These processes compete with each other and with collisional atomic processes in the plasma, and this competition determines the level population, which is the relative number of atoms in a particular excited state. For example, the oscillator strength is a key factor in atomic processes, such as spontaneous radiative decay, stimulated emission, and photoexcitation. The oscillator strength impacts many of the microphysics aspects of atomic spectroscopy. More specifically, this dimensionless parameter describes the probability that a certain atomic transition will absorb or emit light. The oscillator strength can be thought of as the amplitude of electronic (dipole) oscillations in an atom. The discrepancy with neon-like iron concerns one of these inputs: an atomic characteristic called the oscillator strength. Analyzing such a spectrum requires comparing it to a database of synthetic spectra, which are calculated using a host of inputs that include atomic structure and atomic processes (which determine line intensities) and plasma perturbations (which impact spectral line profiles). ![]() ![]() Spectral emission lines are often the only thing that researchers have to go on when studying a hot plasma. This result will reduce uncertainties in models of gas turbulence in galaxies, for example. Now Steffen Kühn from the Max Planck Institute for Nuclear Physics in Germany and colleagues have performed experiments and data analysis that resolve this discrepancy. However, the usefulness of the most prominent lines of “neon-like” iron has been limited by a long-standing discrepancy between measurements and theoretical predictions (see Synopsis: Resolving Discrepancies in X-Ray Astronomy). An important species in these environments is ionized iron, in particular, the highly ionized state Fe +16 (also called Fe XVII), which, like a neon atom, has ten bound electrons. Chandra and XMM-Newton-two currently orbiting x-ray telescopes-use this technique to provide critical information about a wide range of astrophysical systems, including hot gas in galaxy clusters, accretion disks around black holes, and coronal envelopes of stars. ×Ītomic x-ray line spectroscopy is a nonintrusive diagnostic method for studying hot plasmas in fusion experiments on Earth and in energetic environments of outer space. ![]() The data showed agreement with calculations performed by the same group. In the experiment, light from a synchrotron impinges on a cloud of highly ionized iron atoms, and the fluorescence emission is observed. Bernitt/Helmholtz Institute Jena Figure 1: Researchers have resolved a long-standing discrepancy surrounding iron emission lines that are important in x-ray astronomy. So there's no simple rule for learning the number of electrons an atom may gain or lose in a compound (and using electricity, for example, it's possible to remove electrons well below the valence shell), though the number of electrons in the valence shell is unique.S. " So an element has a specific valence, depending on its group (e.g., C, 4 or Xe, 0), but may have multiple values for valency, such as in $\ce$. It's not simply the column that determines the ionic charge of an element, but also other factors, such as row and with what other elements it's combined.Įpediaa states, "valence refers to the ability of an atom to be combined with another atom whereas valency refers to the maximum number of electrons that an atom can lose or gain in order to stabilize itself. ![]()
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