atomic spectra

(noun)

emission or absorption lines formed when an electron makes a transition from one energy level of an atom to another

Related Terms

  • α-particle
  • nucleus

Examples of atomic spectra in the following topics:

  • Hydrogen Spectra

    • For decades, many questions had been asked about atomic characteristics.
    • From their sizes to their spectra, much was known about atoms, but little had been explained in terms of the laws of physics.
    • (It was a running joke that any theory of atomic and molecular spectra could be destroyed by throwing a book of data at it, so complex were the spectra.)
    • In some cases, it had been possible to devise formulas that described the emission spectra.
    • As you might expect, the simplest atom—hydrogen, with its single electron—has a relatively simple spectrum.
  • Nuclear Size and Density

    • It can be measured by the scattering of electrons by the nucleus and also inferred from the effects of finite nuclear size on electron energy levels as measured in atomic spectra.
    • The problem of defining a radius for the atomic nucleus is similar to the problem of atomic radius, in that neither atoms nor their nuclei have definite boundaries.
    • Nuclear density is the density of the nucleus of an atom, averaging about $4 \cdot 10^{17} \text{kg/}\text{m}^3$.
    • Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.Bottom: Observed results: a small portion of the particles were deflected, indicating a small, concentrated positive charge.
  • Energy of a Bohr Orbit

    • To be more general, we note that this analysis is valid for any single-electron atom.
    • So, if a nucleus has $Z$ protons ($Z=1$ for hydrogen, $Z=2$ for helium, etc.) and only one electron, that atom is called a hydrogen-like atom.
    • The spectra of hydrogen-like ions are similar to hydrogen, but shifted to higher energy by the greater attractive force between the electron and nucleus.
    • This is consistent with the planetary model of the atom.
    • The energy of the $n$-th level for any atom is determined by the radius and quantum number:
  • The Bohr Model of the Atom

    • In 1913, after returning to Copenhagen, he began publishing his theory of the simplest atom, hydrogen, based on the planetary model of the atom.
    • From their sizes to their spectra, much was known about atoms, but little had been explained in terms of the laws of physics.
    • This atom model is disastrous, because it predicts that all atoms are unstable.
    • Therefore, his atomic model is called a semiclassical model.
    • Niels Bohr, Danish physicist, used the planetary model of the atom to explain the atomic spectrum and size of the hydrogen atom.
  • X-Ray Spectra: Origins, Diffraction by Crystals, and Importance

    • X-ray shows its wave nature when radiated upon atomic/molecular structures and can be used to study them.
    • However, since atoms and atomic structures have a typical size on the order of 0.1 nm, x-ray shows its wave nature with them.
    • When x-ray are incident on an atom, they make the electronic cloud move as an electromagnetic wave.
    • This is called Rayleigh Scattering, which you should remember from a previous atom.
    • Not only do x-rays confirm the size and shape of atoms, they also give information on the atomic arrangements in materials.
  • Beta Decay

    • Beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted from an atomic nucleus.
    • Beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted from an atomic nucleus, as shown in .
    • Beta decay is a process that allows the atom to obtain the optimal ratio of protons and neutrons.
    • The continuous energy spectra of beta particles occur because Q is shared between a beta particle and a neutrino.
    • β decay in an atomic nucleus (the accompanying antineutrino is omitted).
  • Matter and Antimatter

    • For example, a positron (the antiparticle of the electron, with symbol e+) and an antiproton (symbol p-) can form an antihydrogen atom .
    • Antimatter galaxies, if they exist, are expected to have the same chemistry and absorption and emission spectra as normal-matter galaxies, and their astronomical objects would be observationally identical, making them difficult to distinguish from normal-matter galaxies.
  • X-Rays

    • When the electrons hit the target, x-rays are created through two different atomic processes:
    • X-ray fluorescence, if the electron has enough energy that it can knock an orbital electron out of the inner electron shell of a metal atom.
    • Its unique features are x-ray outputs many orders of magnitude greater than those of x-ray tubes, wide x-ray spectra, excellent collimation, and linear polarization.
  • The Michelson Interferometer

    • As shown in previous atoms, when two waves with the same frequency combine, the resulting pattern is determined by the phase difference between the two.
    • It has played an important role in studies of the upper atmosphere, revealing temperatures and winds (employing both space-borne and ground-based instruments) by measuring the Doppler widths and shifts in the spectra of airglow and aurora.
  • Spectra

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