Fine Structure


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Related to Fine Structure: hyperfine structure

Fine structure (spectral lines)

The closely spaced groups of lines observed in the spectra of the lightest elements, notably hydrogen and helium. The components of any one such group are characterized by identical values of the principal quantum number n, but different values of the azimuthal quantum number l and the angular momentum quantum number j.

In atoms having several electrons, this fine structure becomes the multiplet structure resulting from spin-orbit coupling. This gives splittings of the terms and the spectral lines that are “fine’’ for the lightest elements but that are very large, of the order of an electronvolt, for the heavy elements.

Fine Structure

 

(or multiplet splitting), a splitting of the energy levels and spectral lines of atoms, molecules, and crystals that is caused by spin-orbit coupling. The number of sublevels into which an energy level is split depends on the number of possible spin orientations—that is, on the multiplicity K—and does not exceed K. In particular, for alkali-metal atoms the spin of the outer electron can have two orientations (K = 2); in this case, the energy levels are split into two sublevéis (doublet splitting), and the spectral lines are split into two closely spaced levels (doublets). For light atoms the magnitude of the fine-structure splitting of energy levels does not exceed 10–4 electron volt; for spectral lines the corresponding magnitude is several wave number units (cm–1). The splitting increases markedly as the nuclear charge Z becomes larger. The splitting of the energy levels of heavy atoms may reach several tenths of an electron volt.

M. A. EL’IASHEVICH

fine structure

[¦fīn ′strək·chər]
(atomic physics)
The splitting of spectral lines in atomic and molecular spectra caused by the spin angular momentum of the electrons and the coupling of the spin to the orbital angular momentum.
References in periodicals archive ?
Lytle, "Extended x-ray absorption fine structure determination of thermal disorder in Cu: comparison of theory and experiment," Physical Review B, vol.
Braekevelt, "Fine structure of the pecten oculi of the mallard (Anas platyrhynchos)," Canadian Journal of Zoology, vol.
The other had the same spectrum of [alpha]-carotene and presented more defined spectral fine structure compared to that of [beta]-carotene; it may be identified as zeinoxanthin or [alpha]-cryptoxanthin.
The present paper describes the fine structure of hagfish spermiogenesis in detail, using the Japanese hagfish Eptatretus burgeri.
where [m.sub.p] is the proton mass, [alpha] is the fine structure constant, [e.sub.V.sup.R] is a low energy constant, [[partial derivative].sub.a]'s are model-independent radiative corrections, [[~.g].sub.A] is the axial coupling constant, and the correlation coefficients a, A, B are incorporated into the recoil corrections [C.sub.i]([E.sub.e]) [6].
Based on these outstanding features, the present study focuses on the fine structure of the spermatozoa, which are briefly compared with our own unpublished observations on other theridiid spiders.
Finally, in a return to the original cell wall theme, the fine structure of mannans and galactomannans is explained as a useful adjunct in classifying fungi.
The purpose of this paper is to describe the fine structure of the "window", bristles and scales of the wings of R.
Strong capabilities have been built in capillary and nanoscale LC separations and in the use of MS for the identification and fine structure characterization of protein samples digested by enzymes.
(1998) studied the fine structure of the tongue of penguin which presented the dorsal surface densely distributed with large spine-like lingual papillae.