Spectra Spectral lines

Emission spectroscopy provides an ideal method for qualitative analysis, since each atomic species has its own unique line spectrum. Spectral lines have two characteristics useful for qualitative analysis (1) their wavelengths and (2) their intensities. It is the pattern of wavelength distribution that is primarily used for qualitative analysis, although the relative intensity distribution also can be helpful to verify spectral lines to identify an element. About 70 elements are easily identified by spectral methods. Those that are more difficult to identify include the gases and a few nonmetals, primarily because sensitive lines lie in the short ultraviolet portion of the spectrum that is difficult to observe. 

As discussed above, the spectrum must be assigned, i.e. the quantum numbers of the upper and lower levels of the spectral lines must be available. In addition to the line positions, intensity infomiation is also required. 

Spektralanalyse, /. spectrum analysis, spektralanalytisch, a. spectroscopic, spectro-metric. — adv. by spectrum analysis. Spektral-apparat, to. spectroscopic apparatus, -beobachtung, /. spectroscopic observation, -bereich, -bezirk, to. spectral region, -farbe, /. spectral color, spectrum color, -gegend, /. spectral region, -lampe, /. spectrum lamp, -hnie, /. spectrum line, spectral line, -probe, /. spectrum test, -rohr, n.. -rohre, /. spectrum tube, spectral tube, -tafel, /. spectrum chart, spectral chart. 

Because these photons are produced when an electron moves from one energy level to another, the electronic energy levels in an atom must be quantized, that is, limited to particular values. Moreover, it would seem that by measuring the spectrum of an element it should be possible to unravel its electronic energy levels. This is indeed possible, but it isn t easy. Gaseous atoms typically give off hundreds, even thousands, of spectral lines. 

FIGURE 1.10 (a) The visible spectrum, (b) The complete spectrum of atomic hydrogen. The spectral lines have been assigned to various groups called series, two of which are shown with their names. 

The existence of photons and the relation between their energy and frequency helps to answer one of the questions posed by the spectrum of atomic hydrogen. At the end of Section 1.3 we started to form the view that a spectral line arises from a transition between two energy levels. Now we can see that if the energy difference is carried away as a photon, then the frequency of an individual line in a spectrum is related to the energy difference between two energy levels involved in the transition (Fig. 1.18) ... 

The Humphreys series is set of spectral lines in the emission spectrum of atomic hydrogen that ends in the fifth excited state. 

In the spectrum of atomic hydrogen, a violet line is observed at 434 nni. Determine the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line. 

Balmer series A family of spectral lines (some of which lie in the visible region) in the spectrum of atomic hydrogen. 

The discovery of two other series of emission lines of hydrogen came later. They are named for their discoverers the Lyman series in the ultraviolet range and Paschen series in the infrared region. Although formulas were devised to calculate the spectral lines, the physics behind the math was not understood until Niels Bohr proposed his quantized atom. Suddenly, the emission spectrum of hydrogen made sense. Each line represented the energy released when an excited electron went from a higher quantum state to a lower one. 

The spectrum of hydrogen (Z = 1) is divided into a number of series of spectral lines, each series having a particular value for n. As many as six different series have been observed ... 

This splitting of the energy levels by the magnetic field leads to the splitting of the lines in the atomic spectrum. The wave number v of the spectral line corresponding to a transition between the state /i mi) and the state nihm2) is... 

The spectrum of atomic hydrogen, as observed in absorption or emission, arises from transitions between tile various possible states. In emission, a spectral line results from a transition such as n2 i and the application of Eq. (84) leads to the expression... 

The very high resolution for the ESR spectrum of cob(II)alamin in the enzyme system is undoubtedly due to the fact that all the coenzyme molecules are bound in an identical environment at the enzyme active site. This results in a homogeneous cobalt-benzimidazole geometry, because both identical binding sites, solvent, and solute molecules can no longer approach the Bia-molecule closely. In addition, the enzyme bound cob(II)alamin molecules are more isolated from one another and thus relaxation due to spin-spin interactions is less effective in broadening spectral lines. 

ESR spectral lines in a frozen solution or powder spectrum are sometimes peculiarly broad. The phenomenon is sometimes called g-strain . In most cases, the matter is dropped at that point and no attempt to explain further is made. A successful interpretation of the effect has, however, been made for some organometallic radicals.48... 

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