Dispersed emission spectrum

Fig. 14 A dispersed emission spectrum of BaO, excited to the C E" " state by double resonance via the A Ie" state (Reproduced with permission from J. Mol. Spectrosc. 1980, 82. 283)...

Fig. 4. Dispersed emission spectrum following double resonance...

Separate the light from the emission spectrum of the Sun and you will see the familiar rainbow colour spectrum but how small a wavelength difference can be detected Is it possible to tell between 500 nm and 501 nm The spectral resolution limits the ability of a telescope to tell the difference between two spectral lines and hence two different molecules. The smallest separation that allows two wavelengths to be distinguished is limited by the physics of dispersion and for sources of the same intensity, Lord Rayleigh determined that the dip between the two peaks should be 8/7r 2 or about 19 per cent. 

Zinc me.w-tetrakis (p-carboxyphenyl)porphyrin (ZnTPPC), a neutral molecule, can be readily intercalated into the Li-Al LDH-myristate interlayers by replacing the myristate ions [101b], However, the uptake of the ZnTPPC into this material was minimal. The diffraction pattern showed that, as is the case with other porphyrins, ZnTPPC intercalates with its plane perpendicular to the metal hydroxide layer. The emission spectrum (excitation at 407 nm) of the intercalated guest is similar to that of nonaggregated ZnTPPC in solution (Fig. 53), suggesting that ZnTPPC is solubilized in the LDH in a dispersed form and not as an aggre-... 

Figure 5-7. Dispersed emission spectra of aniline(N2)i clusters following excitation to several vibrational states of St. Relative energy is the shift, in wavenumbers, from the excited transition. The top spectrum (TJ excitation) shows an inset trace for an expanded scale about the 0° intense feature 10b, 0 J, and JJ emission can be observed. Note that the relaxed cluster emission from 0 J (following IVR) is broad as expected (compare with 6aJ + 55 cm -1 and 6aJ excitation).

In AFS there is no need to isolate a single wavelength in the fluorescence emission spectrum from nearby, less-intense emission wavelengths, since all lines contribute to the fluorescence signal. Therefore quite large spectral bandpasses are often employed in flame AFS, especially when a low-background flame is being used. Indeed, as seen in Chapter 2, section 14, non-dispersive, filter-based systems may sometimes be employed.7,8... 

Figure 15-33. (a) Fluorescence excitation and dispersed fluorescence spectra (DFS) of HFB in supersonic free jet. The open arrows denote the feature assigned to the tto < S0 absorption, whereas the sold arrows indicate the excitation wavelength for the dispersed emissions, (b) The expanded feature of LIF spectrum in the panel (a), (c) Two views of the optimized geometries of the lowest-energy ircr state of HFB. (Reprinted with permission from Ref. [74].)... 

Most spectroscopic measurements involve the use of an appropriate combination of source, dispersive device, and detector to analyze the absorption or emission spectrum of a sample. If only the wavelength or frequency of the radiation is measured, the resultant instrument is called a spectrometer. If the instrument provides a measure of the relative intensity associated with each wavelength, it is called a spectrophotometer, but this fine distinction is often ignored. Absorption spectra are often characterized by the transmittance Tat a given wavelength this is defined by... 

When the quasistatic contribution to the absorption coefficient, as described by eq. (1), is incorporated in the LTE model (5.) a more realistic emission spectrum of the HPS discharge results (de Groot and Woerdman, to be published). This is already evident when the quasistatic absorption spectrum is compared with the extrapolated dispersive, resonantly broadened Na D absorption profile (see Figure 3). In the far red wing (X > 650 nm) the contribution of the A Sj, - X Zg transition is much larger than the dispersive contribution in a LTE model the same holds for the emission spectrum. In the far blue wing (X< 560 nm) the contribution of the Ilg - transition likewise dominates the dispersive contribution. 

Fig. 15. Rotatory artifacts that simulate Cotton effects at an absorption band. The dependence of the rotatory artifact on absorbance of p-cresol solutions placed in series with the same poly-L-glutamic acid solution is shown. The concentration of p-cresol was adjusted to give the total absorbance of chromophore plus polypeptide background that appears with each curve. The rotator, poly-L-glutamic acid, was at concentration of 0.5% at pH 7.0 in a 10-cm cell. The rotations are those actually observed, a, in degrees. The rotatory dispersion at Am 2 coincides almost exactly with that for the polypeptide alone, so that it has been omitted from the figure. At Am 4, an interference filter, /, with maximum transmission between 280 and 285 m/i, was placed in the optical path. The absorption spectrum, in arbitrary units, is typical of p-cresol plus poly-L-glutamic acid background. The emission spectrum is represented in arbitrary units, uncorrected for detector response. (Urnes et al., 1961a.)...

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