Emission spectrum

Emission spectroscopy Emission spectrum Emissivities Emissivity Emkal... 

In the near-UV, visible and near-IR regions of the spectrum, emission is due to electronic transitions in excited atoms and molecules, while in the near- and mid-IR it is due to vibrational transitions within molecules. 

Figure 23-13 (A) Corrected emission and excitation spectra of riboflavin tetrabutyrate in w-heptane. Concentration, about 0.4 mg I-1. Curve 1 excitation spectrum emission at 525 nm. Curve 2 emission spectrum excitation at 345 nm. FromKotaki and Yagi.128 (B) Indole in cyclohexane, T = 196 K. 1, Fluorescence excitation spectrum 2, fluorescence spectrum and 3, phosphorescence spectrum. From Konev.125...

Standard beads with broad-spectrum emission (e.g, FluoroSpheres, Dako Ltd., High Wycombe, UK)... 

Excitation Spectrum. Emission monochromator is maintained in a specific wavelength, and the data acquisition system scans the excitation monochromator measuring all wavelengths that the sample may excite. 

The energy of the MLCT excited state (F)oo( MLCT)) can be evaluated from the emission spectrum. Emission peak wavelength (le), emission quantum yields (0e), emission lifetimes (le), and reaction quantum yields of the photochemical ligand substitution reactions ( r) are summarized in Table III. The modification of the bipyridine ligand caused changes in. Boo( MLCT) as large as 2400 cm. ... 

Figure 3. Example of fluorescence excitation and hole-burning spectra of an intramolecular exciplex the fluorescence excitation spectrum ( emission sct at 395 nm, locally excited fluorescence) of 9-An-m-DMA (see Scheme 1 for structure) (b), along with two hole-burning spectra, (a) the probe laser set at 26644 cm and (c) the probe laser set at 26689 cm . The arrows in (a) indicate the bands used for the probe lasers. Adapted from Ref. [19b].

The known molecular constants are from the assignments of Weltner and McLeod (5). These authors observed the infrared spectrum, emission spectrum and visible absorption spectrum of C Si in matrix isolation. The matrix data allowed more certain... 

FIGURE 8.14. Absorbance spectrum PL excitation spectrum (—) (emission at 491 nm), PL emission spectrum (excitation at420 nm), and EL spectrum (squares) (ITO/m-... 

Absorption Spectrum 0 Emission Spectrum Emission Spectrum corrected for the sensitivity of the humer) eye... 

Figure 4.9 reports the change of the spectrum emission as radiation evolves through the wall of the inner glass tube (dotted lines). In this respect, the spectrum from the BL lamp remains almost unchanged after crossing the inner tube wall. The spectrum of the MR lamp is however, significantly modified, with more than half of the radiation lower than 300 nm absorbed by the reactor inner wall. 

Experimental < s measured in reflected shock waves with the spatially-integrated CO-0 flame spectrum emission method over a range of temperatures and for different values of rj, and normalized by 2[02], are displayed in Fig. 2.8. In accordance with equation (2.13), the data separate only with rj at higher temperatures. Variation of /2[02] with total gas concentration, predicted by equations (2.11) and (2.12) is seen inr] = 0-33 mixture data at the lowest temperatures. Also shown are recent infrared measurements which have extended the previously limited = 10 results up to nearly 2200 K, while yielding excellent agreement with the CO-0 data. 

Fig. 2.8. Experimental values of the logarithm of /2[02l against reciprocal reflected shock wave temperature for exponential growth data from various sources. 17 = 10 CO-0 flame spectrum emission measurements from Reference 62, a infrared emission measurements from Reference 74. rj = 0 33 C0 0 emission measurements from Reference 63 for various ranges of total reflected shock gas concentration and identical mole fractions of H2 and O2. 015 — 1 4 x lO moles liter . t 1 6 — 3-7 x 10 moles liter. 5-5 — 9 2 x 10 moles liter. Solid line = 9 5 x lO exp (—15 000/Rr) cm ...

The fluorescence spectrum (emission spectrum) of a sample is obtained by scanning M2 while keeping the excitation wavelength constant. Since the efficiency of M2 is wavelength dependent, and the detector (see below) also has a sensitivity that varies with wavelength, such a fluorescence spectrum is normally uncorrected , i.e., it will depend upon the instrument as well as the sample. The correction of emission spectra is less easy to achieve than for excitation spectra, and is less often performed, so published emission spectra often vary from instrument to instrument. At least three methods are available for emission correction. A sound but tedious method is to calibrate the emission system (i.e., M2 plus the detector) with a standard light source of known emission profile. Such devices are available from NIST and other standards bodies. Comparison of the output of the fluorescence spectrometer with the certified output of the lamp then provides a correction factor at each wavelength, which can be applied to subsequent sample spectra. A related technique is to... 

The fluorescence spectrum (emission spectrum) emitted from a discrete upper level Ek consists of discrete lines if the terminating lower levels / are bound states. A continuum is emitted if Ei belongs to a repulsive state of a molecule that dissociates. As an example, the fluorescence spectrum of the transition of the NaK molecule is shown in Fig. 2.14. It is emitted from a selectively excited level in a bound state that has been populated by optical pumping with an argon laser. The fluorescence terminates into a repulsive state, which has a shallow van der Waals minimum. Transitions terminating to energies Ek above the dissociation energy form the continuous part of the spectrum, whereas transitions to lower bound levels in the van der Waals potential well produce discrete lines. The modulation of the continuum reflects the modulation of the transmission probability due to the maxima and nodes of the vibrational wave function V vib( ) in the upper bound level [2.18]. 

There are two kinds of spectra. When light emitted from a source is analyzed, the spectrum obtained is called an emission SPECTRUM. Conversely, the spectrum obtained after light from some source has passed through a substance is known as an absorption spectrum. Emission spectra usually have a few colored lines—the emitted frequencies — on a black background. Absorption spectra show all colors interspersed with black lines—the absorbed frequencies. 

If a sample absorbs IR radiation at characteristic wavenumbers, it is capable of emitting radiation at these wavenumbers. A thin sample of a material will emit radiation with a spectrum very similar to its absorption spectrum. By ratioing the emitted radiation from the thin film to that from a black body at the same temperature, an emissivity spectrum is obtained which generally has the appearance of an inverted transmission spectrum. Emission spectra used to be collected from samples heated well above r.t., typically to 40-100°C (to minimise sample degradation), with a black-body source (e.g. graphite) at the same temperature as a reference. With FTIR instruments, emission spectra can also be recorded at room temperature. 

The fluorescence spectrum (emission spectrum) emitted from a discrete upper level Ek consists of discrete lines if the terminating lower levels Ef are bound states. A continuum is emitted if Ej belongs to a repulsive state of a molecule that dissociates. As an example, the fluorescence spectrum of the... 

Because fluorescence involves light-induced excitation followed by radiative decay, it is possible to enhance either, or both, depending on the overlap of the absorption spectrum, emission spectrum and plasmon resonance [20], the separation between... 

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