Excitations spectrum

The room temperature Raman spectrum excited in pre-resonance conditions [351 indeed shows bands at 169 cm-1 and 306 cm, which are in agreement with the modes observed in the fluorescence spectrum and that have been assigned by ab initio calculations to totally symmetric vibrations jl3). 

Tabic 6-5. Comparison of (he aK vibrational modes in the ground and excited states. The totally symmetric vibrations of the ground stale measured in tire Raman spectrum excited in pre-resonance conditions 3S] and in the fluorescence spectrum ]62 ate compared with the results of ab initio calculations [131- The corresponding vibrations in the excited stale arc measured in die absorption spectrum. 

Fig. 1-15. The molybdenum spectrum excited by 35-kv electrons and by the polychromatic beam from a 35-kv x-ray tube. With x-ray excitation, most of the energy appears in the characteristic lines. With electron excitation, most of it is wasted in the continuous spectrum.

In most ordinary cases, the disadvantages of x-ray excitation are more than compensated by the absence of the disadvantages peculiar to electron excitation, by the great convenience of Coolidge tubes (1.3), and by the absence of the large background count to which the continuous x-ray spectrum excited by electrons gives rise (1.5). 

The spectrum excited by an electrical discharge through gas at low pressme can be studied with two simple types of spectrum tube seen in Figure 75. These tubes also act as weak sources of certain radiations, such as monochromatic light for an optical spectrometer. The... 

Soon after Dennison had deduced from the specific-heat curve that ordinary hydrogen gas consists of a mixture of two types of molecule, the so-called ortho and para hydrogen, a similar state of affairs in the case of iodine gas was demonstrated by direct experiment by R. W. Wood and F. W. Loomis.1 In brief, these experimenters found that the iodine bands observed in fluorescence stimulated by white light differ from those in the fluorescence excited by the green mercury line X 5461, which happens to coincide with one of the iodine absorption lines. Half of the lines are missing in the latter case, only those being present which are due to transitions in which the rotational quantum number of the upper state is an even integer. In other words, in the fluorescence spectrum excited by X 5461 only those lines appear which are due to what we may provisionally call the ortho type of iodine molecule. 

A discussion on steady state fluorescent monitoring necessitates a distinction between spectroscopic and photometric measurements. The former involves a grating-based spectrofluorometer where full spectrum excitation and emission multivariate spectra are acquired. In contrast a filter photometer involves optical elements (e.g., optical Alters) to isolate excitation and emission bands thereby resulting in a univariate output emission response. 

EMISSION SPECTRUM ACTION SPECTRUM EXCITATION SPECTRUM FLUORESCENCE Empirical rate equations,... 

FIGURE 6.19 Vibrational spectra of vanillin in isopropanol solntion. Bottom panel experimentally measnred CARS spectrum (1064 nm and continuum excitation, 1064 nm probe). Middle panel retrieved Raman spectrum. Top panel experimentally measured spontaneous Raman spectrum (excitation wavelength 532 nm). The acquisition time for CARS spectrum was 100 times shorter than for spontaneous Raman. The incident powers were set at approximately the same level. 

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...

Curl et al. (255) have analyzed the fluorescence spectrum excited by the 4765 A Ar+ laser line. The A2A2 state produced must predissociate appreciably at this wavelength since fluorescence is very weak and some decomposition products are found. Since the photon energy used (2.601 eV) is higher than D0(OC1 — O) = 2.50 cV, dissociation is expected. 

Fig. 4.9. Normal Raman spectrum (excitation intensity 1.8 x 106 W/cm2, 10 s acquisition time) of intact rye pollen grain and SERS spectrum (excitation intensity 1.8 x 105 W/cm2, Is acquisition time) of rye pollen supernatant excited at 785nm...

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-... 

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

Figure 2 shows the PL spectrum of Ti-MCM-48 (Anpo and Che, 1998), which together with its absorption spectrum (excitation spectrum), is in good agreement with those previously observed for highly dispersed... 

Figure 26 Emission spectra (PL, EL) in PC at room temperature of 40 wt% TPD donor solution with a 40 wt% of PBD acceptor added. The photoluminescence (PL) spectrum excited at 360 nm, the electroluminescence (EL) spectra (I, II) originate from the recombination radiation in a 60 nm thick film, taken at two different voltages. Absorption (Abs) and PL spectra (excitation at 360 nm) of (75wt% TPD 25wt% PC) and (75wt% PBD 25wt% PC) spin-cast films are given for comparison. Molecular structures of the compounds used are given in the upper part of the figure TPD [N,Nf-diphenyl-A v/V/-bis(3-methylphenyl)-l,l -biphenyl-4,4 diamine PBD [2-(4-biphenyl)-5-(4- er .-butylphenyl)l,3,4-oxadiazole PC[bisphe-nol-A-polycarbonate]. Adapted from Ref. 112.

Most lanthanide ions absorb electromagnetic radiation, particularly in the visible region of the spectrum, exciting the ion from its ground state to a higher electronic state, as a consequence of the partly filled 4f subshell. The f-f transitions are excited both by magnetic dipole and electric dipole radiation. Normally the magnetic dipole transitions would not... 

Figure 3.3-5 Transmission of a quartz fiber in the near-infrared region, r is the transmittance of a fiber with a length of 1 km, below are the ranges of the Raman spectrum excited by the HeNe laser at 623 and the Nd YAG laser at 1064 nm.

Figure 3.5-3 Linear decadic absorption coefficient of H2O, D2O, Ethanol, and Cyclohexane in the near infrared region. Insertion range of the Raman spectrum, excited by the NdrYAG laser with radiation of A = 1064 nm.

If the spatial resolving power has to be high, then the Raman radiation must be observed through microscope objectives (Fig. 3.5-10 b). Unfortunately, these objectives have a somewhat lower optical conductance than the regular sample arrangement (Schrader, 1990). As a result, the observed Raman spectrum is also considerably weaker. A microscope may be connected to the spectrometer by a mirror system or by optical fibers, as shown in Fig. 3.5-10 b. Optical fibers are e.specially useful for NIR FT Raman spectroscopy, because the transmission of the fibers may be at its maximum exactly in the range of a Raman spectrum excited by a Nd YAG laser (Fig. 3.3-5). 

Figure 3.5-14 Thermal emission Relative signal, recorded by a Germanium detector of a sample, thickness 1 cm, with the absorption properties of water (broken lines) and of a black body (full lines) in the range of the Raman spectrum excited with the Nd YAG laser at 1064 nm.

Fig. 26. Photoluminescence spectra of the molybdenum oxide catalyst anchored to Si02 (molybdenum oxide/Si02) at 77 K (a) and at 298 K (b) and their excitation spectrum. Excitation wavelength at 280 nm emission monitored at 520 nm [reproduced with permission from Anpo...

Fig. 21. Photoemission spectra of Nao.erWOsCOOl) (2x1) excited at the different photon energies indicated. The dashed line and arrow in the spectrum excited at 100 eV emphasise the feature attributed to the a bonding level in peroxide-like surface dimers. Adapted from ref. 298.

Figure 1. Luminescence spectrum (excited at 277 nm) and TEM image of Gd20j Tb nanoparticles produced by laser ablation.

Radiation in the far (long-wavelength) infrared and microwave regions of the electromagnetic spectrum excites rotational states of molecules. In order to absorb radiation, the molecule must have a permanent dipole moment. Moreover, for a heteronuclear diatomic molecule, absorption of light is possible only between... 

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

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