Band excitation

Whereas currently most studies deal with azides, a similar effort devoted to other metal salts such as nitrates and chlorates would be an important step toward understanding electrical initiation of pyrotechnics, and conversely to making possible safe, non-expl igniters. For instance, a study by Maycock (Ref 4) shows that those azides, perchlorates, and nitrates in which the solid state shows absorption on the long wavelength side of the anionic excitation band in soln, are the most unstable members of the respective series. Consequently, there is a direct relationship between the absorption spectra of pyrotechnic oxidizers and their respective sensitivities... 

The most commonly used dye in fluorescence studies on nucleic acids is ethidium bromide. The dye has broad excitation bands centered around 280 and 460 nm and a strong emission around 600 nm. When the dye hinds to DNA by an intercalative mechanism, its emission is greatly enhanced and slightly shifted in wavelength. In the simplest case with ethidium bromide saturating intercalating sites,... 

Photophysical Processes in Dimethyl 4,4 -Biphenyldicarboxy-late (4,4I-BPDC). The ultraviolet absorption spectrum of dimethyl 4,4 -biphenyldicarboxyl ate was examined in both HFIP and 95% ethanol. In each case two distinct absorption maxima were recorded, an intense absorption near 200 nm and a slightly less intense absorption near 280 nm. The corrected fluorescence excitation and emission spectra of 4,4 -BPDC in HFIP at 298°K shows a single broad excitation band centered at 280 nm with a corresponding broad structureless emission band centered at 340 nm. At 77°K, the uncorrected phosphorescence spectra shows a single broad structureless excitation band centered at 298 nm, and a structured emission band having maxima at 472 and 505 nm with a lifetime, t, equal to 1.2 seconds. 

Photophysical Processes in Pi butyl 4,4 -Sulfonyldibenzoate (4,4 -SD). The UV absorption spectra of dibutyl 4,4 -sulfonyl-dibenzoate (4,4 -SD) in both HFIP and 95% ethanol showed similar absorptions. The corrected excitation and emission fluorescence spectra of 4,4 -SD in HFIP at 298°K showed a structured excitation with band maxima at 236, 286, and 294 nm and a structured emission exhibiting band maxima at 322, 372, and 388 nm. The uncorrected excitation and phosphorescence spectra of 4,4 -SD in a 95% ethanol glass at 77°K displayed excitation band maxima at 268, 282, and 292 nm with strong phosphorescence emission with band maxima at 382, 398, and 408 nm with a mean lifetime (t) of 1.2 sec. 

An excitation band maximum was found at 312 nm with a broad, structureless band centered at 452 nm found in the emission spectra. The phosphorescence mean lifetime (t) was found to be 1.2 sec. 

The first intravascular sensor for simultaneous and continuous monitoring of the pH, pC>2, and pCC>2 was developed by CDI-3M Health Care (Tustin CA)14 based on a system designed and tested by Gehrich et al.15. Three optical fibres (core diameter = 125 pm) are encapsulated in a polymer enclosure, along with a thermocouple embedded for temperature monitoring (Figure 3). pH measurement is carried out by means of a fluorophore, hydroxypyrene trisulfonic acid (HTPS), covalently bonded to a matrix of cellulose, attached to the fibre tip. Both the acidic ( eXc=410 nm) and alkaline ( exc=460 nm) excitation bands of the fluorophore are used, since their emission bands are centred on the same wavelength (/-cm 520 nm). The ratio of the fluorescence intensity for the two excitations is measured, to render the sensor relatively insensitive to fluctuations of optical intensity. 

Chapter 3 is devoted to dipole dispersion laws for collective excitations on various planar lattices. For several orientationally inequivalent molecules in the unit cell of a two-dimensional lattice, a corresponding number of colective excitation bands arise and hence Davydov-split spectral lines are observed. Constructing the theory for these phenomena, we exemplify it by simple chain-like orientational structures on planar lattices and by the system CO2/NaCl(100). The latter is characterized by Davydov-split asymmetric stretching vibrations and two bending modes. An analytical theoretical analysis of vibrational frequencies and integrated absorptions for six spectral lines observed in the spectrum of this system provides an excellent agreement between calculated and measured data. 

UV photoluminescence Emission bands at 495 and 430 nm with the corresponding excitation bands at 250 and 300 nm, respectively... 

Because of the coexistence of the multiple effective RF fields, the RF interference appears in each excitation band.25 The interference may be neglected if the strengths of any two interacting RF fields are much weaker than the frequency separation between them. Otherwise, the RF interference is noticeable and needs to be taken into account in the calculation of the excitation profile. 

According to Eqs. (8) and (9), the effective RF fields are scaled unsymmet-rically (in respect to the sideband number n) by the scaling factor Xn, in response to the unsymmetrical excitation profile. When K<0, the nth effective RF field becomes negative, which corresponds to a sign change of the operator Ix from positive to negative, or equivalently, a 180° phase shift is introduced to the nth effective RF field. Consequently, a phase inversion occurs in the transverse magnetization of the nth excitation band. 

All the effective RF fields created by a PIP are shifted from the carrier frequency fa. To calculate the rath excitation band for example, a transformation from the rotating frame to a new one (or the second rotating frame) is often needed, where the rath field plays the role of a new carrier. This transformation can be achieved by a unitary operator of1... 

It leads to unsymmetrical excitation bands in respect to the sideband number n. However, the scaling factor remains unchanged if both the side band number n and the phase increment A ip change sign... 

Table 2. The frequencies f , phases 6 , scaling factors Xn of the effective RF fields and the amplitudes A of the excitation bands created by a Gaussian shaped PIP10 (0°, 144°, 40ps, fi(k), 125) with /i(fc) = 0.1577 exp[ — 0.002 x (k —63)2] kHz and a total phase increment 2nA/r = 2mn...

Fig. 6. Computer simulated excitation bands (n = — 2 to 2) by a Gaussian shaped PIP (Table 2), where the centre band (w = 0) is shifted to 10 kHz and the spectral width of each band is 4 kHz. The amplitudes of the profiles are asymmetric in response to the asymmetric effective RF fields.

Table 5. The frequencies / , phases 6 , scaling factors Xn of the effective RF fields, and the amplitudes A of the excitation bands created by a DANTE sequence...

In the case of total transfer (T = 1), these two spectra are identical after normalization at the same height. But for any value of x less than 1, the excitation band corresponding to the donor is relatively lower than the absorption band. The comparison of the absorption and excitation spectra can be done at two wavelengths 7p and 7a corresponding to the absorption maxima of the donor and the acceptor, respectively. If there is no absorption of the donor at 7A, we get... 

Approximate linear dependence of AO-based sets is always a numerical problem, especially in 3D extended systems. Slater functions are no exceptions. We studied and recommended the use of mixed Slater/plane-wave (AO-PW) basis sets [15]. It offers a good compromise of local accuracy (nuclear cusps can be correctly described), global flexibility (nodes in /ik) outside primitive unit cell can be correct) and reduced PW expansion lengths. It seems also beneficial for GW calculations that need low-lying excited bands (not available with AO bases), yet limited numbers of PWs. Computationally the AOs and PWs mix perfectly mixed AO-PW matrix elements are even easier to calculate than those involving AO-AO combinations. 

Table 6. Ratio of electric to magnetic dipole emission intensity and position of the lowest excitation band for some Eu +-activated ABO4 compounds [after Ref. (33))...

Compound Crystal structure 5Do 5Do Fi Maximum lowest excitation band (IcK)... 

Table 11. Position of the first strong excitation bands of the luminescence of the WO and the UO octahedra in several host lattices. Values in kK...

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