Line width method

McConnell and Weaver, using the nmr line width method, have obtained a value for the observed rate coefficient, for the reaction in 12 M hydrochloric acid media, of 5 x 10 l.mole . sec. The width of the Cu NMR line from copper(I) ( 1 M) was observed in the presence of copper(II) (10 to 10 M). In this media the exchanging species are probably CuCl4 and CuCls . Optical interaction effects have been observed in mixtures of Cu(I) and Cu(II) in chloride media. ... 

Attempts at investigation of the kinetics of exchange in triiodide have been made using nmr line-width methods . It is concluded in the most recent publication that the relaxation times observed to date for CI, C1, Br and l are all probably due to relaxation, viz. 

Determination of average nanoparticle size by line width method... 

A particle of less than 200 nm can widen the diffraction peak, and the finer the nanoparticle, the wider the peak is, and therefore the method is also called as the line width method. This method can be calculated by using the following equation ... 

Although more direct than photoresist, this method, limited to line widths of 250—380 p.m (10—15 mils) because of the limits of screen fabrication, is used primarily for low cost print-and-etch and plated PWBs (5). 

In principle all the X-ray emission methods can give chemical state information from small shifts and line shape changes (cf, XPS and AES in Chapter 5). Though done for molecular studies to derive electronic structure information, this type of work is rarely done for materials analysis. The reasons are the instrumental resolution of commercial systems is not adequate and the emission lines routinely used for elemental analysis are often not those most useftil for chemical shift meas-ure-ments. The latter generally involve shallower levels (narrower natural line widths), meaning longer wavelength (softer) X-ray emission. 

It would appear that measurement of the integrated absorption coefficient should furnish an ideal method of quantitative analysis. In practice, however, the absolute measurement of the absorption coefficients of atomic spectral lines is extremely difficult. The natural line width of an atomic spectral line is about 10 5 nm, but owing to the influence of Doppler and pressure effects, the line is broadened to about 0.002 nm at flame temperatures of2000-3000 K. To measure the absorption coefficient of a line thus broadened would require a spectrometer with a resolving power of 500000. This difficulty was overcome by Walsh,41 who used a source of sharp emission lines with a much smaller half width than the absorption line, and the radiation frequency of which is centred on the absorption frequency. In this way, the absorption coefficient at the centre of the line, Kmax, may be measured. If the profile of the absorption line is assumed to be due only to Doppler broadening, then there is a relationship between Kmax and N0. Thus the only requirement of the spectrometer is that it shall be capable of isolating the required resonance line from all other lines emitted by the source. 

De Waard and Perlow [54] observed a marked influence of the method of preparation of source and absorber on both the line width and the depth of resonance. For instance, the line width was found to be 2.7 pm s for a powdered ZnO absorber as compared to 0.8 pm s for a sintered one. 

This chapter deals mainly with (multi)hyphenated techniques comprising wet sample preparation steps (e.g. SFE, SPE) and/or separation techniques (GC, SFC, HPLC, SEC, TLC, CE). Other hyphenated techniques involve thermal-spectroscopic and gas or heat extraction methods (TG, TD, HS, Py, LD, etc.). Also, spectroscopic couplings (e.g. LIBS-LIF) are of interest. Hyphenation of UV spectroscopy and mass spectrometry forms the family of laser mass-spectrometric (LAMS) methods, such as REMPI-ToFMS and MALDI-ToFMS. In REMPI-ToFMS the connecting element between UV spectroscopy and mass spectrometry is laser-induced REMPI ionisation. An intermediate state of the molecule of interest is selectively excited by absorption of a laser photon (the wavelength of a tuneable laser is set in resonance with the transition). The excited molecules are subsequently ionised by absorption of an additional laser photon. Therefore the ionisation selectivity is introduced by the resonance absorption of the first photon, i.e. by UV spectroscopy. However, conventional UV spectra of polyatomic molecules exhibit relatively broad and continuous spectral features, allowing only a medium selectivity. Supersonic jet cooling of the sample molecules (to 5-50 K) reduces the line width of their... 

IR and Raman line shapes have been measured for H0D/H20. They peak near 2500 cm 1 and have line widths in the 160 to 180 cm 1 range. Corcelli et al. [151] calculated these line shapes using the approaches described in Section III.C, for the SPC/FQ model, for temperatures of 10 90°C, finding quite good agreement with experiment. More recently, we have extended the method involving the quadratic electric field map for HOD/D20 [98] to HOD/H20 [52] and have calculated IR and unpolarized Raman line shapes. These line shapes, in comparison with experimental line shapes [12, 52], are shown in Fig. 7. Agreement between theory and experiment is excellent for both the IR and Raman. 

For the measurement of cross-correlated relaxation rates, there are mainly three methods that have been used in practice. In the /-resolved constant time experiment, the multiplet Hnes exhibiting differential relaxation are resolved by the f couplings, and the line width is translated into intensity in a constant time experiment (Fig. 7.19a,d). In the J-resolved real time experiment the line width of each multiplet line is measured instead (Fig. 7.19b, d). This experiment has been applied so far only for the measurement of... 

Alkali Iodides. Figure 8 shows the experimental data obtained for the recoilless fraction, /, at 80°K. The area (13), line width (13), and the temperature (26) methods have all been used to analyze these data. Uncertainties in the background corrections (13) are caused by rather large errors. However, the striking feature is that the recoilless fraction changes only little from Lil to Csl. 

The possibilities afforded by SAM-controlled electrochemical metal deposition were already demonstrated some time ago by Sondag-Huethorst et al. [36] who used patterned SAMs as templates to deposit metal structures with line widths below 100 nm. While this initial work illustrated the potential of SAM-controlled deposition on the nanometer scale further activities towards technological exploitation have been surprisingly moderate and mostly concerned with basic studies on metal deposition on uniform, alkane thiol-based SAMs [37-40] that have been extended in more recent years to aromatic thiols [41-43]. A major reason for the slow development of this area is that electrochemical metal deposition with, in principle, the advantage of better control via the electrochemical potential compared to none-lectrochemical methods such as electroless metal deposition or evaporation, is quite critical in conjunction with SAMs. Relying on their ability to act as barriers for charge transfer and particle diffusion, the minimization of defects in and control of the structural quality of SAMs are key to their performance and set the limits for their nanotechnological applications. 

EPR spectroscopy is the most important method for determining the structures of transient radicals. Information obtained from the EPR spectra of organic radicals in solution are (i) the centre position of the spectra associated with g factors, (ii) the number and spacing of the spectral lines related to hyperfine splitting (hfs) constants, (iii) the total absorption intensity which corresponds to the radical concentration, and (iv) the line widths which can offer kinetic information such as rotational or conformational barriers. The basic principles as well as extensive treatments of EPR spectroscopy have been described in a number of books and reviews and the reader is referred to this literature for a general discussion [28 30]. 

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