Spectroscopic line narrowing

To calculate the vibrational echo observable for a fixed laser frequency, >i, P(3) must be integrated over the spectroscopic line, g(to), or the laser bandwidth, whichever is narrower, and then the modulus square of the result must be integrated over all time since the observable is the integrated intensity of the vibrational echo pulse,... 

The m.p. line-narrowing technique has added an impressively long list of proton shielding tensors a to our knowledge of material properties. Complementary access to such tensors is to calculate them by quantum chemical methods. An important advantage of this approach is that, in addition to the symmetric constituent of a, it also yields the components of the antisymmetric constituent o " that are virtually inaccessible to measurements by spectroscopic means. So far only relaxation studies have provided experimental information about (Kuhn, 1983 Anet and O Leary, 1992). Note that these experiments were done on carbons. 

Constant-time imaging of H in solids has been applied in combination with MAS for line narrowing [Cor3, Cor4]. The images were recorded for a dynamically stressed poly(isoprene) phantom and of poly(butadiene) in two poly(butadiene)/poly(styrene) blends. Spectroscopic MAS imaging has also been tested on deuterated polymers to probe differences in molecular moblity from the lineshape of the rotary-echo envelope... 

P. Meystre, M.O. ScuUy, H. Walther, Transient line narrowing a laser spectroscopic technique yielding resolution beyond the natural linewidth. Opt. Commun. 33,153 (1980)... 

Fluorescence line-narrowing spectroscopy is a highly selective detection and identification technique for TLC (see Chapter 3 in Ref. 36). The combination of this spectroscopic technique with HPLC and TLC has been reported for the detection and identification of tetracene (178). 

Simply using a laser as a source does not take advantage of the full range of laser properties that are useful for spectroscopic purposes. The past decade and a half have witnessed the evolution of a host of laser based techniques which either have no readily identifiable equivalent in conventional spectroscopy or are difficult to carry out using the latter means. Two complementary techniques, fluorescence line narrowing (FLN) and hole burning, have found widespread uses in the spectroscopy of all phases principally as a form of homogeneous spectroscopy. 

Further spectroscopic experiments were carried out with an operating reactor using a bed of 1-mm catalyst beads [13]. A 3D experiment with one spectral and two spatial coordinates was carried out, yielding NMR spectra for each pixel of a 2D axial slice. Figure 5.4.7 shows several representative spectra selected from the entire data set. The NMR spectra of neat AMS [Figure 5.4.7(d)] and cumene [Figure 5.4.7(f)] are provided for comparison, they were experimentally detected for bulk liquid samples (lower traces with narrow lines) and their lines were then mathematically broadened to 300 Hz (upper traces) to account for the broadening in the... 

Treating vibrational excitations in lattice systems of adsorbed molecules in terms of bound harmonic oscillators (as presented in Chapter III and also in Appendix 1) provides only a general notion of basic spectroscopic characteristics of an adsorbate, viz. spectral line frequencies and integral intensities. This approach, however, fails to account for line shapes and manipulates spectral lines as shapeless infinitely narrow and infinitely high images described by the Dirac -functions. In simplest cases, the shape of symmetric spectral lines can be characterized by their maximum positions and full width at half maximum (FWHM). These parameters are very sensitive to various perturbations and changes in temperature and can therefore provide additional evidence on the state of an adsorbate and its binding to a surface. 

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