Selective excitation SASS

There are some merits and demerits in each method. However, two-dimensional SASS and MAT seem to be the most convenient method to measure CSA spectra for real polymer samples. The selective excitation SASS is also very powerful in observing the CSA of a given C nucleus. 

Fig. 3.15. 50 MHz NMR spectra of BPAPC films measured at 25°C (a) CP/MAS (b) selective excitation MAS spectrum for the C5 carbon (c) selective excitation SASS spectrum for the C5 carbon and (d) descaled CSA spectrum for the C5 carbon (Ref. [33]).

F. Horii, T. Beppu, N. Takaesu, M. Ishida, Selective excitation SASS C NMR smdy of the phenylene motion of glassy polymers, Magn. Reson. Chem. 32 (1994) S30. 

The observation of selective fluorescence quenching by G C base pairs is consistent with the energetics of electron transfer (charge separation) from the bases to the singlet excited state Sa, which can be estimated using Weller s equation [26] ... 

This type of research uses pulsed and tunable la.sers as an excitation source. The rare earth ion is excited selectively with a laser pulse,and its decay is analyzed. The shape of the decay curve is characteristic of the physical processes in the compound under study. For a detailed review the reader is referred to the literature [1-3]. Here we give some results for specific situations. We assume that the object of our study consists of a compound of a rare earth ion S which contains also some ions A which are able to trap the migrating excitation energy of S by SA transfer. 

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