Isotopic double substitution

Two special procedures employed in structure calculations will be mentioned here. One is the double substitution method introduced by Pierce26 and used for the determination of the coordinates of atoms near a principal inertial plane, which is the situation for which the Kraitchman equations become unreliable. In Pierce s method rotational constants must be available for four isotopic species, two of which are... 

The principal drawbacks of the double substitution method are the extra isotopic substitution required and the highly accurate rotational constants required for the second differences. While Pierce s method has been very successful in some cases, it has not had widespread usage. 

Fig. 7. Measured and simulated absolute magnitude 2D-IR rephasing spectra of a 25mer a-helix with double isotope substitutions denoted as [ 3C= 60, l3C= 80]. (A) [12,13], (B) [11,13], Experimental condition D20-phosphoric acid buffer at 0° C. (C) and (D) are corresponding simulations.

Further improvement of the structural and optical properties of the PLD Bragg mirrors was achieved by substituting ZnO by yttria stabilized zir-conia (YSZ, with typically 9 at. % Y2O3), as demonstrated in Fig. 7.29. A considerable increase of the maximum reflectivity of the Bragg structures from about 90-99% was realized by doubling the number of YSZ-MgO layer pairs from 5.5 to 10.5 as shown in Fig. 7.29 (top). The experimentally obtained single layer thicknesses of the 5.5 and 10.5 pair structure are given in the caption and show smaller variation compared to the MgO-ZnO structure of Fig. 7.28. Indeed, the SNMS isotope intensity depth profile... 

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