| Autor: |
Whitaker, J., Ahn, F., Han, P., Williams, G. A., Taylor, P. C., Facelli, J. C. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 10/22/2003, Vol. 119 Issue 16, p8519, 7p, 4 Charts, 5 Graphs |
| Abstrakt: |
We present the results of nuclear quadrupole resonance (NQR) measurements in crystalline and glassy As[sub 2]Se[sub 3] and As[sub 2]S[sub 3]. As a function of pulse separation, the decays of the NQR Hahn echoes following a 90°–180° pulse sequence exhibit damped oscillations superimposed on an exponential decay. These damped oscillations can be explained by an indirect coupling (J coupling) between two As nuclei through the polarized electrons on the chalcogen atom. Experimental values of the J couplings were obtained from the periods of the oscillations and calculations of the most probable transitions using second-order perturbation theory. The value estimated by this method for the [sup 2]J([sup 75]As–S–[sup 75]As) in crystalline As[sub 2]S[sub 3] compares well with empirical estimates, which are obtained using an existing value of [sup 2]J([sup 31]P–S–[sup 31]P) and known scalings with atomic number from the literature. Unfortunately, there is insufficient experimental data on [sup 2]J(X–Se–X) couplings to make any empirical estimate of [sup 2]J([sup 75]As–Se–[sup 75]As). © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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