Note that for this model situation, it is by no means correct to estimate D as approximately L2/2t, as has often been assumed in the literature for the (admittedly slightly different) case of acceptor passivation. The correct D, equal to L2/2a2t, can even be orders of magnitude larger, if n(0)/nl is small (see Section 3 in III), since a— [n(0)/ i]1/2 in this limit. [Pg.266]

Woessner [11] proposed such a molecular motion model whereby p = 2, which is hereafter referred to as 2t model. In this model the C—H vector [Pg.60]

The a-helix (3.613) is not the only nonintegral spiral model. At least five others have been proposed 2.2t, 3.6u, 4.3u, 4.4i6 (7r-helix), 5.In (7-helix). Donohue (536) discusses all of these and ranks them in stability order 3.613 (a), 4.4ie ( ) and 2.2y, 5.In (7), 4.3h, 3.6u. The first three are very nearly equivalent in energy. Robinson and Ambrose (1733) carried out a somewhat different comparison, using integral spirals and the a-helix. They find the a-helix and a 2 model to be almost equivalent. [Pg.314]

Table 4.2. The basic parameters of the models under discussion for some adsorption systems. The dephasing (2f 4)) and the relaxation (2T 3)) contributions to the full spectral linewidth for local vibrations as well as the |

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