Isotope shift hydrogen

Ionic dissociation of carbon-carbon a-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153 Ions, organic, charge density-NMR chemical shift correlations, 11,125 Isomerization, permutational, of pentavalent phosphorus compounds, 9, 25 Isotope effects, hydrogen, in aromatic substitution reactions, 2,163... 

A number of other models were considered and tested (for example, direct B—H bonding). The most significant test was the IR vibrational spectrum, where a sharp absorption band at 1875 cm-1 was found, corresponding to the Si—H stretch mode softened by the proximity of the B-atom. Had the hydrogen been bonded to boron, a sharp absorption band at 2560 cm-1 would have been expected. Also, Johnson (1985) showed that deuteration produced the expected isotopic shift. The most definitive and elegant proof of the correctness of the Si-H-B bonding model was provided by Watkins and coworkers (1990), on the basis of a parametric vibrational interaction between the isotopes D and 10B. 

Fig. 12.7 An unusually long range (10-bond) secondary D isotope shift IE on an [19F] NMR. The H/D chemical shift isotope effect due to substitution at an OH — N hydrogen bond sited ten bonds away from a para-F is 11 ppb (Hansen, P. E. et al. Acta Chim. Scandanavia 51,881 (1997))...

Fig. 6 Variation of the deuterium isotope-shift ratio, Voh/Vod> " th hydrogen-bond length Rq. o (adapted from Novak, 1974).

Fig. 7 Ir isotope shift associated with weak, strong and very strong hydrogen bonds.

Fig. 11 Isotopic shift associated with phase change temperature and hydrogen bond length (adapted from Ichikawa, 1981).

Numerically the contribution in (4.24) is below 1 kHz. Due to linear dependence of the recoil correction on the electron-nucleus mass ratio, the respective contribution to the hydrogen-deuterium isotope shift (see Subsect. 12.1.7 below) is phenomenologically much more important, it is larger than the experimental uncertainty, and should be taken into account in comparison between theory and experiment at the current level of experimental uncertainty. 

Prom the practical point of view, the difference between the results in (5.6) and (5.8) is about 0.18 kHz for lA level in hydrogen and at the current level of experimental precision the distinctions between the expressions in (5.6) and (5.8) may be ignored in the discussion of the Lamb shift measurements. These distinctions should, however, be taken into account in the discussion of the hydrogen-deuterium isotope shift (see below Subsect. 12.1.7). 

Experimental data on the deuterium-hydrogen isotope shift (see Table 12.4 below) have an accuracy of about 0.1 kHz and, hence, a more accurate theoretical result for the polarizability contribution is required. In order to obtain such a result it is necessary to go beyond the zero range approximation, and take the deuteron structure into account in more detail. Fortunately, there exist a number of phenomenological potentials which describe the properties of the deuteron in all details. Some calculations with realistic proton-neutron potentials were performed [40, 41, 42, 43]. The most precise results were obtained in [43]... 

We see that the difference of these corrections gives an important contribution to the hydrogen-deuterium isotope shift. 

The main contribution to the hydrogen-deuterium isotope shift is a pure mass effect and is determined by the term E in (3.6). Other contributions coincide with the respective contributions to the Lamb shifts in Tables 3.2, 3.3, 3.7, 3.9, 4.1, 5.1, and 6.1. Deuteron specific corrections discussed in Subsubsect. 6 and collected in (6.16), (6.28), (6.29), and (6.37) also should be included in the theoretical expression for the isotope shift. 

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