Deuterium isotope shift

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

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). 

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. 

Upheld shifts may also arise from substitution of an atom (e.g. H) by its heavier isotope (,e.g. 2H). The upheld shift follows from a lower potential energy of the ground state, hence an increased AE in eq. (3.4), and a reduction of bond distance. The influence of both effects will be to decrease the paramagnetic shielding term. Deuterium isotope shifts depend on the degree of deuteration and reach values of up to 1.5 ppm (Table 3.1). 

Stichtemath, A., R. Schweitzer-Stenner, W. Dreybrodt, R.S.W. Mak, X-Y. Li, L.D. Sparks, J.A. Shelnutt, C.J. Medforth, and K.M. Smith (1993). Macrocycle and substituent vibrational modes of nonplanar nickel(II) octaethyltetraphenylporphyrin from its resonance Raman, near-infrared-excited FT Raman, and FT-IR spectra and deuterium isotope shifts. J. Phys. Chem. 97, 3701. 

Measurements of the 1S-2S hydrogen-deuterium isotope shift have previously been suggested as a means to measure the proton/electron mass ratio.However, after recent improved measurements of this ratio,26 the uncertainty of the isotope shift is no longer dominated by the electron mass (35 kHz), but instead by nuclear size effects (180 kHz). 

Deuterium isotope shifts over at least six bonds were observed in rapidly interconverting p-thioxoketone tautomers [15] using C-nmr spectroscopy (Hansen et al., 1982). The observed effects are caused by a shift of the fast enol-enethiol equilibrium (27) when the chelating proton is substituted by deuterium. Deuterium prefers attachment to oxygen as compared to sulphur... 

Deuterium isotope shifts have been observed in the a-ketohydrazone/ azoenolic tautomeric compound [18] by and nmr spectroscopy (Hansen and Lycka, 1984). Besides large intrinsic isotope shifts, long range equilibrium isotope effects were observed which are caused by perturbation of the tautomeric equilibrium (30). The shifts increased on lowering the... 

A long range intrinsic deuterium isotope shift in 2,2-bis(trideuterio-methyl-5,5-dimethyl-l,3-dioxane [61] was observed by Anet and Dekmezian (1979). This molecule does not show an equilibrium isotope effect because the two rapidly interconverting chair isomers have exactly the same energy. 2-D-5.5-Dimethyl-l,3-dioxane, however, exhibits an isotope effect on the conformational equilibrium (Anet and Kopelevich, 1986a). Deuterium is preferred in the equatorial position (AG° = —49cal mol at 25°C). 

Deuterium isotope shifts over up to six bonds have been observed in the nmr spectrum of deuteriated cyclodecanones (Wehrli et al., 1978). The equilibrational origin of the observed long range effects was briefly discussed by Anet and Dekmezian (1979) and was explained in detail by Whipple et al. (1981). In the low temperature spectra of deuteriated cyclododecane iso-topomers Anet and Rawdah (1978) have also observed deuterium isotope effects which are likely to have a conformational origin and to arise from the lack of precise D4-symmetry in the preferred conformation of that hydrocarbon. 

C have essentially the same appearance as the spectra of the protio-ion except for intrinsic deuterium isotope shifts. This shows that the low temperature species is a static cation. 

The best method for observing the deuterium isotopic shift in the carbon spectrum is the differential shift technique using coaxial NMR tubes (142). This technique utilizes an inner and outer tube of equal volume. One tube contains the sample dissolved in the deuterated solvent, such as D2O or methanol-d4, whereas the other contains the corresponding protio-solvent. Those carbons experiencing isotopic shifts appear as double resonances in the broad-band proton-decoupled spectrum, one signal originating from the protio-sample and the isotopically shifted resonance from the deuterium-exchanged sample. 

Analysis of the deuterium isotopic shifts in the C-NMR spectrum has been particularly useful for sugar and oligosaccharide structural studies and spectral assignments (18, 151). Application of the differential isotope shift technique was used to study the tautomers of psicose, (33a-33d), in solution (Fig. 2.37a) (384). Signal assignments were made by comparison of calculated and observed cumulative isotope shifts. This method distinguished the C-1 and C-6 resonances. 

Fig. 2.37. a Differential deuterium isotope shifts for C-NMR assignments for the tautomers of psicose (33 a-33 d) (384). Figure shows the carbon chemical shifts recorded in D2O numbers in parentheses represent the differential induced shift caused by deuterium exchange, b Number of carbon signals predicted for cellobiose (34) in OMSO-d under partial exchange numbers in parentheses represent number of observed signals (62)... 

Doucet et described the determination of isotope ratios using LIBS in air at atmospheric pressure for partially resolved uranium-235-uranium-238 and hydrogen-deuterium isotope shift lines. A PLSl regression model could accurately predict the isotopic ratio under conditions where the application of traditional univariate approaches for hydrogen and uranium would not be achievable. 

Figure 2 Two-bond deuterium isotope shifts on the chemical shifts in V(CO)4 (assigned c/J. The asterisks...

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