Oxygen-18 isotope shifts

Isotope Shifts. - Oxygen-induced isotope shifts on Tc shielding in the pertechnetate ion have been explored by Cho et a/. The variations in the Tc shielding in isotopomers involving 0, 0 and 0 have been predicted by making use of a relativistic spin-orbit density functional theory combined with a solvated ion approach. A single atom substitution, for example, 0 0 in... 

Most hot spring waters have deuterium contents similar to those of local precipitation, but are usually emiched in as a result of isotopic exchange with the country rock at elevated temperatures. The magnitude of the oxygen isotope shift depends on the O-isotope composition of both water and rock, the mineralogy of the rock, temperature, water/rock ratio, and the time of interaction. 

The ultraviolet absorption spectrum of formaldehyde consists of many sharp discrete bands of Doppler width. The isotopic shifts due to C and O atoms are sometimes 5 to 10 cm-1 in the 3000 to 3100 A region [see Moore (715)]. Hence, it is possible to selectively excite a specific carbon or oxygen isotopic species in mixtures of other isotopic species. 

The isotope shift observed with chemisorbed C130 indicated that the force constant, k, of the platinum-carbon stretching vibration was 4 X 106 dynes/cm. and the carbon-oxygen force constant, k2, was 16 X 106 dynes/cm. Use of these values of the force constants in the equation (60)... 

Quade J, Cerling TE, Bowman JR (1989b) Development of the Asian Monsoon revealed by marked ecological shift in the latest Miocene in northern Pakistan. Nature 342 163-166 Quade J, Cater JML, Ojha TP, Adam J, Harrison TM (1995) Dramatic carbon and oxygen isotopic shift in paleosols from Nepal and late Miocene environmental change across the northern Indian sub-continent. Geol Soc Am Bull 107 1381-1397... 

Now we shall point out on an experimental confirmation concerning the role of a cooperative motions in formation of the R-band in water. In a recent paper [62] it was inferred from an isotope shift of the R-band that the oscillations to this band are stipulated by molecules deformations. Next, in view of work [63], where the Raman spectra of water substituted with respect to hydrogen and oxygen were studied, one can conclude that the isotope shift is greater for the oxygen substitution. This result means that the oscillations pertinent to the... 

Subsequently, RR was used to successfully detect structural changes between the oxidized and reduced forms of both DMSOR and BSOR that are consistent with the proposed oxygen atom transfer mechanism of the catalytic reaction (95, 97). These experiments make use of the readily measurable isotopic shifts in vibration frequency between ieO=Mo and lsO=Mo to follow the fate of the oxygen atom removed from DMSO (or BSO) by the Mo. In this way, the clean transfer of 180 from DMSlsO to Mo(IV) to yield the oxidized form of the active site as Mo(VI)=180 was directly observed as well as the substrate-bound intermediate, (DMS180)Mo(IV). Further discussion of the technique of RR applied to metal dithiolenes and dithiolene-containing enzymes is included in Chapter 4 in this volume (98). 

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