Spectra isotopic oxygen

In a mass spectrum, the ratios of isotopes give a pattern of isotopic peaks that is characteristic of a given element. For example, the mass spectrum of any corn ound containin carbon, hydrogen, nitrogen, and oxygen will show patterns of peaks due to the, 7C, 7N, gO, gO, and... 

Describe the spectrum produced on a photographic plate in a mass spectrograph if a mixture of the isotopes of oxygen ( O, nO, and lcO) is analyzed. Consider only the record for +1 and +2 ions. 

As evidence that this is so, consider that the element helium was detected in the sun before it was found on earth Though oxygen contains 0.2% of the oxygen-18 isotope on earth, it, too, was first detected in a solar spectrum. Two... 

The gas-phase structure of 1,3-dithietane 1-oxide (189) has been determined from its microwave spectrum and the spectra of eight isotopic modifications192. The ring is puckered, the angle between the two CSC planes being 39.3° with the oxygen equatorial. 

They found that the order for the M—0 stretching modes (M—0 force constants) was (02)Pd(02) > Pd(Oj) and (02)Ni(02) > Ni(02), and since the 0-0 force constant increased as the M-0 force constant decreased, reversibility could not be equated with shorter 0—0 bond length. To test the proposed isosceles model they predicted the various absorptions that would be expected on the basis of the symmetrical structure (a) and unsymmetrical structure (c), Fig. 8. If the isotopic ratio of 0 0 is 1 1, then three bands would be expected for structure (a), with relative intensities 1 2 1, and four bands would be expected for structure (c), with relative intensities 1 1 1 1, the two oxygen atoms now being in different environments. These workers 189) then obtained the IR spectrum for the cocondensation product from the reaction between nickel and O2 (4.2—10°K), in isotopic ratio 0 =1 1, and found three bands with relative inten-... 

A second type of defect is associated with boron or aluminum impurities that are present in SiCh- In porous glass Muha (129) observed a rather complex spectrum which results from hyperfine interaction with 10B and UB isotopes. The spectrum is characterized by g = 2.0100, g = 2.0023, an = 15 and a a. = 13 G for nB. The paramagnetic defect is apparently a hole trapped on an oxygen atom which is bonded to a trigonally coordinated boron atom. This center is irreversibly destroyed upon adsorption of hydrogen. 

Formally oxygen is also an A + 2 element. However, the natural abundance of the lsO isotope is only 0.2% of that of the main isotope ieO. That is why reliable calculation of the number of oxygen atoms based on the intensity of the isotopic peaks is hardly possible. Nevertheless, it is quite possible to estimate this number. Thus, if the intensity of the M + 2 peak in the mass spectrum of a sample with a low number of carbon atoms is higher than 0.5% relative to M+, this compound may contain one or more oxygen atoms. 

The relevance of oxygen and sulfur isotopic patterns is nicely demonstrated by the cluster ion series in fast atom bombardment (FAB) spectra of concentrated sulfuric acid, where the comparatively large number of sulfur and oxygen atoms gives rise to distinct isotopic patterns in the mass spectrum (Chap. 9). 

To study water exchange on aqua metal ions with very slow exchange of water molecules, an isotopic labeling technique using oxygen-17 can be used. A necessary condition for the applicability of this technique is that the life time, tm, of a water molecule in the first coordination shell of the ion is much longer that the time needed to acquire the 0-NMR spectrum. With modern NMR spectrometers and using enrichments up to 40% in the acquisition time can be as short as 1 s. 

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