Isotopic structure

The largest class of meteorite finds is stony meteorites, made principally of stone. The general stony classification is divided into three subclasses called chondrites, carbonaceous chondrites and achondrites, and it is at this level of distinction at which we will stop. Before looking at their mineral and isotopic structure in more detail, it is useful to hold the composition of the Earth s crust in mind here for comparison. The Earth s crust is 49 per cent oxygen, 26 per cent silicon, 7.5 per cent aluminium, 4.7 per cent iron, 3.4 per cent calcium, 2.6 per cent sodium, 2.4 per cent potassium and 1.9 per cent magnesium, which must have formed from the common origin of the solar system. 

Podosek, F. A. (1978) Isotopic structure in solar system materials. Ann. Rev. Astron. Astro-phys., 16, 293-334. 

The internal standard should show physical and chemical properties that are as close as possible to those of the molecule that has to be measured. It must be pure, absent from the sample and, of course, inert towards the compounds in the sample. The internal standards can be classified into three categories structural analogues that are labelled with stable isotopes, structural homologues and compounds from the same chemical family. These various types of internal standards are classified here in descending order according to their usefulness and their price. In fact, the starting material for labelled compounds is fairly... 

The fundamental frequencies correspond to isotopomers, containing the most abundant isotopes, or represent the effective values if the isotopic structure has not been observed. 

Figure 6 The 780-720cm of the IR ahsorption spectrum of trans-02Mo(CO)4. The two bands are assigned to Vas( 0=Mo= 0) and Vas( 0=Mo= 0). Both clearly exhibit Mo isotope structure. (Reprinted with permission from Ref 11a 1984 American Chemical Society)...

Furthermore, isotopic structure and hyperfine structure, and also resonance broadening, resulting from the interaction between radiating and non-radiating atoms of the same species, and Stark broadening, resulting from interaction with electrical fields, contribute to the physical widths of the spectral lines. 

Low frequency i.r. spectra have been obtained for Mo(CO) in Ar, Nj, and O, matrices in which the v, band shows metal isotopic structure in the N2 matrix which can be reproduced by computer simulation. I.r. evidence is presented in which Mo(CO)g physically adsorbed onto a y-alumina surface in vacuo [Mo(CO) (ads)] reversibly forms surface subcarbonyl species, reaction (6)... 

Figure 12. Isotope structure of the 5887.9-A line of neodymium (a) and the 5988.6-A line of dysprosium (b). The abscissa in each figure is relative frequency in gigahertz (11).

Borg SG, DePaolo DJ, Smith BM (1990) Isotopic structure and tectonics of the central Transantarctic Mountains. J Geophys Res 95 6647-6667... 

Figure 8. TWo-photon spectrum of the transition 4s Cal, showing isotopic structure.

---