Isotopomers of oxygen

Other isotopomers of oxygen have been studied, notably 160170 by Miller and Townes [122], 18C>2 by Steinbach and Gordy [125] and 160180 by Amano and Hirota [119]. Measurements of the predominant isotopomer in its v = 1 level have also been described by Amano and Hirota [119], Values of the molecular constants obtained from these studies are listed in table 10.9. In the case of160170 magnetic hyperfine constants for 170, which has a spin of 5/2, have been determined by Miller and Townes [122] we will come to these studies shortly, but first examine how the transition frequencies listed in table 10.8 depend upon the values of the molecular parameters listed in table 10.9. 

Table 10.9. Molecular parameters (in MHz) determined for different isotopomers of oxygen...

Other isotopomers of oxygen have been studied, notably by Miller and... 

The crystal structure of the complex formed between carboxypeptidase Aa (abbreviated CPA) and glycyltyrosine (Gly-Tyr) has been refined to 2.0 A by Lipscomb et at. (444, 445) and it reveals (Fig. 90) interactions between the amide carbonyl oxygen and the catalytically essential Zn, and between the amide nitrogen and the hydroxyl of tyrosine-248 (Tyr-248). Scott et al. (443) synthesized both the [13C]amido (90% enriched) and amido[l3C, 15N]amido (90% and 99% enriched, respectively) isotopomers of Gly-Tyr. They then proceeded to probe the hydrolysis by a series of l3C and l5N high-resolution solid-state NMR spectra. 

Experimental studies permit some tests of these ideas. For example, the universality of the effect among all types of ozone isotopomers is seen in oxygen mixtures heavily enriched in and [18] and compared with theory in Figure 2.3 [12,13]. It is also seen in Figure 2.4, the points at AZPE = 0 being about 18% lower than those for the asymmetric cases. The effect of pressure on the MIF from 10 to 10 bar [16,17] has been measured and the theory tested by comparison with the data [12,13]. We note that at higher pressures all of the O3 formed is collisionally deactivated to form O3 and so the anomaly reflected in the differences in lifetimes of the symmetric and asymmetric isotopomers of O3 disappears and so the MIF disappears, experimentally and theoretically. 

Oxygen. - IR spectroscopy was used to characterise 02 molecules trapped in vacancies in silicon crystals.607 The high-pressure Raman spectrum of 02 (to 134 GPa) shows significant Raman intensity in the metallic phase, showing that this still retains molecular character.608 High-resolution IR spectra were reported for a number of isotopomers of 03 for a variety of fundamental and overtone/combination bands.609 611... 

In 1983, Thiemens and Heisenreich reported a new isotope effect. This particular effect was unique in that the isotope ratios (e.g., of oxygen) alter on a basis other than mass. For example, in the case of ozone formation, the isotopomers... 

Xa-type halogeno molecules are listed in Table 2.2c. Table 2.2e lists vibrational frequencies of other Xa-type molecules. The O3 and ion are bent (bond angle 120-110°), and the S3, S3 , and Ss ions arc all bent (103-115°), with frequencies decreasing in this order. Detailed assignments of the IR spectra were made for six isotopomers of O3 containing and 0 in liquid oxygen solution at 77 K [454]. 

Figure 3 Separation of benzoic acid (i) isotopomers by recycie chromatography. Coiumn Cosmosii 5-Cis-P x 4.15cm x 4.6mm i.d. Mobiie phase methanoi-0.05 moi i acetate buffer (pH 4.83) 20 80 (v/v). Cycies (A) 1, (B) 5, (C) and (D) 17. (Reprinted with permission from Tanaka N, Araki M, and Kimata K (1986) Separation of oxygen isotopic compounds by reversed-phase iiquid chromatography. Journal of Chromatography 352 307-314 Eisevier.)...

Oxygen - The Raman spectrum of oxygen in argon and nitrogen matrices gave assignments to and "0"0 isotopomers. The Raman... 

Figure 14.6 compares measured and calculated isotope fractionations for all 16 possible ozone isotopomers prepared from an enriched oxygen precursor. In this figure (160160160, 160160170, 160170160, 160160180, etc. are represented as 666, 667, 676, 677, 767, 668, 686, 678, 777, 688, 868, 778, 787, 788, 878, and 888). The calculations are those of Gao and Marcus described in sections below. They are in quantitative agreement with experiment. It is interesting that isotope fractionations observed in product ozone for the totally symmetric isotopomers, 8170 = 1000 ln(777/666) and 8lsO = 1000 ln(888/666), are negative they show the heavy isotope to be depleted. Moreover, these totally symmetric effects lie on the mass dependent fractionation line [ln(777/666)]/[ln(888/666)] 0.5. That... 

Fig. 14.6 Experimental and calculated enrichments or depletions of all possible ozone iso-topomers. The labels 6, 7 and 8 represent lsO, 170, and lsO respectively. Ozone (gray bars) was produced in well scrambled oxygen mixtures at about 90 mbar and room temperature (Mauersberger et al. Adv. Atomic Mol. Opt. Phys. 50, 1 (2005)). The calculated values (vide infra) are those of Gao, Y. Q. and Marcus, R. A., J. Chem. Phys. 116, 137 (2002) setting the parameter r = 1.18 (black bars) or r = 1.0 (white bars). A typical symbol, such as 668, denotes an ozone with the isotopic composition 160160180 and consists of a mixture of symmetric (160180160) and asymmetric (160160180) isotopomers (After Gao, Y. Q. and Marcus, R. A., Science 293, 259 (2001))...

The rotational spectra of 3-methoxy-l,2,4-trioxolane (281) and 15 isotopomers containing H, and 0 point to a preferred conformation for both the ring and the methyl group and to other structural features. The C(3) atom is bonded to three oxygen atoms, for which the C—OMe bond distance is short (137.7 pm) as compared to C—(141.1 pm)... 

There can be no question that the most important species with a 3 E ground state is molecular oxygen and, not surprisingly, it was one of the first molecules to be studied in detail when microwave and millimetre-wave techniques were first developed. It was also one of the first molecules to be studied by microwave magnetic resonance, notably by Beringer and Castle [118]. In this section we concentrate on the field-free rotational spectrum, but note at the outset that this is an atypical system O2 is a homonuclear diatomic molecule in its predominant isotopomer, 160160, and as such does not possess an electric dipole moment. Spectroscopic transitions must necessarily be magnetic dipole only. 

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