Chlorine isotopes, separation

A similar technique has been used by Zare et al. (261, 643) for chlorine isotope separation. Isotopic mixtures of iodine monochloride (l35CI, lJ7CI) are irradiated in the presence of dibromoethylene by a laser line at 6053 A which selectively excites I37C1. An adjacent vibrational band of I35C1 is about 15 A away. The excited I37C1 reacts with added 1,2-dibromoethylene lo form the product f/wi.v-ClHC=CHCI enriched in 37C1. At this wavelength no photodissociation of ICI takes place. See p. 191. 

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

Seawater and marine pore fluids. As discussed above, the chlorine isotopic composition of modem seawater does not vary measurably. This is not surprising in light of its long residence hme (approximately 90 million years) and its conservative behavior in the water column. In contrast, marine pore fluids have been demonstrated to vary considerably. There is also the likelihood that hydrothermal fluids may be fractionated as a result of exchange with mineral phases, as phase separation under marine hydrothermal conditions does not appear to lead to measurable fractionation (e.g., Magenheim et al. 1995). However, to date no stable-chlorine isotopic compositions of marine hydrothermal fluids have been reported in the literature. 

Liebscher A, Barnes J, Sharp Z (2006) Chlorine isotope vapor-liquid fractionation during experimental fluid-phase separation at 400°C/23 Mpa to 450°C/42Mpa, Chem Geol 234 340-345 Lister GS, Kelts K, Chen KZ, Yu JQ, Niessen P (1991) Lake Qinghai, China closed-basin lake levels and the oxygen isotope record for ostracoda since the latest Pleistocene. Palaeogeogr PalaeocUmatol Palaeoecol 84 141-162... 

Figure 3.3 shows some of these possible transitions for HCI. Those with A7 = +1 are known as the R branch and occur at the high-energy side of the hypothetical transition At = 1, A7 = 0 (this is not allowed because of the selection rule, A7 = +1). Those with A7 = — 1 on the low-frequency side of the hypothetical transition form the P branch. Figure 3.4 shows the absorption spectrum of HCI at room temperature, with the rotational transitions responsible for each line. The relative intensities of the lines reflect the relative populations of the absorbing rotational levels the peaks are doublets due to the separate absorptions of the two chlorine isotopes, that is, H35C1 and H37C1, which have different reduced masses and hence values of the rotational constant B. 

Hexavalent. Uranium hexafluoride, UFe, is one of the best-studied uranium compounds in existence due to its importance for uranium isotope separation and large-scale production ( 70 000 tons per year). All of the actinide hexafluorides are extremely corrosive white (U), orange (Np), or dark brown (Pu) crystalline solids, which sublime with ease at room temperature and atmospheric pressure. The synthetic routes into the hexafluorides are given in equation (13). The volatility of the hexafluorides increases in the order Pu < Np < U in the liquid state and Pu < U < Np in the solid state. UFe is soluble in H2O, CCI4, and other chlorinated hydrocarbons, is insoluble in CS2, and decomposes in alcohols and ethers. The oxidative power of the actinide hexafluorides are in line with the transition metal hexafluorides and the order of reactivity is as follows PuFg > NpFg > UFg > MoFe > WFe. The UFe molecule can also react with metal fluorides to form UF7 and UFg. The same reactivity is not observed for the Np and Pu analogs. 

In undeuterated dioxane, Hgq and coincidentally have the same chemical shift (at the field studied), so they cannot be differentiated at low temperatures. (See Sections 1-8 and 5-2.) In l,4-dioxane- 7 (an impurity in commercial l,4-dioxane- 5 g), both and Hgq exhibit isotope shifts to a lower frequency, but H x is shifted somewhat farther. As a result, the axial and equatorial protons give separate resonances at low temperatures, in contrast to the undeuterated material. Because of a chlorine isotope effect, chloroform is a poor substance for an internal lock or a resolution standard at fields above about 9.4 T. At high resolution, the chloroform proton resonance shows up as several closely spaced peaks, due to CH( 5c1)( C1)2, CH( C1)2( C1), CH( C1)3, and CH( C1)3. 

Figure 8.11 Separation of chlorine isotopes. When the efficiency is very high isotopes of the same element can be separated which as in this example leads to two clearly defined peaks. Conditions cap Alary of 75p.m/47 cm.V = 20kV, T = 25° C, electrolyte chromate/borate pH 9.2. McDonald LT. Anal Chem. 1995, 67, 1074.

Table 2.3 shows the elements commonly found in organic compounds and the relative abnndances of their isotopes. Of these elements, only fluorine, phosphorus, and iodine are monoisotopic. Most elements are mixtures of two or more stable isotopes, differing in mass by 1 or 2 Da. Most elements include one major isotope (greater than 90 percent relative abundance), but chlorine and bromine have two rather abundant isotopes separated by 2 Da. 

Earlier proposals for fast-spectrum MSRs have used chloride salts [6]. However chloride salts have three major drawbacks (1) a need for isotopically separated chlorine to avoid high-cross-section nuclides (2) the activation product Cl, which presents significant challenges to waste management because of its mobility in the environment and (3) the more corrosive characteristics of chloride systems relative to fluoride systems. 

Even a broad laser can selectively excite one species and not the other. In the presence of a scavenger for the electronically excited ICl, such as acetylene, one can separate the two chlorine isotopes. 

In a process similar to that described in the previous item, the stored data can be used to identify not just a series of compounds but specific ones. For example, any compound containing a chlorine atom is obvious from its mass spectrum, since natural chlorine occurs as two isotopes, Cl and Cl, in a ratio of. 3 1. Thus its mass spectrum will have two molecular ions separated by two mass units (35 -i- 2 = 37) in an abundance ratio of 3 1. It becomes a trivial exercise for the computer to print out only those scans in which two ions are found separated by two mass units in the abundance ratio of 3 1 (Figure 36.10). This selection of only certain ion masses is called selected ion recording (SIR) or, sometimes, selected ion monitoring (SIM, an unfortunate... 

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