Neodymium concentration

The fluorescence lifetime, r, of Nd + in Ca3Ga2Ge30i2 crystal (a solid state laser) is measured as a function of the neodymium concentration, Cnij, giving... 

Nassau 110) has published the concentration dependence of the fluorescent lifetime of neodymium in CaW04 Nd3+ Na+. All studies were made on very high-quality laser crystals. The neodymium concentration varied from 0.1 to 5.5 atomic per cent the charge compensating sodium was held fixed at 12 atomic per cent. All data were collected at 77°K. 

Geusic et al. (118) made measurements of the fluorescent lifetime of neodymium in yttrium aluminum garnet (Y3A15012). For neodymium concentrations up to 3 atomic per cent, the measured fluorescent-decay time is approximately 200 jtxsec at both IT and 300°K. Above 6 atomic per cent, a marked decrease in the fluorescent lifetime is observed. They suggest that this is due to neodymium interactions. It is to be noted that yttrium aluminum garnet is a laser material of very exceptional quality. 

His experiments were primarily upon a single soda-lime silicate, which was chosen because it had been studied extensively in the literature and can be made in small amounts with fair optical quality. The decay for this glass with 0.8 per cent Nd203 added is shown in Fig. 33. It is quite clearly not a single exponential. One finds that the slope changes by a factor of three over the range examined and that the curvature increases with neodymium concentration. The measurements made at long times were done with a mechanical shutter that shielded the photomultiplier tube from the initial intense fluorescence. When this was not done, hysteresis in the photomultiplier tube led to spurious results. 

Figure I. The activity of the free neodymium ion as a function of total neodymium concentration in aqueous nitrate solution...

The calculated free equilibrium HDEHP dimer concentration using Equation 12 is illustrated in Table VI. The relationship of the equilibrated HDEHP dimer molar concentration with the total neodymium concentration and the total nitrate concentration in the organic phase is shown in Figures 5 and 6, respectively. 

Figure 4. Nitrate-to-neodymium concentration ratio in the organic phase as a function of the initial Nd(NOs)s concentration...

Most apatites are chlorine-rich (2-4.3%) with low F/Cl (0.1 -0.3). High fluorine ( 5%) and low chlorine (—0.25%) have been reported for apatite in spinel Iherzolites from Pacific OIB (Hauri et al., 1993). Extremely high strontium contents, commonly >2X10 ppm and up to 7 wt.% (Ionov et al., 1997 Table 9) are common in mantle apatites meaning that this phase is a major repository for strontium when present in peridotites at abundances of 0.1% or above. Rb/Sr is very low. Apatites have high levels of REE and are LREE-enriched (Table 9). Lanthanum and cerium concentrations can reach >1 wt.% and neodymium concentrations can be above 1,000 ppm. Sm/Nd is below PUM. HFSE are low and so the presence of this phase does not affect bulk rock HFSE chemistry. 

Jahn (1999) compiled samarium and neodymium concentration data for 223 analyses of eclogites and associated ultramafic rocks. Samarium concentrations range from <1 ppm to >15 ppm but most rocks contain <8 ppm (grand average = 3.1 2.5, ). Neodymium ranges from <1 ppm to 65 ppm, and most... 

Figure 15 Plots of particulate copper, vanadium, and neodymium concentrations versus particulate iron for suspended particulate material filtered in situ from the TAG hydrothermal mound, MAR, 26° N (data from German et al., 1990, 1991b). Note generally positive correlations with particulate Fe concentration for all three tracers but with additional negative (Cu) or positive (Nd) departure for sulfide-forming and scavenged elements, respectively.

Considered separately, the neodymium-isotope ratios and the neodymium concentrations have very different implications, (i) Neodymium-isotope ratios are variable in the different oceans and within an ocean they fingerprint the advective paths of water masses. This requires that the residence time of neodymium is shorter than the ocean mixing time of 10 yr (e.g., Broecker and Peng, 1982). (ii) Neodymium concentrations appear to mimic silicate, implying orders of magnitude longer residence times of 10" yr... 

In terms of the global ocean, the intermediate neodymium-isotope rahos and neodymium concentrations of the circum-Antarctic/Indian oceans are not explicable through simple mixing of North Atlantic and Pacihc source waters. In the circum-Antarctic and Indian oceans, neodymium concentrations are too low (Figure 13). This is reasonable, and could be a reflection of neodymium scavenging in the water column during advective transport between the North Atlantic and circum-Antarctic on the one hand, and the Pacihc and circum-Antarctic on the other. 

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