Crystal neodymium

After removing cerium (and thorium), the nitric acid solution of rare earths is treated with ammonium nitrate. Lanthanum forms the least soluble double salt with ammonium nitrate, which may be removed from tbe solution by repeated crystallization. Neodymium is recovered from this solution as the double magnesium nitrate by continued fractionation. 

In silica, however, its fluorescence peaks at 1.088 im [15-19,21,28,29]. This anomolous fluorescence behavior for neodymium in silica is caused by its unusually low coordination number of six in a pure silica host [18,19,27]. In most glasses and crystals, neodymium coordination is seven or nine [15]. 

The term solid-state laser refers to lasers that use solids as their active medium. However, two kinds of materials are required a host crystal and an impurity dopant. The dopant is selected for its ability to form a population inversion. The Nd YAG laser, for example, uses a small number of neodymium ions as a dopant in the solid YAG (yttrium-aluminum-gar-net) crystal. Solid-state lasers are pumped with an outside source such as a flash lamp, arc lamp, or another laser. This energy is then absorbed by the dopant, raising the atoms to an excited state. Solid-state lasers are sought after because the active medium is relatively easy to handle and store. Also, because the wavelength they produce is within the transmission range of glass, they can be used with fiber optics. 

Boulon G (2004) Optical Transitions of Trivalent Neodymium and Chromium Centres in LiNb03 Crystal Host Material 107 1-25... 

These new silyl complexes are monomeric in benzene solution, but are dimeric in the solid state. The crystal structure of the samarium analogue (Figure 1) shows that dimers form via intermolecular Sm-CH3-Si interactions. The Sm-Si distance, 3.052 (8) A, is to our knowledge the longest metal-silicon distance known. As with other complexes that display Ln-CH3-Si interactions in the solid state, evidence for these interactions in solution is not observed in NMR spectra. The [H NMR chemical shifts for the neodymium... 

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

One other structure of a tricyclopentadienide has appeared (57) and it provides a further demonstration of the correlation between ionic size and coordination. Neodymium tris(methylcyclopentadienide) crystallizes as a tetramer (Fig. 10). The Nd + ion (which is slightly larger than Sm3+) is pentahapto bound to three cyclopentadienyl rings and monohapto bound to a fourth ring. This fourth ring is in turn j -bonded to another Nd + ion, until the tetramer is generated. The distances between tetramers are those expected for van der Waals contact. The crystal and molecular parameters are compared with the other tris cyclopentadienyl complexes in Table 5. 

Fig. 10. The crystal and molecular structure of tris(methylcyclopeiitadienyl)neodymium(III), from Ref. (57)...

Praesodymium may be recovered from its minerals monazite and bastana-site. The didymia extract of rare earth minerals is a mixture of praesodymia and neodymia, primarily oxides of praesodymium and neodymium. Several methods are known for isolation of rare earths. These are applicable to all rare earths including praesodymium. They include solvent extractions, ion-exchange, and fractional crystallization. While the first two methods form easy and rapid separation of rare earth metals, fractional crystaUization is more tedious. Extractions and separations of rare earths have been discussed in detail earlier (see Neodymium and Cerium). 

Figure 8.16 illustrates the energy levels of Nd in yttrium aluminium garnet (Y3AI5O12), which are involved in the laser action of this crystal (known as the neodymium YAG laser). Describe the processes that occur when the laser is working. 

Samarium-neodymium evolution diagram for lunar mare basalt 75075. Data points for the total rock, plagiodase, ilmenite, and pyroxene form a precise linear array, the slope of which gives a crystallization age of 3.70 0.07 Ga for this rock (7= 6.54 x 10 12 yr 1). The insert shows the deviations from the best-fit line in parts in 104. After Lugmair et al. (1975a). 

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. 

Varsanyi (7/2), in an interesting paper, reported the observation of some very unusual infrared fluorescence in PrCl3 Nd3+ crystals. He observed that when praseodymium chloride containing a few tenths of a per cent neodymium is illuminated with a small-filament lamp, very intense and... 

A cross-pumped chromium-neodymiunirlaser system utilizing yttrium aluminum garnet as a host was described by Ziss and Duncan (120). Again, in this crystal, as in LaA103, energy transfers from the 3d bands of chromium to the 4/levels of neodymium. 

The excitation spectrum of neodymium in the doubly doped crystal having 1 per cent chromium and 1.3 per cent neodymium clearly shows chromium bands. From a detailed study of the chromium and neodymium lifetimes, Kiss and Duncan show that energy transfer takes place from the chromium 2E state. This is contrary to the conclusion drawn by Murphy and co-workers on LaA103. 

When both neodymium and chromium are in the host together, the chromium lifetime is shortened to 3.5 msec at 77°K. The time dependence of the neodymium fluorescence is complex in the doubly doped crystal. It consists of a fast part with a lifetime of 240 /xsec and a second part with a longer time constant 3.5 msec. 

The single crystal X-ray structure of hydrated neodymium hypophosphate, NdHP206-4H20, has been determined.239 The Nd ion is eight-coordinated to four H20 and two bidentate hypophosphate anions. The details of interatomic distances and bond angles were compared with other members of this isostructural series, which extends at least from Nd to Er.240... 

Although they are not macrocyclic ligands, polyethyleneglycols behave somewhat similarly to the crown ethers regarding lanthanide complexation, as established by a number of crystal structure determinations. Thus a series of neodymium complexes shows consistent 10-coordination, namely [Nd(N03)3(tri-eg)],458 where tri-eg is triethyleneglycol, [Nd(N03)2(penta-eg)]N03,458 and [Nd(N03)2(N03)(tetra-eg)],459 where N03 is monodentate. The larger La3+ ion shows 11-coordination in [La(N03)3(tetra-eg)].460... 

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