Copper doublet

The emission from copper is shown in Figure 2.66. The two prominent lines in the copper emission are termed the copper and K., lines. The transitions responsible are to the K shell, that with principal quantum number one, the 2s and 2p levels are referred to as the L shell, etc. The Greek letters indicate from where the transition originates the 2p Is transition gives the line and the 3p-> Is the line. Sometimes the line is split into a doublet as a result of exchange terms. 

A typical nitrogen ENDOR spectrum of a copper complex (Cu(sal)2) with two magnetically equivalent 14N nuclei and with the EPR observer at mF = 0 (two sets of six ENDOR lines) is shown in Fig. 9. The pronounced splitting of the lines into a doublet structure is described by the term 4/Jai. The splitting of the more intense lines by 4/ a3 is not resolved (see B5). 

Recently similar doublet structures have been observed in other systems with inversion symmetry58,66). Fujimoto et al.58) used a somewhat different perturbation approach for the explanation of the 14N-ENDOR spectra in copper-doped a-glycine, whereas Brown and Hoffman66) determined the nitrogen ENDOR frequencies of Cu(TPP) and Ag(TPP) by numerical diagonalization of the spin Hamiltonian matrix for an electron interacting with a single pair of equivalent 14N nuclei. 

Protons have a spin 1 = and therefore often give rise to doublets. Nitrogen-14 has 1 = 1 while N has 1 = use of N can therefore simplify EPR spectra when hyperfine coupling to nitrogen is important. Both of the naturally abundant isotopes of copper have 1 =, and their magnetic moments are similar. Numerous other elements can give rise to hyperfine splitting either in naturally abundant isotopic forms or in less common isotopes after enrichment. 

Fig. 26. Computer-fitted Mossbauer spectrum for small-particle Pt-Fe alloy. Peaks (1) and (4) form the outer surface doublet. Peaks (2) and (3) form the inner doublet. Zero velocity is with respect to a 57Co in copper source. Reproduced from Bartholomew and Boudart (195) with permission.

Copper has two naturally occurring isotopes both with spin I = j. Of these, Cu is the more abundant. Selective triple resonance H- P, Cu TINDOR spectra (109) were used to study ( Cu) in [(MeO)3P]4Cu. The lines observed are split into three in an analogous way to the doublet splitting observed when / = 1, as in INDOR spectra (398) (ref. 1). 

The hardness curve and diffraction patterns of Fig. 9-3 illustrate these changes for an alpha brass, a solid solution of zinc in copper, containing 30 percent zinc by weight. The hardness remains practically constant, for an annealing period of one hour, until a temperature of 200°C is exceeded, and then decreases rapidly with increasing temperature, as shown in (a). The diffraction pattern in (b) exhibits the broad diffuse Debye lines produced by the cold-rolled, unannealed alloy. These lines become somewhat narrower for specimens annealed at 100° and 200°C, and the Ka. doublet becomes partially resolved at 250°C. At 250°, therefore, the re-... 

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