NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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- 77 - in each case so as to give the best fit to the experimental data. The same values of 6D were used for both 63 Cu and 65 Cu in each halide and also for 81 Br in the samples of cuprous bromide. From Figures 6.1 and 6.2 it can be seen that although at lower temperatures Van Kranendonk's function fits the data well, at higher temperatures the T1 values from all three halides fall progres- sively below the theoretical curves. This probably arises from a contribution to the overall spin-lattice relaxation time from increasingly rapid ionic diffusion, as has been noted elsewhere. Nevertheless the general tendency for Tl to decrease asymptotically to a T-2 behaviour at higher temperatures, but deviate from such a temperature dependence at lower temperatures is still apparent. (78'79) The values of T1 from the two specimens of cuprous bromide are in very close agreement for 63Cu, 65Cu and 81Br over the entire temperature range. The same is also true of the copper isotopes in the two cuprous iodide specimens of differing purity, showing that over the range of measurements the recorded T1 values were largely insensitive to sample purity or origin. The Debye temperatures found for each of the three cuprous halides are shown in Table 6.1. The choice of value of 8D needed to secure agreement between theory and experiment is not critical so there is an uncertainty of approximately ±25 K in the values quoted. Previous estimates of 8D as found from T1 measurements on pure single crystals of CuCl and CuBr(80) and a powdered sample of CuI(81) are included in the same table. The Debye temperatures given by Domngang and Wucher for CuCl and CuBr are in reasonable agreement with those quoted here, but there is some discrepancy in the two values for CuI. This may simply reflect the insensitivity
- 78 - TABLE 6.1. DEBYE TEMPERATURES GIV<strong>IN</strong>G BEST THEORETICAL FIT TO SAMPLE EXPERIMENTAL T, VALUES DEBYE TEMPERATURE PREVIOUS ESTIMATES 0D K 0D K CuC1 275 ± 25 300 ± 30 CuBr 275 ± 25 280 ± 20 CuI 240 ± 30 170 ± 30 of the theoretical curve to the precise choice of 8D. No other experimental estimates of the Debye temperatures in the cuprous halides could be found in the literature. Specific heat measurements will not in any case lead to identical values of 8D, because the functional dependence on the lattice dynamics is slightly different from that of the quadrupolar relaxation rate. In the Debye theory specific heats are evaluated from integral expressions of the'form T3 J6D/T p(x)x2ex x2 0 (e - 1) whereas Van Kranendonk's calculated transition probabilities are given by T3 JOD'T p2(x)ex 2x-2 0x (e 1) dx Ln(cTx/6)dx with x- by/kT and c- (6712)1/3. The functions Ln are complicated and depend upon the particular lattice type. Guenther and Hultsch(79) have reported measurements on the spin-lattice relaxation times of 63Cu in the cuprous halides over
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NNR IN RAPIDLY ROTATED METALS By R.
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I wish to express my thanks to: ACK
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quadrupole relaxation. However theo
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2.3.5 Quadrupole Relaxation 26 (i)
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5.9 Sample Preparation 71 5.9.1 Cup
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1.1 BASIC THEORY -i- CHAPTER 1 INTR
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-3- Transforming to the rotating fr
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-5- lattice and T2 is the spin-spin
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and -7- Vd(t) f(w1)cos w't dw Sao -
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-9- where the terms represent the Z
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- 11 - If rii = nrij = (Xli + X2j +
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- 13 - In powdered samples a weak i
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- 15 - This contact term manifests
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- 17 - where 0 is the angle between
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- 19 - termed pseudo-dipolar. It is
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- 21 - the non-secular terms of the
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- 23 - to the lattice directly via
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- 25 - (2.25), can then be assumed
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- 27 - quadrupole moments to produc
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- 29 - where En are the Zeeman ener
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3.1 INTRODUCTION - 31 - CHAPTER 3 N
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Aý T. B a A"T"B " - 33 - It is a g
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(-Ur Ho FIGURE 3.1. : Co-ordinate s
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D, (t) = 331 2 + 3YI2 sin 2a 4 - 36
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- 38 - X (t) = cos a cos ßp + sin
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- 40 - 3.7 THE EFFECT OF ROTATION O
Page 53 and 54: - 42 - observations are inconsisten
Page 55 and 56: - 44 - that it apparently offered n
Page 57 and 58: - 46 - bearings suffer from instabi
Page 59 and 60: SI FIGURE 4.1 SCALE il cm : The con
Page 61 and 62: N to 9 . ýC 8 Ü7 Z w D 06 w ax U.
Page 63 and 64: - 50 - The rotors used in this work
Page 65 and 66: Ip IJýi O 1 t - 1 - 1 p OI ý I ý
Page 67 and 68: - 52 - at rotation speeds around 4
Page 69 and 70: - 53 - the manufacture of which was
Page 71 and 72: PTFE Tape_ FIGURE 4.7 rotors SCALE
Page 73 and 74: 4.4.4 COMMENTS - 55 - For completen
Page 75 and 76: Clamp Pf-£-- SECTION II SECTION 11
Page 77 and 78: 5.1 EQUIPMENT - 58 - CHAPTER 5 EXPE
Page 79 and 80: - 59 - the range ±1 V are digitise
Page 81 and 82: SCALE 3 cm j Cooling Gas ; tainiess
Page 83 and 84: Trensmitter EXL, FIGURE 5.3 : The s
Page 85 and 86: FIGURE $. 4 s The spectrometer prob
Page 87 and 88: Gas Tuning ransmi tter Input Receiv
Page 89 and 90: - 64 - phase can then be set so tha
Page 91 and 92: -66- The transient nuclear signals
Page 93 and 94: - 68 - 5.7.1 THE SOLID ECHO PULSE S
Page 95 and 96: - 70 - sequence may be repeated. In
Page 97 and 98: a° P/'rvu - 72 - p is the resistiv
Page 99 and 100: - 74 - combined with a low viscosit
Page 101 and 102: 6.2 RESULTS AND DISCUSSION - 76 - A
Page 103: IC 1 I. FIGURE 6.2 : Measured T1 va
Page 107 and 108: - 80 - TABLE 6.2. RATIO OF TI VALUE
Page 109 and 110: - 82 - TABLE 6.3. DEPENDENCE OF T1
Page 111 and 112: - 84 - provides further evidence th
Page 113 and 114: - 86 - CHAPTER 7 EXPERIMENTAL RESUL
Page 115 and 116: - 88 - Lorentzian NMR lineshape of
Page 117 and 118: - 90 - at the top with epoxy glue.
Page 119 and 120: - 92 - (c) Bulk Susceptibility Effe
Page 121 and 122: - 94 - aluminium nuclei in the meta
Page 123 and 124: FIGURE 7.1 : 27A1 F. I. Ds and corr
Page 125 and 126: - 97 - TABLE 7.1. COMPUTED SECOND A
Page 127 and 128: - 99 - and Slichter(104) reported t
Page 129 and 130: - 101 - of this value would be requ
Page 131 and 132: N JL I F- 0 z J I0 0123456789 ROTAT
Page 133 and 134: -103- results obtained at a tempera
Page 135 and 136: T10 ms 3. O 2.5 2'C H 1"C o.. v 234
Page 137 and 138: 0 - 106 - CHAPTER 8 MEASUREMENTS ON
Page 139 and 140: - 108 - process for vanadium the me
Page 141 and 142: - 109 - in the same way to the prec
Page 143 and 144: Qv == , 2 28 kHz -111- which is sli
Page 145 and 146: - 113 - from Cerac Inc. (USA). The
Page 147 and 148: - 115 - 8.4.3 SPIN-LATTICE RELAXATI
Page 149 and 150: tv D Xm =o N O Ul- X- z N O FIGURE
Page 151 and 152: which gives K=0.048 an ± 0.002 - 1
Page 153 and 154: - 118 - Lifetime broadening alone g
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- 120 - cannot be spun at low tempe
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- 122 - 11. L. E. Orgel, J. Phys. C
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- 124 - 59. P. J. Randall, Ph. D. T
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- 126 - 101. H. R. Khan, J. M. Reyn
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NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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