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

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- 79 - the temperature range 77-600 K, but no estimates of Debye temperatures were included. Indeed their results indicated that for all three compounds, in the temperature range 77-300 K, the temperature dependence was best described by a relationship of the form T1 = cT x where x takes the values 1.7,2.0 and 2.1 for CuI, CuBr and CuCl respectively. The results for CuCl and CuBr are a reasonable approximation to the functional form of equation (6.1) for temperatures above about 10D" However, Guenther and Hultsch's low temperature experimental Tl values for all three cuprous halides, and CuI in particular, are shorter than those reported here. This suggests a possible contribution to the measured spin-lattice relaxation times from paramagnetic impurities, perhaps an excess of copper ions as they themselves note in the case of CuI. From equation (6.1) it follows that in each of the halides the ratio. of T1 for 65Cu to that for 63Cu should be equal to (63Q/65Q)2. From pure quadrupole resonance measurements (63Q/65Q)2 is equal to 1.168 ± 0.001(82). Table 6.2 lists the ratio of T1 values for 65Cu and 63Cu as found over the temperature range of the theoretical fit to Van Kranendonk's function. The results from all three cuprous halides can be seen to be in satisfactory agreement with the theory. Over the limited temperature range of measurements on 79Br the ratio of T1 values for 81Br and 79Br was 1.35 t 0.10. The value for (79Q/81Q)2 as derived from direct measurement of th rntin of the quadrupole moments is 1.433 ± 0.002(83). The agreement between the two values is reasonable. The ratio of the measured T1 values for 63Cu and 81Br was also independent of temperature. Domngang and Wucher (80) in CuBr
- 80 - TABLE 6.2. RATIO OF TI VALUES FOR 65Cu AND 63Cu OVER TEMPERATURE RANGE OF THEORETICAL FIT TO VAN KRANENDONK'S FUNCTION SAMPLE RATIO T1Cu65/T1Cu63 CuC1 1.18 ± 0.10 CuBr 1.19 ± 0.05 CuI 1.18 ± 0.05 reported that in their pure single crystal sample the ratio of T1 values'for the copper and bromine isotopes varied. However, this variation only really became apparent at liquid nitrogen temperatures and below. The form of this behaviour was attributed to the different relative contributions to the overall spin-lattice relaxation times of optical phonons, which are not taken specific account of in the Debye model of the lattice phonon spectrum. The quadrupole moment ratios of the copper and bromine isotopes have been determined separately to a considerable degree of accuracy but there is some uncertainty in the absolute values of Q. Using the quoted values for 63Cu and 81Br respectively of -0.16 ± 0.03(84) and 0.28 ± 0.02(83) in units of 10 -28 m2 the ratio (Q/81Q2 is equal to 3.1 ± 1.6. The experimental value found over the measured temperature range was 4.0 ± 0.3, in reasonable agreement with the figure of 4.3 determined by Domngang and Wucher at the higher temperatures of their range of measurements. The theoretical and experimental ratios agree to within the large error limits imposed by the
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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
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- 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 and 104: IC 1 I. FIGURE 6.2 : Measured T1 va
Page 105: - 78 - TABLE 6.1. DEBYE TEMPERATURE
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
Page 155 and 156: - 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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