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

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- 119 - close packed crystal lattice were calculated using the expression for the second moment M2 = 0.95B2 + 0.218J2 + 0.192J2 where B1 represents the total dipolar coupling between first near- est neighbours (including pseudo-dipolar coupling). Rotation at the magic angle removes the dipolar and pseudo-dipolar contribut- ions to the central spectrum. The second moment of the residual line is then given by M2 = 0.218J2 + 0.192J2 The width of a Gaussian lineshape is often approximated to 2,412. Applying a similar approximation here and substituting Alloul and Deltour's values for J1 and J2 of -510 Hz and -380 Hz respectively into the above expression, we obtain a theoretical linewidth of 580 Hz. The agrement with the T1 corrected value for the experimental linewidth quoted previously is very satisfactory. In view of the assumptions made in the calculation, the precise agreement may be fortuitous. Nevertheless, it does serve to demonstrate that any lifetime averaging effect on the scalar interaction room temperature is probably small. In conclusion we emphasize the preliminary nature of our measurements. The experimental accuracy could be improved by averaging the detected decay signals over a longer period of time and by employing a more reliable procedure for fitting the dead time data points. However, as the rotors at present available at
- 120 - cannot be spun at low temperatures, any determination of the scalar coupling constants in cadmium is dependent upon a detailed consid- eration of the effect of the short spin-lattice relaxation time on this interaction.
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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
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- 44 - that it apparently offered n
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- 46 - bearings suffer from instabi
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SI FIGURE 4.1 SCALE il cm : The con
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N to 9 . ýC 8 Ü7 Z w D 06 w ax U.
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- 50 - The rotors used in this work
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Ip IJýi O 1 t - 1 - 1 p OI ý I ý
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- 52 - at rotation speeds around 4
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- 53 - the manufacture of which was
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PTFE Tape_ FIGURE 4.7 rotors SCALE
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4.4.4 COMMENTS - 55 - For completen
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Clamp Pf-£-- SECTION II SECTION 11
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5.1 EQUIPMENT - 58 - CHAPTER 5 EXPE
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- 59 - the range ±1 V are digitise
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SCALE 3 cm j Cooling Gas ; tainiess
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Trensmitter EXL, FIGURE 5.3 : The s
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FIGURE $. 4 s The spectrometer prob
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Gas Tuning ransmi tter Input Receiv
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- 64 - phase can then be set so tha
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-66- The transient nuclear signals
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- 68 - 5.7.1 THE SOLID ECHO PULSE S
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- 70 - sequence may be repeated. In
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a° P/'rvu - 72 - p is the resistiv
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- 74 - combined with a low viscosit
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6.2 RESULTS AND DISCUSSION - 76 - A
Page 103 and 104: IC 1 I. FIGURE 6.2 : Measured T1 va
Page 105 and 106: - 78 - TABLE 6.1. DEBYE TEMPERATURE
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: - 118 - Lifetime broadening alone g
Page 157 and 158: - 122 - 11. L. E. Orgel, J. Phys. C
Page 159 and 160: - 124 - 59. P. J. Randall, Ph. D. T
Page 161 and 162: - 126 - 101. H. R. Khan, J. M. Reyn
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