hw6sol - Il;=|-‘> LAJI liaLLiJl-LI i’czx_| Figure 16...

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Unformatted text preview: Il';=| -‘:> LAJI- liaLLiJl-LI: i’czx': - ._| _..,.. Figure 16: Multipulse spin echo sequenoe. Later tau" {1r} pulse-e refocus the spins to peo- dutte additional spin ethos follow-ring on the first echo. The envelope of the decay follows and exponential in terms of T9. From reforenoe [5]. Figure 12: Two pulse sequence showing inversion recovery of M3. The FID signal produced by the sf? {Ella} pulse has an initial amplitude related to the value of M, at the end of the interval TI. Taken from referenoe i One procedure is to invert the magnetization with a lEfl degree pulse. Then the magnetic moments will relax with a time T. to the field direction. Then a 9D degree pulse (after various time delays) will rotate the spins into the sy plane so the size the magnetization can he observed [by induction in a pickup eoil}- 2a} Thelpulse width certainly has to be narrower than T. or else the spins would begin to moment in the z direction. Similarly it must be less than T101" else the spins will begin to get out of phase before they reach the xy plane. Since the width must be smaller titan these times the magnitude must be large enough to produee the 90 degree rotation in this short time. h) The delay should be much less than T1. It should be long enough for the dephasing due to the inhomogeneous fields to take place but it should also be short compared to the random spin-spin daphasing T2. i ________ _—__ gwm ., I ' | 4;) M2: @9273 EH» S; 2.2;; 153,13: i 5% i... K EH ~2~+>J= 35; (91H 42%) /-+>) _L i 9 4* pi //‘“.‘:’.:}/g“‘>‘— 1.5) ! ETJGKG> “.16.? Erfldlfifl 5.3.1.!) I j 91":- $r1+5¥ + finances. +5: 9 +5 5 5" ‘1" 21* .J'H I535- Llu. SJZ/+>:'jg 7371/?> '- "'.-.-.: .._:-.- _. -. ;- ul..n.|_.l..:-.'_.LIJ.'- ...... 5:3 IL: J.‘ |_. u L|.'. -'. _.I _-.I I—a_-N—I ._ _-. mi! .atHEL...‘ i Lfli“. 15') fflfim ital-L 43"“! , I M W :9 | £5. H 31M:er W '4 fifi‘mfiw iamfim 394'— , i ...
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hw6sol - Il;=|-‘> LAJI liaLLiJl-LI i’czx_| Figure 16...

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