Atomic Attractive Reverberation - PowerPoint PPT Presentation

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Atomic Attractive Reverberation

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  1. Nuclear Magnetic Resonance ANIMATED ILLUSTRATIONS MS Powerpoint Presentation Files Uses Animation Schemesas available in MS XP or MS 2003 versions A class room educational material File-8 FT NMR-I

  2. Computer memory Time domain DIGITIZE 15 Analogue to Digital Converter A.D.C. 11 0 Computer output FFT from FID Next Slide Frequency Domain Spectrum Computer input PULSED NMR Acquire F.I.D. Free Induction Decay NMR detection soon after a strong pulse: precessing nuclear magnetization induces a signal in coil when it is free of the perturbing EM radiation Acquisition is automatically in the digitized form F.I.D. This one-dimensional FT NMR spectrum is the same information as the C.W. NMR spectrum

  3. dimension A(50),B(50),Y(50),X(50) K=32 open (unit=1, file="output") Print 10,K DO 11 N=1,K X(N)=(N-1)*3.5/K X(N)=EXP(-1.0*X(N)) Y(N)=X(N)*(COS(2*3.14*(N-1)*10.0/K)+ 1 COS(2*3.14*(N-1)*4.0/K)) 11 write (1,20) N,Y(N) DO 12 M=1,K A(M)=0 B(M)=0 DO 13 N=1,K-1 A(M)=A(M)+Y(N)*COS(2*3.14*(M-1)*(N-1)/K) 13 B(M)=B(M)+Y(N)*SIN(2*3.14*(M-1)*(N-1)/K) A(M)=A(M)/K B(M)=B(M)/K M2=M/2 12 write (1,30) M2,A(M2),B(M2) 10 FORMAT(1x,I2) 20 FORMAT(1x,I2,2x,F10.5) 30 FORMAT(1x,I2,2x,F10.5,2x,F10.5) close (unit=1) STOP END A program in Fortran for“Fast Fourier Transform” Digitized FID Signal Digital Computer ---------------------------------------------------------------------- ---------------------- ------------ - FFT Program run OUTPUT

  4. Time domain FID data: 32 points Real Imaginary 16 data16datapoints points Frequency domainspectrum

  5. Value between +1 & 0 0 +1 F.T F.T COS Real SIN Imaginary Imaginary Real F.T Arbitrary Phase Real Imaginary t=0 Provision is made in the data processing system, for routinely applying phase corrections fc cos(2πνt) + fssin (2πνt) with fc2 +fs2 =1