Nuclear Magnetic Resonance ANIMATED ILLUSTRATIONS MS Powerpoint Presentation Files Uses Animation Schemes as available in MS XP or MS 2003 versions A class room educational material File-8 FT NMR-I http://ugc-inno-nehu.com/links_from_web.html 12/28/2010 8:47:59 AM Dr.Aravamudhan

t ω = 2 π ν Fourier Transform The time domain signal forms ω ω ω ω ω ω Real Part Imaginary part ω t ω Cosine form at angular frequency ω Corresponding Exponentially Decaying function ω ω The sine function ω ω ω = 2 π ν ν is in cycles per second ω is in radians per second 12/28/2010 8:47:59 AM Dr.Aravamudhan

t AUDIO SIGNAL (FID) FROM PSD IS ANALOGUE SIGNAL WHICH IS DIGITIZED +4 8 8 +4 16 6 24 +2 29 33 4 2 31 35 -2 27 20 -3 1 12 4 t 4 8 12 16 20 24 27 29 31 33 35 Each one of the time interval of duration specified within the line with double ended arrow is the digitizer time [per[point, i.e., the Dwell Time DW. 35 values are recorded in 35 DW For DW=5 μs with 36 data points (0,1…35) Acquisition time = 36x5= 180 μs 12/28/2010 8:47:59 AM Dr.Aravamudhan

P2y P1x P2y P2y τ is fixed t1 is varied from scan to scan Z-axis Y-axis Spin system evolves freely; Magnetization vector precesses in XY plane P1x X-axis For the ‘Y’ axis π/2 pulse the component along –X axis gets to -Z direction Typical spin system manipulation by multiple pulse sequence for two dimensional experiments Precession by about 45°: can be resolved into components along X and Y axes P2y If the Spin system continues to evolve freely without any intervening pulses, Magnetization vector precesses in XY plane by angle π/2 so that the entire magnetization would be along –X axis. Thus the magnetization vector is sent to –Z direction by this pulse along Y-axis P2y Preparation Evolution t1 Mixing t ime τ Detection t2 t1 is varied from scan to scan τ is fixed acquisition 12/28/2010 8:47:59 AM Dr.Aravamudhan

Experiment with increasing t1 , the evolution time :increment 10μs How will the FT for each of this FID would look? Scan 1 3 2 3 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 8 6 4 2 1 2 4 5 6 5 2 5 4 1 4 3 3 4 5 5 DW =5μs Scan 2 3 3 2 2 4 3 2 3 2 2 1 2 4 5 6 5 3 2 4 4 3 2 2 1 4 3 2 3 3 4 4 5 5 5 4 3 Scan 3 3 3 2 2 2 1 2 4 5 6 5 4 3 2 3 4 5 5 5 4 3 2 3 3 4 4 4 3 3 2 2 2 3 1 Scan 4 3 2 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 4 5 6 5 4 3 2 3 4 5 5 5 4 3 1 Scan 5 3 3 2 2 2 3 3 3 2 2 2 6 5 1 4 3 2 3 5 3 2 3 4 4 4 4 5 5 4 3 Scan 17 2 2 1 12/28/2010 8:47:59 AM Dr.Aravamudhan

Note the variation and intensities and the initial phases of the FID FT Spectrum FID 0 μs Scan 1 Scan 2 10 μs 15 μs Scan 3 20 μs Scan 4 Note the variation and intensities and the initial phases of the FID 12/28/2010 8:47:59 AM Dr.Aravamudhan

Acquisition time Detection time t2 5 3 2 3 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 8 1 6 4 2 1 2 4 5 6 4 3 2 3 4 5 5 5 4 3 3 2 2 10 μs 4 3 2 3 2 2 1 2 4 5 6 5 3 2 2 1 4 3 2 3 4 5 5 5 4 3 2 3 3 4 4 4 15 μs 1 2 4 5 6 5 4 3 2 3 5 5 4 3 2 3 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 1 4 5 3 3 2 2 2 3 3 3 2 2 2 4 5 6 5 4 3 2 3 4 5 5 5 4 3 2 3 3 4 4 4 1 20 μs 3 3 2 2 2 6 5 3 2 3 4 3 2 3 2 2 1 3 4 5 5 4 3 2 5 3 3 4 4 4 25 μs 170 μs 2 2 1 Acquisition time Detection time t2 There are 2 time axes and FT is carried out along both time axes The signal amplitudes as a function of time for the FID are stored in the memory for each delay time defining the evolution time t1 12/28/2010 8:47:59 AM Dr.Aravamudhan

t1 Amplitude of the signal as a function of t2 for the various evolution times t1 Matrix S (t1, t2) t2 FT along t2 axis S (t1, t2) S (t1, ν2) FT along t2 axis FT along t1 axis t1 S (ν 1, ν2) FT along t1 axis ν 1 ν2 ν2 12/28/2010 8:47:59 AM Dr.Aravamudhan