Exercises with FTNMR Simulator


Introduction

In this exercise you will use computer simulations to study the rotating frame model for NMR and then examine how the FID develops from this model. A strong understanding of this model will make it much easier to understand many other NMR experiments that we will be studying.

As you do this exercise, record your observations and comments. Take your time and think about what each step is showing. When you have completed the exercise, hand in your observations and comments.


Introduction to the FID

  1. Open the Program (FTNMR)

  2. Enter Parameters
    1. Frequency (First Nucleus, 10 Hz)
    2. Intensity (First Nucleus, 1)
    3. Done
    4. Noise (0)
    5. Flip Angle (90)
    6. T2 (10)
    7. Continue

  3. Look at the FID
    1. See how the FID Develops from the rotating frame vectors (Show FID, ShowVectors)
    2. Observe the correlation between the rotating vector and the intensity of the FID
    3. Notice when the left hand and right hand rules are used
    4. Determine the frequency of the FID and relate this to the Frequency of the Nucleus
    5. Display the Frequencies (Show Freqs)
    6. Look at the real and imaginary FID (Show FID, 0.8 sec, real or imaginary)
    7. What is the difference between the real and imaginary FID?
    8. Compare the data points to the frequency (Show Points, Points Only)

  4. How the frequency is represented in the FID
    1. Reset the Experiment (Start Over, Complete Restart)
    2. Change the Frequency to 5 Hz
    3. Done
    4. Continue
    5. Determine the frequency of the FID and relate this to the Frequency of the Nucleus
    6. Display the Frequencies (Show Freqs)
    7. Compare the data points to the frequency (Show Points, Points Only)
    8. How is the frequency of the nucleus represented in the FID?

  5. Effect of T2 relaxation on the FID
    1. Reset the Experiment (Start Over, same frequencies...)
    2. Set T2 to 1 sec
    3. What effect does this have on the FID?
    4. See how the FID Develops from the rotating frame vectors
    5. What happens in the rotating frame that explains the changes in the FID?
    6. Set T2 to 0.1 second and repeat
    7. Comment on the amount of information present in this FID, compared with the longer T2

  6. Effect of Pulse Angle on the FID
    1. Reset the Experiment
    2. Set T2 to 1 sec
    3. Change the Flip angle to 20 degrees
    4. What effect does this have on the FID?

  7. Multiple Spin Systems
    1. Reset the Experiment
    2. First Nucleus, Frequency 10 Hz, Intensity 1
    3. Second Nucleus, Frequency 5 Hz, Intensity 1
    4. 90 Degree Pulse
    5. Look at the FID, can you see the two frequency components?
    6. See how the FID Develops from the rotating frame vectors (Show FID, ShowVectors)
    7. Observe the correlation between the rotating vectors and the intensity of the FID
    8. Measure the frequency of the FID and relate this to the frequency of the nucleus
    9. Display the Frequencies (Show Freqs)


More Examples from Seminar

  1. Introduce
    1. 10 Hz, Intensity 1; T1 1, Done
    2. Noise 0; Flip Angle 90 L; Continue
    3. Show FID; All of it; Real
    4. Show FID; All of it; Imaginary
    5. Show FID; Show Vectors (note: mixing left and right hand rules).
    6. Show Points; Points Only; Fit cosine curve
    7. Cont; Don't Zero Fill; Do FT; New View; X-Range; 7 to 12 ppm
    8. Start Over; Same FID; Repeat with zero fill

  2. Apodization
    1. Start Over; Same Frequencies
    2. Add noise (0.5), 2048 data points,
    3. Continue; Do FT
    4. Start Over; Same FID
    5. Cont; Exp Smoothing; 1; Show FID; Do FT

  3. Averaging
    1. Start Over; Same Frequencies
    2. # Pulses 100; Continue; Do FT
    3. Start Over; Same FID; Continue;
    4. Exp Smoothing; Show FID; Do FT

  4. Phase
    1. Start Over; Complete Restart;
    2. Frequency 20 Hz
    3. 4096 points; noise 0; 1 pulse; Acquisition delay 0
    4. Show FID 0.8 sec; Show FID 0.08 sec
    5. Start Over; Same Frequency
    6. Acquisition delay 0.01
    7. Show FID 0.8 sec; Show Points; Fit cosine curve; Show vectors
    8. Continue; Do FT; Phase

  5. Multiple Spin System
    1. Start Over; Complete Restart
    2. 1 Hz; 2 Hz; 1024 points; T2 10 sec
    3. Show Frequencies; Show Vectors
    4. Continue; Do FT
    5. New View; X-Range; 0 ppm to 5 ppm

  6. Acquisition Parameters
    1. Start Over; Same Frequency
    2. 128 points
    3. Continue; Notice Acquisition Time; Do FT; New View; X-Range; 0 ppm to 5 ppm
    4. Start Over; Same Frequency
    5. Spectral Width 10
    6. Continue; Notice Acquisition Time; Do FT

  7. Simulate Spectrum
    1. Load 1-H spectrum of 1,2,3-trichlorobenzene
    2. Noise 0.5, 100 pulses,
    3. Show vectors
    4. zero fill, exp smooth, FT


This page is maintained by
Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

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Last Updated Monday, May 26, 1997 11:53:55.