Dear BCM 230:

In the next lecture we will finish our discussion of 2D NMR and then move on to NMR imaging. Please read pp. 81-97 of the Notes before the next lecture.

Now some summary about lecture #6:

1) The most important thing to remember about the rotating frame description of 2D NMR is the similarities between the two dimensions. Amplitude and oscillation frequency of the FID in t2 determines peak height and Larmor frequency respectively in omega2. Amplitude and oscillation frequency of the interferrogram in t1 determines peak height and frequency in omega1.

2) Similarly, the rate of decay of the FID in t2 (dependent on capital T2, the spin-spin relaxation time) determines the linewidth of the peak in omega2 while the rate of decay of the interferrogram in t1 determines the linewidth of the peak in omega1.

3) Another parallel is that the sampling rate (Nyquist frequency) in t2 determines the sweepwidth in omega2, while the sampling rate in t1 determines the sweepwidth in omega1. The sampling rate in t1 is determined by how rapidly the t1 interval (sandwiched between pulses in the evolution period of the pulse sequence, see p. 78 for example) is incremented. In the example on p.76 the t1 time is incremented in 5 msec steps. Thus 1/5 msec = 200 Hz, the sweepwidth in omega1.

4) Remembering all the parallels between the two dimensions in 2D NMR will help your understanding.

5) The next important point to remember about 2D NMR is that the design of the pulse sequence (more precisely the design of the evolution period of the pulse sequence) DETERMINES THE TYPE OF 2D SPECTRUM COLLECTED. More specifically the design of the evolution period DETERMINES THE TYPE OF INFORMATION COLLECTED DURING THE t1 INTERVAL AND THUS THE INFORMATION PRESENTED ON THE OMEGA1 AXIS OF THE 2D PLOT. (The omega2 axis is generally just chemical shift as we are accustomed to in 1D NMR from the first weeks of class).

6) Therefore by designing different pulse sequences we can obtain many different types of 2D NMR spectral information from the nuclear spin system under study. More on this topic in the next lecture.