The situation for Other Nuclei.
For other nuclei, the situation is much worse. Carbon
has a resonant frequency range of 15000 Hz at typical values of Bo.
Furthermore, equations (4) and (5) imply that not all nuclei are equally
sensitive to the NMR experiment. Sensitivity is in fact proportional to
g3, and since gc = 6.73 x 107 rad T-1s-1,
this makes carbon about 62 times less sensitive than protons. Since its spin
active nucleus (13C) is only 1% abundant, the overall
receptivity (= sensitivity times isotopic abundance) is 6200 times less and
the scan width is 25 times greater than protons. To obtain a good CW type
carbon spectrum might take 600 x 25 x 6200 s = 2.95 years. For 15N, this becomes 150 years!
Return to Index page
Copyright (c) H. S. Rzepa and ICSTM Chemistry Department, 1994, 1995.