In an experiment to determine the pulse length, an operator observed a positive signal for pulse widths of 5 and 10 μs; as the pulse was lengthened further the intensity decreased going through a null at 20.5 μs and then becomes negative.
Explain what is happening in this experiment and use the data to determine the RF field strength in Hz and in rad s-1, and the length of a 90° pulse.
A further null in the signal was seen at 41.0 μs; to what do you attribute this?