NMR Sequence—Hard Pulse FID Sequence
In NMR system, RF pulse is one type of pulse which is used to generate RF magnetic field. And the RF magnetic field is the power that stimulates the sample and generates NMR signals. Therefore, different RF pulse sequences can cause different results. Hard pulse is a narrow and strong rectangle RF pulse. The frequency width of this type of pulse is wide and its main petal is large enough to cover the width of absorption frequency of the sample. So the hard pulse can excite the whole sample encircled by the RF coil. And the hard pulse sequence is usually used in relaxation analysis.
The time domain graph of the NMR FID (Free Induction Decay) sequence is displayed as Figure 1. Its parameters are listed and interpreted as follows.
NMR Hrad Pulse FID Sequence:
Fig 1 NMR hard pulse FID sequence
As can we see in the figure above, once an appropriate radio-frequency field is imposed，the magnetic vector will changed. After period of time for D3, the receiver will start to collect data. The signal which has been generated is shock in sinusoidal and decaying exponentially.
The parameters of NMR hard pulse FID sequence are listed below.
RF – the RF pulse time sequence
Rx – the receiver time sequence