PURPOSE: To measure selectively a resonance signal in a depth direction of a sample by composing an RF pulse irradiated repeatedly on the sample with plural kinds of pulses different in powers or pulse widths.
CONSTITUTION: A surface coil 3 is provided at a side surface of the sample 1, and the RF pulse is supplied to the coil 3 from an RF oscillator 4 through a gate circuit 5. A free induction damping (FID) signal obtained by the RF pulse irradiation is supplied to a CPU9 through an amplifier 6, a phase detector 7, an A/D converter 8. The CPU9 controls the RF pulse width and integrates the FID signals, and the signal is Fourier transformed to obtain a nuclear resonace spectrum. The pulse width of the pulse P1 is τ, and sequentially 2τW5τ. By setting the pulse width to various values, the signal intensity from a prescribed depth of the sample can be increased selectively. Thus, the NMR signal at the prescribed depth of the sample can be observed selectively by decreasing remarkably the influence of the signal from the other depth.
OGAWA HIDEJIROU
NAGAI SOUICHI
