| 摘要 |
FIELD: measurement equipment.SUBSTANCE: usage: for measurement of substance characteristics by NMR method. Substance: consists in the fact that to determine parameters of self-diffusion of the investigated sample they use a cycle of pulse sequence, made of the specified quantity of gradient pulses, duration, shape, amplitude and intervals between which are permanent, and two radio frequency pulses - 90-degree and 180-degree with the interval t between them, sent in the intervals between the third from the end and the last but one gradient pulse and between the last but one and the last gradient pulse, accordingly. Amplitude of the echo signal is measured at the moment of its maximum - via time t after 180-degree pulse or is produced by averaging by interval of time around this moment. To produce a diffusion drop, the cycles of measurement are repeated to change one of cycle parameters - amplitude of the gradient, duration of gradient pulses or interval between gradient pulses. The repetition period is determined by time of sample relaxation. Positive effect is achieved by setting a quasi-stationary condition in the series of gradient pulses, as a result of which the last pair of pulses in the measurement cycle of the sequence becomes close to equivalence.EFFECT: higher accuracy of diffusion drop production and determination of self-diffusion coefficient, expanded range of its measurement.8 dwg |
