Randall E W
Department of Chemistry, Queen Mary and Westfield College, London, UK.
Solid State Nucl Magn Reson. 1997 May;8(3):179-83. doi: 10.1016/s0926-2040(97)00002-7.
A new method is presented for calibration of the pulse-length in the case that the sample, which can be either a liquid or a solid, is placed in a high field-gradient such as it experiences in the stray-, fringe-field of a solenoid. The method employs a pulse-train, with a constant phase, of the form alpha X-tau-(alpha X-tau-echo-tau-)n. This produces Hahn echoes which have variable phase in the form of phase-alternations along the echo-train. For alpha = 90 degrees the relative phase-sequence in degrees is (0, 0, 180, 180), and we may characterise this by m = 2, since there are two signals of one phase in each group. For other cases with these phase angles (0 and 180) but different numbers, m, of signals with opposite phase, we have alpha = 180/m, where m is an integer.
本文提出了一种新的方法，用于在样品（可以是液体或固体）置于高场梯度（如在螺线管的杂散场、边缘场中所经历的）的情况下校准脉冲长度。该方法采用形式为αX - τ - (αX - τ - 回波 - τ -)ⁿ的具有恒定相位的脉冲序列。这会产生哈恩回波，其相位以沿回波序列的相位交替形式变化。对于α = 90°，以度为单位的相对相位序列为(0, 0, 180, 180)，并且我们可以用m = 2来表征它，因为每组中有两个同相信号。对于具有这些相位角（0和180）但具有相反相位的不同数量m的信号的其他情况，我们有α = 180/m，其中m是整数。
