LOW-FIELD RELAXATION + STUDY OF ULTRASLOW ATOMIC MOTIONS BY MAGNETIC RESONANCE
LOW-FIELD RELAXATION + STUDY OF ULTRASLOW ATOMIC MOTIONS BY MAGNETIC RESONANCE
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DOI：
10.1103/physrev.135.a1099
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发表时间：
1964-01-01
期刊：
影响因子：
--
通讯作者：
AILION, D
中科院分区：
文献类型：
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作者：
SLICHTER, CP;AILION, D
当跳跃之间的平均时间 τ 小于 1 Δ ω 时，传统共振使人们能够通过测量线宽来研究原子的运动，其中 Δ ω 是刚性晶格线宽，或者当 τ∼ 1 ω 0 时，通过测量自旋晶格弛豫时间 T 1 ，其中 ω 0 是拉莫尔频率。我们描述了一种适用于 τ< T 1 时的新技术。因此，它适用于非常慢运动的研究。该方法类似于在 ω 0= 0 的情况下测量 T 1 。但是，通过在以拉莫尔频率旋转的参考系中进行实验，我们能够将 ω 0 保持在兆周区域。该技术的分析需要解决当所施加的静态场与局部场相当时，不频繁运动对核弛豫时间的影响问题。弛豫时间与 τ 相当，表明跳跃对于自旋来说是强烈的“碰撞”。 Bloembergen、Purcell和Pound的常规处理中没有处理强“碰撞”的情况。我们利用自旋温度和突变逼近的概念来解决这个问题。给出了实验室中弱静态场和旋转坐标系中等于或小于局部场的交变场的核弛豫的显式公式。我们同时处理扩散运动和分子重新定向。
Conventional resonance enables one to study motion of atoms by measurement of linewidth when the mean time τ between jumps is less than 1 Δ ω, where Δ ω is the rigid lattice linewidth, or by measurement of the spin-lattice relaxation time, T 1, when τ∼ 1 ω 0, where ω 0 is the Larmor frequency. We describe a new technique applicable when τ< T 1. It is therefore applicable to the study of very slow motion. The method is analogous to measuring T 1 with ω 0= 0. However, we are able to keep ω 0 in the megacycle region by performing the experiments in the reference frame rotating at the Larmor frequency. Analysis of the technique requires solution of the problem of the effect of infrequent motion on the nuclear relaxation time when the applied static field is comparable to the local field. The relaxation time is then comparable to τ, indicating that jumps are strong" collisions" for the spins. The case of strong" collisions" is not treated in the conventional treatment of Bloembergen, Purcell, and Pound. We solve the problem by use of the concept of spin temperature and the sudden approximation. Explicit formulas are given for the nuclear relaxation in the laboratory for weak static fields, and in the rotating frame for alternating fields of the order of or less than the local field. We treat both diffusional motion and molecular reorientation.