Nuclear Spin Relaxation within Interstellar Grains
Nuclear Spin Relaxation within Interstellar Grains
复制标题
星际颗粒内的核自旋弛豫
DOI：
10.1086/312137
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
B. Draine
中科院分区：
文献类型：
--
作者：
A. Lazarian;B. Draine
我们确定了一种新的机制，内部耗散的旋转动能在旋转尘埃颗粒，所产生的重新定向的核角动量，例如，质子的自旋晶粒旋转引起核自旋系统的磁化，其中核自旋的净排列平行于晶粒角速度。当颗粒不绕主轴旋转时，核磁化矢量在颗粒体坐标中进动，导致能量耗散。涉及电子自旋的类似过程是由E. M.珀塞尔和所谓的“巴内特松弛。“我们重新审视了巴内特弛豫过程的物理学，并纠正了对巴内特弛豫率的估计。我们表明，核弛豫可以是数量级更重要的巴内特松弛。这一发现意味着，“热翻转”和“热捕获”的过程是重要的晶粒尺寸范围很广。
We identify a new mechanism of internal dissipation of rotational kinetic energy in spinning dust grains, arising from the reorientation of nuclear angular momentum, e.g., spins of protons. Grain rotation induces magnetization of the nuclear spin system, with net alignment of nuclear spins parallel to the grain angular velocity. When the grain does not rotate around a principal axis, the nuclear magnetization vector precesses in grain-body coordinates, resulting in dissipation of energy. The analogous process involving electron spins was discovered by E. M. Purcell and termed "Barnett relaxation." We revisit the physics of the Barnett relaxation process and correct the estimate for the Barnett relaxation rate. We show that nuclear relaxation can be orders of magnitude more important than Barnett relaxation. This finding implies that the processes of "thermal flipping" and "thermal trapping" are important for a broad range of grain sizes.