Ultracold neutron upscattering rates in a molecular deuterium crystal
Ultracold neutron upscattering rates in a molecular deuterium crystal
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分子氘晶体中的超冷中子上散射率
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
S. Lamoreaux
中科院分区：
文献类型：
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作者：
C;A. Young;S. Lamoreaux
考虑分子内激发和声子，计算了氘分子固体中超冷中子（UCN）上散射率。不同的邻位D_{2}$（具有偶数转动量子数J）和帕拉_{2}$（具有奇数转动量子数J）具有明显不同的UCN-声子湮灭截面。此外，帕拉-到邻位-${D}_{2}$转换将UCN耦合到激发转动态的能量池中，而不需要介导声子。这种反常的上散射机制使帕拉含量为33%的正常-D {2}$固体中的UCN寿命限制在4.6msec。
A calculation of ultracold neutron (UCN) upscattering rates in molecular deuterium solids has been carried out, taking into account intramolecular excitations and phonons. The different molecular species ortho-${D}_{2}$ (with even rotational quantum number J) and para-${D}_{2}$ (with odd J) exhibit significantly different UCN-phonon annihilation cross sections. Para- to ortho-${D}_{2}$ conversion, furthermore, couples UCN to an energy bath of excited rotational states without mediating phonons. This anomalous upscattering mechanism restricts the UCN lifetime to 4.6 msec in a normal-${D}_{2}$ solid with 33% para content.