Single-shot spatially-localized NQR using field-dependent relaxation rates
Single-shot spatially-localized NQR using field-dependent relaxation rates
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DOI：
10.1016/j.jmr.2019.106660
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发表时间：
2020-02-01
影响因子：
2.2
通讯作者：
Mandal, Soumyajit
中科院分区：
文献类型：
--
作者：
Chen, Cheng;Tang, Xinyao;Mandal, Soumyajit
核四极共振（NQR）通常用于表征含有四极核的固体材料。例如，核四极共振是一种很有前途的技术，可用于探测可塑炸药和其他违禁物质以及鉴定药品。空间分辨的NQR测量对于实现自动化样品定位、样品异质性评估和对象的化学计量认证特别感兴趣。本文提出了一种快速的“单拍”的方法，空间分辨NQR的潜力，以造福于这样的应用。所提出的方法利用的事实，即某些NQR弛豫率是场依赖性：所观察到的场依赖性是用来转换弛豫时间分布测量的静态场梯度（估计通过拉普拉斯反演的时域数据）到空间分布。采用氯酸钠和其他化合物的Cl-35和（37）Cl（）NQR对该方法进行了验证。通过使用机器学习（ML）对测量的空间分布进行分类，有效的空间分辨率也得到了提高。特别是，实验结果证明了包含氯酸钠的任意二进制分布的3D打印对象的准确的基于ML的分类。因此，此类分布可以用作基于NQR的“嵌入式条形码”，用于验证高价值物体。(C)2019爱思唯尔公司All rights reserved.
Nuclear quadrupole resonance (NQR) is commonly used to characterize solid materials containing quadrupolar nuclei. For example, NQR is a promising technique for detecting plastic explosives and other forbidden substances as well as for authenticating pharmaceutical products. Spatially-resolved NQR measurements are of particular interest for enabling automated sample positioning, evaluation of sample heterogeneity, and chemometric authentication of objects. This paper proposes a rapid "single-shot" method for spatially-resolved NQR with the potential to benefit such applications. The proposed method takes advantage of the fact that certain NQR relaxation rates are field-dependent: the observed field dependence is used to convert relaxation time distributions measured in a static field gradient (estimated via Laplace inversion of time-domain data) into spatial distributions. The method was validated using Cl-35 and (37)Cl( )NQR of sodium chlorate and other compounds. Effective spatial resolution was also improved by using machine learning (ML) to classify the measured spatial distributions. In particular, experimental results demonstrate accurate ML-based classification of 3D-printed objects containing arbitrary binary distributions of sodium chlorate. Such distributions can thus be used as NQR-based "embedded barcodes" for authenticating high-value objects. (C) 2019 Elsevier Inc. All rights reserved.