Alvarez-Llamas César, Purohit Pablo, Moros Javier, Laserna Javier
UMALaserLab, Departamento de Química Analítica, Universidad de Málaga, Jiménez Fraud 4, 29010, Málaga, Spain.
UMALaserLab, Departamento de Química Analítica, Universidad de Málaga, Jiménez Fraud 4, 29010, Málaga, Spain; Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100, Copenhagen, Denmark.
Anal Chim Acta. 2022 Sep 15;1226:340261. doi: 10.1016/j.aca.2022.340261. Epub 2022 Aug 16.
The combination of data yielded by laser-induced breakdown spectroscopy (LIBS) and laser-induced plasma acoustics (LIPAc) is a topic of many prospective applications as these coexisting phenomena can cover different sample traits. Among the most interesting features that LIPAc could add to the expanded target picture is information concerning structure and geophysical characteristics elusive to LIBS. In the present work, frequency spectra of minerals were explored to discriminate between chemically similar mineralogical phases. Several replicas of four different Fe-based minerals were analyzed to identify spectral traits linked to their chemistry in the frequency domain. First, the similarity between replicas of the same mineral family was verified and then, the cosine and Euclidian distances to minerals of different species were calculated to evaluate the discrimination capabilities of frequency spectra with results being compared to those obtained by LIBS. A partial least-squares one-vs-all model is described seeking to demonstrate sample classification by frequency means exclusively. As the use of LIBS-LIPAc for in-field mineral sorting has sparked interest, experiments reported were performed in stand-off within a thermal vacuum chamber (TVC). The TVC allowed data acquisition under Earth and Mars-like conditions, with the latter serving as a test of high relevance to assess the general applicability of the conclusions reached in Earth environment. Thorough discussion of data treatment is included with a focus on the impact of interference patterns arising from the laser-induced shockwave interaction with the medium surrounding the sample to avoid non-sample related information in the data processing schemes.
激光诱导击穿光谱（LIBS）和激光诱导等离子体声学（LIPAc）产生的数据相结合是许多潜在应用的主题，因为这些共存现象可以涵盖不同的样品特征。LIPAc可以为扩展的目标图像增添的最有趣特征之一是关于LIBS难以捉摸的结构和地球物理特征的信息。在本工作中，对矿物的频谱进行了探索，以区分化学性质相似的矿物相。分析了四种不同铁基矿物的几个复制品，以识别在频域中与其化学性质相关的光谱特征。首先，验证了同一矿物家族复制品之间的相似性，然后计算了与不同物种矿物的余弦距离和欧几里得距离，以评估频谱的辨别能力，并将结果与LIBS获得的结果进行比较。描述了一种偏最小二乘一对多模型，旨在专门通过频率手段证明样品分类。由于LIBS-LIPAc用于现场矿物分选引起了人们的兴趣，因此所报道的实验是在热真空室（TVC）中进行的远距离实验。TVC允许在类似地球和火星的条件下采集数据，后者作为一个高度相关的测试，以评估在地球环境中得出的结论的普遍适用性。文中对数据处理进行了全面讨论，重点关注激光诱导冲击波与样品周围介质相互作用产生的干涉图样的影响，以避免数据处理方案中出现与样品无关的信息。
