Liu Xunchen, Chae Inseok, Miriyala Naresh, Lee Dongkyu, Thundat Thomas, Kim Seonghwan
1 School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China.
2 Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada.
Appl Spectrosc. 2017 Jul;71(7):1494-1505. doi: 10.1177/0003702817693233. Epub 2017 Jan 1.
Broadband mid-infrared molecular spectroscopy is essential for detection and identification of many chemicals and materials. In this report, we present stand-off mid-infrared spectra of 1,3,5-trinitro-1,3,5-triazine or cyclotrimethylene trinitramine (RDX) residues on a stainless-steel surface measured by a broadband external cavity quantum cascade laser (QCL) system. The pulsed QCL is continuously scanned over 800 cm in the molecular fingerprint region and the amplitude of the reflection signal is measured by either a boxcar-averager-based scheme or a lock-in-amplifier-based scheme with 1 MHz and 100 kHz quartz crystal oscillators. The main background noise is due to the laser source instability and is around 0.1% of normalized intensity. The direct absorption spectra have linewidth resolution around 0.1 cm and peak height sensitivity around 10 due to baseline interference fringes. Stand-off detection of 5-50 µg/cm of RDX trace adsorbed on a stainless steel surface at the distance of 5 m is presented.
宽带中红外分子光谱对于许多化学物质和材料的检测与识别至关重要。在本报告中，我们展示了通过宽带外腔量子级联激光器（QCL）系统测量的不锈钢表面上1,3,5-三硝基-1,3,5-三嗪或环三亚甲基三硝胺（RDX）残留物的远距离中红外光谱。脉冲QCL在分子指纹区域内连续扫描800厘米，反射信号的幅度通过基于箱式平均器的方案或基于锁相放大器的方案进行测量，其中使用了1兆赫和100千赫的石英晶体振荡器。主要背景噪声源于激光源的不稳定性，约为归一化强度的0.1%。由于基线干涉条纹，直接吸收光谱的线宽分辨率约为0.1厘米，峰值高度灵敏度约为10。本文展示了在5米距离处对吸附在不锈钢表面的5-50微克/平方厘米的RDX痕量进行远距离检测的结果。
