Advanced Center of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, India; The Guo China-US Photonics Laboratory, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, China.
Laser Science & Technology Centre (LASTEC), Delhi 110054, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Nov 5;204:696-701. doi: 10.1016/j.saa.2018.06.089. Epub 2018 Jun 30.
The paper reports the temperature dependent pulsed photoacoustic spectroscopy of Dimethyl methylphosphonate (DMMP) a nerve gas simulant between 50 and 180 °C temperature range. The time domain PA spectra are recorded using two mid-IR wavelengths i.e. 3374 nm, 3495 nm of pulse duration 1.5 ns at 1 kHz repetition rate obtained from optical parametric oscillator. Two anti-symmetric stretching vibrational modes of (CHP) and (CHO) groups of DMMP molecules have very strong vibrational peaks at 2861.2 cm (3495 nm) and 2963.8 cm (3374 nm), respectively. In addition, we have also recorded the PA spectra of acetone at the vibrational frequency 3115.2 cm (3210 nm), which is the strong vibrational mode of CH band. The comparison of two PA spectra of DMMP and acetone recorded using similar PA cavity help us to understand the effect of other functional groups with respect to different excitation wavelengths. The presence of additional acoustic modes in the PA spectra of DMMP (3374 nm) above the boiling point confirms the slow process of thermal decomposition. Finally, the low level detection limit of DMMP in air is of the of the order of 0.91 ppbV.
本文报道了在 50 至 180°C 的温度范围内，作为神经毒气模拟物的二甲基甲基膦酸酯（DMMP）的温度相关脉冲光声光谱。使用光学参量振荡器获得的脉冲持续时间为 1.5ns、重复率为 1kHz 的两个中红外波长，即 3374nm 和 3495nm，记录了时域 PA 光谱。DMMP 分子的 (CHP) 和 (CHO) 基团的两个反对称伸缩振动模式在 2861.2cm（3495nm）和 2963.8cm（3374nm）处具有非常强的振动峰。此外，我们还记录了在振动频率 3115.2cm（3210nm）处的丙酮的 PA 光谱，这是 CH 带的强振动模式。使用类似的 PA 腔记录的 DMMP 和丙酮的两个 PA 光谱的比较有助于我们了解其他官能团对不同激发波长的影响。在沸点以上，DMMP 的 PA 光谱中存在额外的声波模式，这证实了热分解的缓慢过程。最后，空气中 DMMP 的低水平检测限为 0.91ppbV 左右。
