Behera Bedabyas, Das Prasanta
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore - 560012, Karnataka, India.
Department of Chemistry, Mehsana Urban Institute of Sciences, Ganpat University, Ganpat Vidyanagar, Kherva - 384012, Mehsana, Gujarat, India.
MethodsX. 2022 Sep 7;9:101847. doi: 10.1016/j.mex.2022.101847. eCollection 2022.
We have developed an infrared spectroscopic method for monitoring photochemical reactions in the gas phase. This method is based on the major components such as repetitive scan FT-IR spectrometer, multi-pass long-path gas cell, and Nd:YAG laser (ns). The FT-IR spectrometer was used as it is. The gas cell was further modified for the photolysis of the precursor. The vacuum line was designed and constructed solely in our laboratory. We make optical arrangements for both separation of fourth-harmonics (266 nm) from the fundamental (1064 nm) of Nd:YAG laser as well as to guide the UV light to the gas cell housed in the sample compartment of FT-IR. A special arrangement was done in order to get a multi-pass of UV light across the gas cell so that photolysis efficiency will increase significantly. We estimate the photolysis efficiency based on laser power, optical path-length of the laser light, vapor pressure of the precursor, and its absorption cross-section. Furthermore, we have done quantitative analysis for the precursor and photo-products using infrared absorbance and optical path length. This method is tested and validated by monitoring the photodegradation pathways of halobenzenes in the UV light.•Repetitive scan FT-IR spectrometer coupled with a multi-pass long-path gas cell and Nd:YAG laser.•Estimate photolysis efficiency of precursor and concentration of photoproducts.•Monitoring gaseous phase photochemical reactions up-to 100 of ms with spectral resolution 2 cm is possible with this system.
我们开发了一种用于监测气相光化学反应的红外光谱方法。该方法基于一些主要组件，如重复扫描傅里叶变换红外光谱仪、多程长路径气室和钕钇铝石榴石激光（纳秒级）。傅里叶变换红外光谱仪按其原样使用。气室针对前驱体的光解进行了进一步改进。真空管路是在我们实验室单独设计和构建的。我们进行了光学布置，既用于从钕钇铝石榴石激光的基频（1064纳米）中分离出四倍频（266纳米），也用于将紫外光引导至傅里叶变换红外光谱仪样品室中的气室。为了使紫外光在气室中多次通过，从而显著提高光解效率，我们做了特殊布置。我们根据激光功率、激光光路长度、前驱体的蒸气压及其吸收截面来估算光解效率。此外，我们利用红外吸光度和光路长度对前驱体和光产物进行了定量分析。该方法通过监测卤代苯在紫外光下的光降解途径进行了测试和验证。
• 重复扫描傅里叶变换红外光谱仪与多程长路径气室和钕钇铝石榴石激光联用。
• 估算前驱体的光解效率和光产物的浓度。
• 该系统能够以2厘米的光谱分辨率监测高达100毫秒的气相光化学反应。
