The nitro functional group (NO₂) features strongly in compounds such as explosives, pharmaceuticals, and fragrances. However, its gas phase absorbance characteristics in the vacuum UV region (120–200 nm) have not been systematically studied. Gas chromatography/vacuum UV spectroscopy (GC/VUV) was utilized to study the gas phase VUV spectra of various nitrated compounds (e.g., nitrate esters (-R-O-NO₂), nitramines (R-N-NO₂), nitroaromatics (Ar-NO₂), and nitroalkanes (R-NO₂)). The nitro absorption maximum appeared over a wide range (170–270 nm) and its wavelength and intensity were highly dependent upon the structure of the rest of the molecule. For example, the nitroalkanes exhibited a trend in that the ratio of the relative absorption intensity between these two absorption features between the alkyl group (<150 nm) and the nitro group (200 nm) increases as the molecular weight increases. It was observed that the addition of multiple nitro functional groups on benzene or toluene resulted in an increase in intensity and blue shift from approximately 240 nm–210 nm. Nitrate esters exhibited an absorption between 170 nm and 210 nm and absorbance increased with increasing nitrogen content. The relative diversity of the spectra obtained was analyzed by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). These calculations revealed that the spectra of all the compounds analyzed could be reliably differentiated without any misclassifications.

硝基官能团 (NO ₂ ) 在炸药、药物和香料等化合物中具有很强的特征。然而，其在真空紫外区（120-200 nm）的气相吸光度特性尚未得到系统研究。气相色谱/真空紫外光谱 (GC/VUV) 用于研究各种硝化化合物（例如硝酸酯​​ (-R- O -NO ₂ )、硝胺 (RN-NO ₂ )、硝基芳烃 (Ar -NO ₂ ) 和硝基烷烃 (R-NO ₂))。硝基吸收最大值出现在很宽的范围内（170-270 nm），其波长和强度高度依赖于分子其余部分的结构。例如，硝基烷烃表现出的趋势是烷基（<150 nm）和硝基（200 nm）之间这两种吸收特征之间的相对吸收强度比随着分子量的增加而增加。观察到在苯或甲苯上添加多个硝基官能团导致强度增加和蓝移从大约 240 nm 到 210 nm。硝酸酯在 170 nm 和 210 nm 之间表现出吸收，并且吸光度随着氮含量的增加而增加。通过主成分分析 (PCA) 和线性判别分析 (LDA) 分析获得的光谱的相对多样性。这些计算表明，所有分析的化合物的光谱都可以可靠地区分，而不会出现任何错误分类。