Real-time detection of gaseous isotopic water molecules via photoinduced associative ionization mass spectrometry: Direct identification realized by distinctive mass spectrum patterns.

The real-time detection of gaseous HO and its typical isotopic molecules, e.g., HO, DO, HDO, and HTO, is highly desirable in many fundamental scientific studies and practical monitoring, such as mechanistic studies of HO-involved chemical reactions and radiation risk warning of abnormal HTO emissions.