Question 1: 254nm light + formaldehyde + water In the absence of oxygen, ESR is used to detect the signal of hydroxyl radicals in situ. How do hydroxyl radicals are generated in absence of oxygen? Question 2: How to obtain the two values of the hyperfine coupling constants aN, aH when processing EPR data?Question 3: Whether the two values of aN and aH can directly be used for qualitative analysis of free radicals?If it is,what function does the g value have?