Typo correction
Of course, the hydroxyl radical is resonant in frequencies around 1665 GHz...
The standard hydroxyl maser frequency is 1.6+ GHz. There are two or three close subfrequencies around 1.6 where the radical is most active. Water itself is resonant at ~22 GHz (the cosmological "water hole"). The standard microwave oven frequency is very close to being 50% greater than 1.6+Ghz for several reasons, but commercial ovens use a closer range. Many ovens are sized so that the most prevalent frequency range ends up being lower harmonics of 2.45 GHz.
