The microwave spectrum of HO2 near 65 GHz

Using a Zeeman‐modulated cavity spectrometer with a 10 sec time constant and a phase locked klystron, we have observed in the products of a discharge‐flow system, Zeeman components of the six allowed zero‐field lines at 65 070±2, 65 082±2, 65 098±2, 65 373±2, 65 397±2, and 65 401±2 MHz, and of one forbidden zero‐field line at 65 369±4 MHz. The Q of the Fabry–Perot cavity is about 10 000, and the magnetic field was swept from 0–30 G. Chemical tests indicate that the observed lines are due to HO2. They have been assigned and least‐squares fitted using a simple theoretical model to yield a value of 65 185±2 MHz for the 101–000 asymmetric rotor transition frequency of HO2, a value of −208±2 MHz for the linear combination (ebb+ecc)/2 of elements of the electron spin–molecular rotation interaction tensor, a value of −28±2 MHz for the nuclear spin–electron spin Fermi contact interaction parameter σ, and a value of +4±2 MHz for the spin–spin tensor interaction parameter λ. These constants are in excellent agreeme...