Cavity Ringdown Spectroscopy of PH₂ Radical in 465-555 nm

Absorption spectra of jet-cooled PH₂ radicals were recorded in the wavelength range of 465-555 nm using cavity ringdown spectroscopy. The PH₂ radicals were produced in a supersonic jet by pulsed direct current discharge of a mixture of PH₃ and SF₆ in argon. Seven vibronic bands with fine rotational structures have been observed and assigned as 0⁰₀、2ⁿ₀、2ⁿ₁(n=1-3) bands of the ?²A₁- Χ²B₁ electronic transition. Rotational assignments and rotational term values for each band were re-identified, and the molecular parameters including rotational constants, centrifugal distortion constants, and spin-rotation interaction constants were also improved with reasonably high precision. In addition, large perturbations observed in each quantum number of total angular momentum of the a axis level of the excited vibronic stateswere briefly discussed.