Laser induced fluorescence of the PH2 radical

Abstract

A pulsed dye laser has been used to excite PH₂ radicals from the ²B₁ to the ²A₁ state. The radiative lifetime of the excited state is 4 ± 1 µs for v^′₂= 0–3 and decreases to 0.35 µs for v^′₂= 4. Weak, short lived fluorescence excited at higher frequencies could not be positively assigned to v^′₂= 5. The quenching rate constant for hydrogen increases steadily from 1.24 × 10¹⁰ dm³ mol^–1 s^–1 for v^′₂= 0 to ≈1.6 × 10¹¹ dm³ mol^–1 s^–1 at v^′₂= 4. Below 22 000 cm^–1 the rotational and vibrational structure corresponds to that expected on the basis of the known absorption spectrum of PH₂.