Radiative processes following laser excitation of the A 2Σ+ state of PO.

Laser induced fluorescence in the (0,0) band of the A 2Σ+–X 2π system of the PO radical (∼2470 Å) has been used to study the radiative properties of the A state. A laser excitation scan of the (0,0) band and a fluorescence scan of the emission are given. Fluorescence from the B 2Σ+ state to the X state was observed (∼3250 Å) when the A state was pumped by the laser. The branching ratio for emission from the A state to the lower B and X states was indirectly determined. The A state was found to have a very short free radiative lifetime, 9.68±0.47 ns. In the absence of quenching, the excited state decay is found to be primarily due to radiative processes. Upper limits were determined for the quenching rates of Ar and He carrier gases. Relative intensities of emission of the v’=0 progression in the A–X system were also measured. These intensities were used to determine the electronic transition moment function in the region of the equilibrium internuclear distance. [ABSTRACT FROM AUTHOR]