Unusual Quartet-Doublet Phosphorescence from the Phosphaethynyl Radical, CP.

We report the first detection of phosphorescence from the phosphaethynyl radical. This rare instance of quartet-doublet emission, studied here in solid argon, is presumably promoted by efficient intersystem crossing from the originally photoexcited doublet (B 2 Σ + ) to the adjacent second quartet state, 1 4 Δ. Vibronic progressions were traced for the a 4 Σ + -X 2 Σ + and a 4 Σ + -A 2 П i systems from their origins up to (v'=0)→(v''=5) and (v'=0)→(v''=2) bands, respectively. The measured phosphorescence lifetime is 108 ± 3 ms.