Resonance enhanced multiphoton ionization spectroscopy of the PF radical

Abstract

PF radicals in both their ground (X 3Σ−) and metastable (a 1Δ) electronic states have been produced by the gas phase reaction of F atoms with phosphine in a discharge flow reactor and detected by mass selective resonance enhanced multiphoton ionization (REMPI) spectroscopy in the wavelength range 410–225 nm. Analysis of the longer wavelength end of this spectrum (λ≳328 nm) has enabled identification and spectroscopic characterization of five hitherto unknown Rydberg states of this radical. These we label the h 1Σ+ (T0=57 324.9 cm−1), D 3Δ (T0=58 223.0 cm−1), E 3Σ− (T0=58 690 cm−1), i 1Δ (T0=59 881.6 cm−1), and j 1Σ− (T0=61 873.9 cm−1) states, respectively. [Origins, relative to the lowest rovibrational level of the ground (X 3Σ−) state are indicated by the numbers in brackets.] Quantum defect arguments suggest that all five states derive from the electronic configuration [2Π]4pπ1. Within the shorter wavelength region we identify two additional sets of poorly resolved resonances which we associate with a further two Rydberg states belonging to series converging to the ground state ionization limit, followed by two extensive progressions of bands. Possible assignments for these two progressions are considered.