Laser photoelectron spectrometry of PO−, PH−, and PH−2

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Abstract
Fixed‐frequency laser photoelectron spectrometry has been used to study the ions PO−, PH−, and PH−2. The electron affinities of PO, PH, and PH2 were determined to be (1.092±0.010), (1.028±0.010), and (1.271±0.010) eV, respectively. A bound excited state (ã 1Δ) of PO− was observed with a term energy of (0.556±0.010) eV. The vibrational frequencies of X̃ 3Σ− PO−, ã 1Δ PO−, X̃ 2Π PH−, and 2B1 PH2 (ν1) were found to be (1000±70), (1020±80), (2230±100), and (2270±80) cm−1, respectively. A Franck–Condon factor analysis of the PO− and PH− spectra gave the equilibrium internuclear separations re(X̃ 3Σ− PO−) = (1.540±0.010) Å and 1.414⩾re(X̃ 2Π PH−) ⩾1.400 Å. The geometries of 1A1 PH−2 and 2B1 PH2 were found to be nearly the same. The PH− photoelectron spectrum includes transitions to the PH X̃ 3Σ− and ã 1Δ states, allowing determination of the intercombination separation of (0.950±0.010) eV.