The (b 1Σ+) state of PH in the vacuum ultraviolet photolysis of phosphine

PH (b 1Σ+) has been observed as a primary product in the vacuum ultraviolet photolysis of PH3. The identification has been made from the analysis of some emission bands at 697.3 nm attributed to the transition PH (b 1Σ+→X 3Σ−) and from the measured energy threshold for the excitation of the above bands. The primary photolysis process PH3 (X̃ 1A1) →PH(b 1Σ+) +2H (2S) is consistent with the experimental threshold. The (b 1Σ+) state of PH and the ’’forbidden’’ transition to the ground state have been observed for the first time. The T0 value of PH (b 1Σ+) is 1.78 eV.