The 248 nm photolysis of phosphorus trichloride and phosphorus tribromide

• Published in: Chemical physics Vol. 183; no. 1; pp. 127 - 134
• Main Authors: Bramwell, M.J., Hughes, C., Jaeger, S.E., Whitehead, J.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.05.1994; Elsevier
• Subjects: Atomic and molecular physics; Diffuse spectra; predissociation, photodissociation; Exact sciences and technology; Molecular properties and interactions with photons; Photon interactions with molecules; Physics; Phosphorus compounds; Inorganic compounds; Fluorescence; Multi-photon processes; Excimer lasers; Photodissociation; Experimental study
• ISSN: 0301-0104
• DOI: 10.1016/0301-0104(94)00045-X

The 248 nm excimer laser photolysis of PCl 3 and PBr 3 has been studied. Emission in the region 200–600 nm is found to result from two- or three-photon processes involving short-lived (≤ 20 ns) excited species. In the case of PBr 3, emission is observed from D, D′ and E states of Br 2 formed either by direct multiphoton dissociation of PBr 3 or by 248 nm excitation of Br 2 formed by single-photon dissocation of PBr 3. The corresponding processes are energetically inaccessible for PCl 3 and no emission from molecular chlorine is observed. There are additional emission features in both photolysis systems that do not correspond to any reported states of X 2, PX or PX 2 (XCl or Br) and it is suggested that these features might be from previously unreported states of the phosphorus dihalides (PCl 2 and PBr 2). For both PCl 3 and PBr 3, we observe an excitation that is resonant with the 248 nm laser line which shows a progression with a spacing of 387±5 and 140±10 cm −1, respectively. This is attributed to 248 nm excitation of a vibrationally excited species created in a ground or low-lying electronic state by 248 nm photolysis. For PBr 3, we suggest that the pumped state could either be the A′ state of Br 2 or else the ground state of PBr 2 where the observed separation would correspond to the bending frequency, ν 2. For PCl 3, we can discount excitation of PCl 2 and there is not previously reported state of PCl or Cl 2 that can be involved.