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New spectra of some group V heteronuclear diatomics Hunt, James Edgar

Abstract

Flash photolysis of AH₃ (where A = P, As or Sb) produces metastable A atoms in the ²D° and ²P° states, AH, AH₂ and A₂. Similar transients were also observed from ACl₃ with the exception of Sb₂ from SbCl₃. The reaction forming A₂ is probably: 2AH(2ACl) + A₂ + H₂(Cl₂) Since this reaction is endothermic for SbCl no Sb₂ is observed following photolysis of SbCl₃. From the photolysis of PCl₃ a new spectrum was observed and attributed to PCI (³π ← ³Σ⁻). The bands resulting from this transition each consist of three subbands which are easily recognized since the spin-orbit splitting is less than the vibrational spacings in the ³π state. The ΔG₁/₂ value for the ³Σ⁻ ground state is significantly larger than that reported by Basco and Yee⁽¹⁶⁾ from a long wavelength spectrum assigned to PCI. This system may arise by absorption from the metastable ¹Δ state which has the same electronic configuration as the ground state. Spectra of the mixed Group V diatomics AsP, PSb and AsSb were obtained by flashing corresponding mixtures of AH₃ plus BH₃ They are formed by: AH + BH → AB + H₂ AsP was also formed from the mixture of AsCl₃ and PCl₃. That neither PSb nor AsSb were produced from the corresponding chlorides is due to the probable endothermicity for the reaction. The spectrum of AsP consists of a number of strong red degraded bands between 2030 Å and 2260 Å. Due to perturbations a vibrational analysis was not possible. A system of bands in the region of 3000 Å to 3225 Å attributed to AsP by Yee and Joness⁽²⁶⁾ was not detected. Two systems of red degraded bands are attributed to PSb. System 1 (3740 Å -3690 Å) has also been observed by Yee, Jones and Kopp⁽²⁷⁾. System 2 (2420 Å - 2640 Å) is much stronger than system 1. Again, as for AsP, strong perturbations prevented a vibrational analysis. A group of red degraded bands in the region of 3710 Å to 3525 Å were attributed to AsSb. This spectrum was also observed by Yee and Jones⁽²⁸⁾. A vibrational analysis gave ωe and ωexe values of 274.3 cm⁻¹ and 1.7 cm⁻¹ for the upper state.

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