ISSN:
1089-7690
Quelle:
AIP Digital Archive
Thema:
Physik
,
Chemie und Pharmazie
Notizen:
The vacuum ultraviolet photoionization mass spectrum of As4 is presented, from the ionization threshold to 600 A(ring). The apparent adiabatic ionization potential is ≤8.49 eV, but the true value may be significantly lower. Three broad autoionization features are observed, probably comprising members of a Rydberg series converging to the B˜ 2A1 state of As+4. The first fragment, As+3, has an appearance potential (0 K) of 11.23±0.05 eV, from which we extract ΔH0f0(As+3)≤228.7±1.3 kcal/mol. The photoion yield curve of As+2(As2) is obtained under conditions where As2 is dominant in the vapor. The adiabatic ionization potential is 9.69±0.02 eV. Two prominent autoionizing Rydberg series are observed, converging to the A 2Σ+g state of As+2, with an ionization potential of 10.238±0.002 eV. At higher energy, three members of a window resonance series can be seen, converging to the B 2Σ+u state of As+2, with an ionization potential of 15.37 eV. From an upper limit to the partial pressure of As3, equilibrium conditions, and assuming a triangular As3, we deduce ΔH0f0(As3)≥60.0 kcal/mol; other criteria suggest ΔH0f0(As3)(approximately-equal-to)63 kcal/mol. Consequently, the adiabatic ionization potential of As3 is 〈7.32 eV, and probably ≤7.19 eV. Several implications are drawn, relevant to recent studies of antimony and bismuth clusters.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.462579
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