Electronic Resource
College Park, Md.
:
American Institute of Physics (AIP)
The Journal of Chemical Physics
90 (1989), S. 2995-3003
ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Photoion–photoelectron coincidence (PIPECO) spectra for Ar+n (n=2–4) in the wavelength region of 750–875 A(ring) have been measured at different nozzle stagnation pressures. The ionization energies (IE) for the ground Ar+2[I(1/2)u] and Ar+3[I(1/2)u] states are determined to be 14.518±0.017 eV (854±1 A(ring)) and 14.350±0.033 eV (864±2 A(ring)), in agreement with the findings of previous photoionization experiments. The IE for Ar+2[II(1/2)u] is found to be (approximately-less-than)15.83 eV (783 A(ring)). The observation of the Ar+2[II(1/2)u] PIPECO band supports the interpretation that Ar+2[II(1/2)u] is metastable with a lifetime longer than 47 μs, a value in accord with the calculated radiative lifetime of 90.9 μs for the II(1/2)u →I(1/2)g transition. The PIPECO spectrum for Ar+2 is dominated by autoionization structure similar to that resolved in the photoionization efficiency spectrum for Ar+2, indicating that a significant fraction of electrons produced by these autoionizing states are slow electrons with near-zero kinetic energies. Evidence is found that metastable Ar+3 and Ar+4 ions formed by photoionization of Ar3 and Ar4 at energies above the Ar+2[I(1/2)u]+Ar(1S0) and Ar+3[I(1/2)u]+Ar(1S0) dissociation limits may live longer than 58 and 66 μs, respectively. We suggest that the formation of Ar+3 in metastable electronic states may be responsible for the long dissociation lifetimes of Ar+3 observed in this experiment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.455901
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