Beam-foil lifetimes of n=3 levels in Fe XIII to Fe XVI II. analysis of decay curves

OSCILLATOR STRENGTHS FOR DIPOLE-ALLOWED FINE-STRUCTURE TRANSITIONS IN Fe XIII

“…The lifetime values from previous calculations are 16.4 ps [13], 16.4 ps [4] (from the LS A-value), and 16.7 ps [4] (from fine-structure components), and the value from the present calculation is 15.8 ps (as shown in Table D). The measured value is 21(4) ps with uncertainty ranging from 17 to 25 ps [7]. The calculated values agree with one another within the expected uncertainty of the various theoretical treatments, and they agree with the lower limit of the measured value, 17 ps, to within a few percent.…”

“…As the lifetime of the 3s3p 3 ( 3 S 1 o ) level of Fe XIII has been measured experimentally by Träbert et al [7], it is of considerable interest to study the decay rate from this level, namely the transition 3s 2 3p 2 (…”

“…Among the previous theoretical studies are multi-configuration Dirac-Fock calculations by Huang [2], Hartree-Fock calculations by Fawcett et al [3], Hartree-Fock calculations including relativistic effects by Bromage et al [4] and by Fawcett [5], and multi-configuration Thomas-Fermi calculations by Kastner et al [6]. The lifetime of one single level, 3s3p 3 3 S 1 o , has been measured by Träbert et al [7]. Previous works have been compiled in several National Institute of Standards and Technology (NIST) publications [8,9,10].…”

Radiative data for Fe XIII

“…The predicted lifetime is 17.0 ps, while the measured lifetime is 21 ± 4 ps (Träbert et al 1982). The other calculations under consideration yield lifetimes of 15.7 (Huang 1985), 16.8 (Fawcett 1987), 16.5 (Kohstall et al 1998) and 15.8 ps (Nahar 1999).…”

Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities: An Experimenter’s View

“…Such lifetimes are routinely measured by beam-foil spectroscopy (see [13]), but a naively obtained apparent lifetime result taken at face value may be severely misleading, if the upper level is not selectively excited, but is suffering from cascade repopulation. This problem and its treatment (by measuring the decay curves of the cascades and performing a correlated analysis, for example in the ANDC scheme [14][15][16][17], or by employing a cascade model fit) have been discussed repeatedly [17][18][19][20][21] and need not be replayed here beyond mentioning their existence (see discussion below). The 2s 2 1 S 0 -2s2p 3 P o 1 intercombination decay rate, in contrast, is several orders of magnitude smaller than the resonance decay rate and relates (for low-Z ions) to level lifetimes in the second to millisecond range.…”