Precision lifetimes for theCa+4p2

Abstract

The mean lifetimes r of the Ca + 4p 2 Pin and 2 P\n levels have been measured to ==0.3% precision using a variant of the collinear laser-beam-ion-beam spectroscopy technique. Like previously measured precision lifetimes of light alkali-metal-like systems, these data fall significantly higher than calculations by the most recent multiconfiguration Hartree-Fock and relativistic many-body perturbation theories. Discrepancies between experiment and theory for alkali-metal-like systems have implications for the interpretation of parity-violation research.PACS numbers: 32.70.Fw, 31.30Jv, 42.55.Px, 42.62.Fi There is a current demand for precision (better than 1%) measurements of the lifetimes of electric dipole transitions of atoms or ions with a single electron outside a closed electron shell [1]. This arises from persistent attempts to improve the accuracy of relativistic many-body perturbation theory (MBPT) and multiconfiguration Dirac-Fock (MCDF) or Hartree-Fock (MCHF) calculations to this level of precision and beyond. Theoretical accuracy in transition matrix elements is required in conjunction with experimental precision (currently at the 2% level) in interference in transition amplitudes, to obtain the weak coupling constants in the analysis of atomic physics measurements [2] of parity violation in heavy, many-electron alkali-metal atoms such as Cs.During the last decade, discrepancies at the 1% level have been noted between the most precise experimental lifetimes of electric dipole decays of levels of light alkali metals, and ab initio theoretical lifetime calculations [3]. The measurements fall higher than the theory typically by > 5 standard deviations (<r) of the experimental error. In some cases, subsequent confirming measurements have been made, while different ab initio theoretical treatments tend to agree among themselves.As experimental data to further aid the evaluation of theoretical development, we report precise mean lifetime measurements on the Ap 2 Py2 and 4/7 2 P\/2 levels of Ca" 1 ". These lifetimes have recently been obtained by accurate MBPT [1], MCHF [4], and semiempirical [5] calculations. The newly measured lifetime of the 2 / > 3/2 level is r (Ca + ,4p 2^3/2) =6.924(0.019) ns while the corresponding measurement for the 2 P\/2 level is r (Ca + , 4p 2 / > i/2> =7.098(0.020) ns. Our results agree with, but are 3 times more precise than, the crossed laser-ion-beam data of Gosselin, Pinnington, and Ansbacher [6]. Our lifetime data fall higher than all of the ab initio theoretical calculations by about 2% (6a) or more, and 0.75% (2.5cr) or more higher than all semiempirical calculations. The disagreement between the theoretical and experimental results for Ca + is in accord with the earlier trend [3] for the few-electron alkali-metal-like systems, possibly signaling fundamental problems.Lifetime determinations based on laser excitation of fast beam atoms or ions are known for their accuracy and precision, since a single level is excited by the laser, and particle velocities can be well establ...

Dynamic polarizabilities for the low-lying states of Ca+

“…It not possible to reconcile the theoretical and experimental lifetimes at the 1% level. The two most recent experiments [66,67] gave lifetimes that are 2% larger than the DFCP lifetimes and 3% larger than the MBPT-SD lifetimes. Older Hanle effect experiments [68,69] gave lifetimes closer to the MBPT-SD and DFCP lifetimes.…”

Approximations for radiative cooling and heating in the solar chromosphere

“…1). The energies are from the NIST database with data coming from Sugar & Corliss (1985), the oscillator strengths are from Theodosiou (1989) with lifetimes agreeing well with the experiments of Jin & Church (1993) and the broadening parameters are from the Vienna Atomic Line Database (VALD) (Piskunov et al 1995;Kupka et al 1999). Photoionization cross-sections are from the Opacity project.…”

Atomic data from the IRON project

“…where χ i is the target ion wave function in a specific state LS i , θ i is the wave function of the free electron, Φ j are short range Ansbacher et al (1985), i Gosselin et al (1988b), j Smith & Gallagher (1966), k Rambow & Schearer (1976), l Liaw (1995), m Jin & Church (1993). Table 5.…”

“…The lifetimes τ for the 4p 2 P o and 3d 2 D levels have been measured with high precision (Jin & Church 1993;Kreuter et al 2005). Various theoretical methods have been used in trying to match these experimental values.…”