Radiative decay probabilities of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level in neonlike ions

The radiative decay rates of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level in neonlike ions have been calculated for nuclear charges ranging from $Z=10$ to $Z=110$. The calculations include the magnetic dipole decay to the $(2s^{2}2p_{3/2}^{5}3s_{1/2}){}_{J=1}$ level, which is shown to be the dominant decay branch in low-$Z$ and very-high-$Z$ ions, as well as the two-electron, one-photon decays to the $(2s^{2}2p_{3/2}^{5}3p_{1/2}){}_{J=1}$ and $(2s^{2}2p_{3/2}^{5}3p_{3/2}){}_{J=1}$ levels, which dominate near $Z=50$. We also take into account a small magnetic quadrupole decay branch to the $(2s^{2}2p_{3/2}^{5}3s_{1/2}){}_{J=2}$ level and calculate the total radiative lifetime of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level. The resulting values span over 15 orders of magnitude, and much of this range is accessible with modern atomic lifetime measurement techniques. In particular, we calculate a value of $1.6\times {10}^4$ ${\mathrm{s}}^{-1}$ for the radiative decay rate of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level in Fe XVII and show that the corresponding magnetic dipole transition has a measurable spectral intensity for electron densities below about $1\times {10}^{13}$ cm${}^{-3}$.

Figure 1

Grotrian diagram of the lowest eight excited levels in neonlike iron. Levels are labeled by their ordering in the FAC calculations. In particular, levels 1–8 are $(2p_{3/2}^{5}3s_{1/2}){}_{J=2}$, $(2p_{3/2}^{5}3s_{1/2}){}_{J=1}$, $(2p_{1/2}^{5}3s_{1/2}){}_{J=0}$, $(2p_{1/2}^{5}3s_{1/2}){}_{J=1}$, $(2p_{3/2}^{5}3p_{1/2}){}_{J=1}$, $(2p_{3/2}^{5}3p_{1/2}){}_{J=2}$, $(2p_{3/2}^{5}3p_{3/2}){}_{J=3}$, and $(2p_{3/2}^{5}3p_{3/2}){}_{J=1}$, respectively. Radiative decay paths are indicated by the multipole order of the decay. Only the strongest decay paths ($>$5%) are shown; hence, only one decay path is shown if it is used more than 95% of the time. The transitions to the ground state are labeled in the notation of [2].

Figure 2

Grotrian diagram of the lowest 18 excited levels in neonlike xenon. Levels are labeled by their ordering in the FAC calculations. In particular, levels 1–6 are $(2p_{3/2}^{5}3s_{1/2}){}_{J=2}$, $(2p_{3/2}^{5}3s_{1/2}){}_{J=1}$, $(2p_{3/2}^{5}3p_{1/2}){}_{J=1}$, $(2p_{3/2}^{5}3p_{1/2}){}_{J=2}$, $(2p_{3/2}^{5}3p_{3/2}){}_{J=3}$, and $(2p_{3/2}^{5}3p_{3/2}){}_{J=1}$, respectively. Levels 16–18 are $(2p_{1/2}^{5}3s_{1/2}){}_{J=1}$, $(2p_{1/2}^{5}3s_{1/2}){}_{J=0}$, and $(2p_{3/2}^{5}3d_{5/2}){}_{J=1}$, respectively. Radiative decay paths are indicated by the multipole order of the decay. Only the strongest decay paths ($>$5%) are shown, and only one decay path is shown if it is used more than 95% of the time. The exception are the decay paths for level 17, which are to 00.1% to level 1, 27.2% to level 2, 70.6% to level 3, and 2.1% to level 6. The transitions to the ground state are labeled in the notation of [2].

Figure 3

Dependence of the level structure of neonlike ions on the nuclear charge. The four levels with a $3s$ valence electron are shown together with two levels having a $3p$ valence electron. (a) The range between $Z=10$ and $Z=110$; (b) an expanded view showing the rearrangement of levels. The level energies are calculated with FAC.

Figure 4

Separation of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=1}$ and $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ levels as a function of nuclear charge predicted by the FAC calculations. A negative value indicates that the energy of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level is higher than that of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=1}$ level.

Figure 5

Radiative decay rates of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level to various lower levels as a function of nuclear charge predicted by FAC calculations.

Figure 6

Radiative lifetime of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level as a function of nuclear charge predicted by FAC calculations.

Figure 7

Predicted spectrum of Fe xvii from an electron beam ion trap with an assumed electron-beam energy of 1200 eV and an electron density of $5\times {10}^{10}$ cm${}^{-3}$.

Figure 8

Density sensitivity of the intensity of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}\to (2s^{2}2p_{3/2}^{5}3s_{1/2}){}_{J=1}$ transition relative to that of the $(2s^{2}2p_{1/2}^{5}3d_{3/2}){}_{J=1}\to (2s^{2}2p^6){}_{J=0}$ transition.