The energy levels and observed spectral lines of the krypton atom, in all stages of ionization for which experimental data are available, have been compiled. Sufficient data were found to generate level and line tables for Kr I–Kr X and Kr XVIII–Kr XXXVI. For Kr XXXV and Kr XXXVI and most of Kr XXXIV theoretical values are compiled for the energy levels. In all of the other stages a few lines, some of which may be only tentative classifications, are reported. In addition for Kr I, separate tables of energy levels are tabulated for the isotopes 86Kr and 84Kr. Experimental g factors are included for Kr I and Kr II. A value, either experimental, semiempirical, or theoretical, is included for the ionization energy of each ion.

Energy Levels and Observed Spectral Lines of Krypton, Kr I through Kr XXXVI

For the first time, the evolution of luminescence from rare gases was studied as a function of number density. Synchrotron radiation served as a light source for selective and pulsed excitation of the samples. The excitation spectra confirm previous results on perturbed Rydberg states and exciton appearance in dense media. In time‐resolved emission spectra the peak energies and widths of the luminescence bands were followed. The energy separation between the fast and slow components is found to be density independent. A model proposed by Cheshnovsky et al. [Chem. Phys. Lett. 15, 475 (1972)] accounts for the change in peak width with temperature. Both lifetimes decrease with increasing density. The data extrapolate to 3.3±0.1 ns (Ar); 3.4±0.1 ns, 270±5 ns (Kr); 4.5±0.1 ns, 100±5 ns (Xe) for the low density limit. For the solid at the triple point, we obtain 1.3±0.1 ns, 82±5 ns (Kr) and 1.1±0.1 ns, 18.5±0.5 ns (Xe). Theories on density dependence of lifetimes give only a qualitative description of the exper...

Argon, krypton, and xenon excimer luminescence: From the dilute gas to the condensed phase

A review of experimental and theoretical studies of the threshold photoionization of the heavier rare-gas atoms is presented, with particular emphasis on the autoionization resonances in the spectral region between the lowest two ionization thresholds 2P3/2 and 2P1/2, accessed from the ground or excited states. Observed trends in the positions, widths and shapes of the autoionization resonances depending on the atomic number, the principal quantum number n, the orbital angular momentum quantum number l and further quantum numbers specifying the fine- and hyperfine-structure levels are summarized and discussed in the light of ab initio and multichannel quantum defect theory calculations. The dependence of the photoionization spectra on the initially prepared neutral state are also discussed, including results on the photoionization cross sections and photoelectron angular distributions of polarized excited states. The effects of various approximations in the theoretical treatment of photoionization in these systems are analysed. The very large diversity of observed phenomena and the numerous anomalies in spectral structures associated with the threshold ionization of the rare-gas atoms can be described in terms of a limited set of interactions and dynamical processes. Examples are provided illustrating characteristic aspects of the photoionization, and sets of recommended parameters describing the energy-level structure and photoionization dynamics of the rare-gas atoms are presented which were extracted in a critical analysis of the very large body of experimental and theoretical data available on these systems in the literature.

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Photoionization dynamics of excited Ne, Ar, Kr and Xe atoms near threshold

Modern approaches to the detection and imaging of rare particle interactions through gaseous and dual-phase time projection chambers are discussed. We introduce and examine their basic working principles and enabling technological assets.

Gaseous and dual-phase time projection chambers for imaging rare processes

A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.

http://iopscience.iop.org/article/10.1088/1748-0221/9/04/T04002/pdf

Modeling pulse characteristics in Xenon with NEST

Kinetics associated with the decay of the low‐lying excited states of xenon is investigated in a density range 2.5×1018 to 2.5×1020 atoms cm−3 (pressure range between 104 and 106 Pa). Three different experiments are performed, i.e., two‐photon excitation of 6p atomic states or 0+g molecular states, VUV one‐photon excitation of the 6s[3/2]1 and 6s’[1/2]1 atomic states, and laser probing of intermediate transient species. The basic experimental data are the time‐resolved second continuum excimer fluorescence at ∼173 nm and the photoionization current. It is found that all excitation decays through 6s[3/2]1 or 6s[3/2]2 with a branching ratio 9/1. Part of the 6s[3/2]1 species (70%) decay subsequently via the 6s[3/2]2 level. The effectiveness of these atomic intermediate steps is directly demonstrated by the transient laser probing. This result, the time analysis, and the discussion allow to set a clear basis to the involved processes and to rule out part of the models proposed in the literature. In particular...

Pressure effects on kinetics and decay processes in xenon after selective photoexcitation

Four even-parity atomic series corresponding to transitions from the 5s'[1/2${]}_{1}^{0}$ level to the ${(}^{2}$${\mathit{P}}_{3/2}^{0}$)np,nf levels of krypton have been observed, using a resonant multistep two-color photoionization method. The energies of 7p'[3/2${]}_{1}$, 7p'[1/2${]}_{1}$, 7p'[3/2${]}_{2}$, 7p'[1/2${]}_{0}$, np[1/2${]}_{1}$, np[3/2${]}_{2}$, np[1/2${]}_{0}$, and nf[3/2${]}_{1,2}$ levels are determined and the principal quantum numbers are calculated for n up to 45, 32, 49, and 44, respectively. Strong spectral irregularities in intensity and position are analyzed with the help of Lu-Fano diagrams and multichannel quantum defect theory in the case of the most intense 5s'[1/2${]}_{1}^{0}$\ensuremath{\rightarrow}np[1/2${]}_{0}$ series. Density shift rates have the constant value of -7.4(2)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$/${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ for the s'\ensuremath{\rightarrow}p high-n series members, outside regions where irregularities are observed, in agreement with existing doped krypton data. A close agreement with the Fermi model is obtained for these high-n members of regular series. Departure from this agreement is found for members whose excited levels are mixed with 7p' states. A clear relationship between the p\ensuremath{\sim}p' admixture and shift rate decrease, in regions of irregularities, is demonstrated.

Density effect on newly identified high-n Rydberg series of krypton by a resonantly enhanced multiphoton ionization method.

The 1P1 decay in high pressure krypton (densities 1×1020–5×1020 cm−3 ) has been investigated using selective photoexcitation. At densities above 4×1020 cm−3, the decay occurs fully through the 3P1 level. 1P1 blue or red excitation lead to identical results with evidence of a long lived reservoir effect with a rate constant associated with 1P1→3P1 transfer of ≊0.2×10−32 cm6 s−1. The kinetic scheme includes formation of short distance g symmetry excimers followed by 1g dissociation into the 3P1 state. At low density the results strongly support the hypothesis of a competing O+g(1P1) infrared excimer decay into the relaxed 1u(3P2) state.

1P1 level decay in high pressure krypton

The temperature dependence of the emissions from the 0+(3P1)and 1(3P2) Kr*Ar exciplex states in the range 85–350 K was studied using time resolved techniques, vacuum ultraviolet synchrotron radiation, and argon samples doped with minimal amounts of krypton. As the temperature is increased, the emission shifts to the blue, its width increases by almost a factor of 2, and the line shape becomes asymmetrical. The experimental line shapes have been simulated by means of Franck–Condon density calculations using the available ground state potential of Aziz and Slaman [Mol. Phys. 58, 679 (1986)] and by modeling the exciplex potentials as Morse curves. The potential parameters for the 0+ and 1 states are re=5.05±0.01 and 5.07±0.01 a0, respectively; De=1150±200 cm−1 and β=1.4±0.1 a0−1 for both states. The latter two values yield ωe=140 cm−1 and ωexe=4.3 cm−1. The energy positions of the exciplexes’s wells and their depths are compared with published results.

J.‐L. Subtil

Papers

Pressure effects on kinetics and decay processes in xenon after selective photoexcitation

Density effect on newly identified high-n Rydberg series of krypton by a resonantly enhanced multiphoton ionization method.

1P1 level decay in high pressure krypton

Exciplex vacuum ultraviolet emission spectra of KrAr: Temperature dependence and potentials