Two-photon Decay Rates Research Articles

TWO-PHOTON TRANSITIONS IN ATOMIC INNER-SHELLS FOR Xe——RELETIVISTIC EFFECT AND ATOMIC SCREENING EFFECT

There is recent interest in atomic inner-shell two-photon decay processes because state-of-art experimental techniques (such as electronic coincident measurement etc.) have made it possible to measure the two-photon decay rate in the X-ray region. We perform relativistic self-consistent field calculations on the two-photon decay rates of (ls)-1→(ns)-1 transitions (n = 2,3,4) and (ls)-1→(nd)-1 transitions (n = 3,4) for hydrogen, hydrogen-like Xe ion and Xe atoms. Comparing the hydrogemc and the hydrogen-like Xe ion rates, we can clearly demonstrate the relativistic effect. Comparing our previous non-relativistic and our present relativistic Xe atom rates, we can also demonstrate the relativistic effect in the atomic inner-shell two photon decays. Comparing the hydrogen-like Xe ion and the Xe atom rates, we can explain the atomic screening effect. After elucidating the relativistic effect and the atomic screening effect, we are convinced that we have obtained the reliable relativistic rates, which can provide a basis to analyze th effect of electron correlations in the atomic inner-shell two-photon decays. We also compare our results with the experimental measurement and other theoretical results.

Non-relativistic self-consistent-field calculation of two-photo transitions in atomic inner shells for Xe

Recent relativistic self-consistent-field calculations of two-photon decay rates involving atomic inner shells for Xe agreed very well with the recent experimental measurements of Xe(1s)-1 to (ns)-1 and (1s)-1 to (nd)-1 transitions (n=2, 3, 4), except for the (1s)-1 to (2s)-1 decay rate which had an unexplained discrepancy of a factor of 2.9 ((1s)-1 represents an 1s hole). Moreover the measurements deviated significantly from previous existing hydrogenic and non-relativistic self-consistent-field calculations. The authors present their non-relativistic self-consistent-field calculations which also are in fair agreement with the recent experimental measurements except for the (1s)-1 to (2s)-1 decay with a discrepancy by a factor of 3.3. The non-relativistic results provide a basis to study relativistic effects for the two-photon decay processes. Further relativistic theoretical and experimental studies would be necessary in order to elucidate the discrepancy in the (1s)-1 to (2s)-1 decay.

Erratum: Spontaneous two-photon decay rates in hydrogenlike and heliumlike ions

Erratum: Spontaneous two-photon decay rates in hydrogenlike and heliumlike ions

Spontaneous two-photon decay rates in hydrogenlike and heliumlike ions.

A theoretical study of the two-photon emission rate from the 1s2s ${\mathrm{}}^{1}$S state of two-electron ions is presented. High-precision values of the nonrelativistic emission rate for ions with nuclear charge Z up to 36 are obtained by use of correlated variational wave functions of the Hylleraas type. Summations over intermediate states are performed by finite-basis-set methods. The results are used to obtain an accurate extrapolation formula and to study the convergence characteristics of a 1/Z expansion for the decay rate. The leading hydrogenic term is calculated to an accuracy which substantially exceeds Klarsfeld's, and the next term is obtained for what is believed to be the first time. Relativistic effects are taken into account by means of a screened hydrogenic approximation. The predicted decay rate for two-electron ${\mathrm{Kr}}^{34+}$ is (2.993\ifmmode\pm\else\textpm\fi{}0.012)\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, where the error is the uncertainty in the relativistic correction. This lies significantly higher than the value (2.934\ifmmode\pm\else\textpm\fi{}0.030)\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ recently measured by Marrus et al.

Is theE(1420)inJψDecay a Gluonic Bound State?

Interpretations of the $E$ meson (1420 MeV) in the radiative decay of the $\frac{J}{\ensuremath{\psi}}$ are discussed. Information on the spin and parity assignment, and the two-photon decay rate of the $E$ meson, will be sufficient for one to decide whether it is an ordinary quark-antiquark or a gluonic bound state.

Some applications of excited-state-excited-state transition densities

We derive an approximation for transition moments between excited states consistent with the approximations and assumptions normally used to obtain transition moments betwen the ground and excited states in the random-phase approximation and its higher-order approximations. We apply the result to the calculation of the photoionization cross sections of the $2^{3}S$ and $2^{1}S$ metastable states of helium by a numerical analytical continuation of the frequency-dependent polarizability. The procedure completely avoids the need for continuum basis functions. The cross sections agree well with the results of other calculations. We also predict an accurate two-photon decay rate for the $2^{1}S$ metastable state of helium. The entire procedure is immediately applicable to several problems involving photoionization of metastable states of molecules.

Two-Photon Decay Rate of the2S01Metastable State of Helium

Two alternative expressions for the two-photon decay rate of the $2^{1}S_{0}$ metastable state of helium are evaluated by performing the summations over intermediate $^{1}P_{1}$ states. The values obtained from the "length" and "velocity" expressions for the decay rate are 50.85 ${\mathrm{sec}}^{\ensuremath{-}1}$ and 50.89 ${\mathrm{sec}}^{\ensuremath{-}1}$, respectively, in good agreement with a recent experimental value and with previous calculations done by different methods. Incidental results are given for the photoionization cross sections of the $1^{1}S_{0}$ and $2^{1}S_{0}$ states of helium in the energy region 0-0.2 Ry.

Observation of muonic X-rays in helium gas and measurement of the two-photon decay rate of the 2s metastable state

We have measured the yield of theK andL lines of the muonic helium system stopping negative muons in a gaseous helium target (7 atm, 293 °K). We have also observed the two-photon decay of the ionie metastable 2s state and we found that this system is formed in (3.4 ± 0.7)% of the stopped muons.

Radiative decay of metastable hydrogenic atoms

A new highly accurate theoretical estimate of the two-photon decay rate of metastable hydrogenic atoms, viz. 1 τ = (8.2283±0.0001) Z 6 sec −1 , is obtained by performing exactly the summation over intermediate states.

Two-Photon Decay of the Singlet and Triplet Metastable States of Helium-like Ions

The two-photon decay rates and photon energy distributions of the metastable $2^{1}S$ and $2^{3}S$ states of the helium isoelectronic sequence are calculated by variational procedures for the ions He i through Ne ix.

Two-photon decay rates of the π 0 and η mesons

Two-photon decay rates of the π 0 and η mesons

Determination of the Two-Photon Decay Rate of theηMeson

Determination of the Two-Photon Decay Rate of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>η</mml:mi></mml:math>Meson