Transitions In Xe Research Articles

The electron spectrum from the atomic deexcitation of

Abstract The electron spectrum from the atomic deexcitation of 131Xe following both the electron capture (EC) decay of 131Cs and the β− decay of 131I has been analyzed in the energy region from 100 eV up to 36 keV using a combined electrostatic spectrometer adjusted to the instrumental resolution varying from 4 to 20 eV. Relative intensities of the main spectrum components have been determined as follows: (LLX+MXY)/(LMM+LXY)/KLL/(KLM+KLX)/(KMM+KXY)=(1290±180)/(1650±98)/(100±5)/(46±3)/(8±2). Absolute and relative energies of the LMM+LMX, KLL, and KLM+KLX Auger transitions in Xe have also been determined as well as their relative intensities. The absolute energy of the xenon L3M4M5(1G4) Auger transition from the EC decay of 131Cs has been found to be higher by 9.4±1.1 eV than that from the β− decay of 131I. Intermediate coupling splitting of some L3MM and KLM Auger lines has been observed. Experimental data have been compared with results of calculations.

Stark widths and oscillator strengths of Xe III lines

In order to test the reliability of the Configuration Interaction (CI) method to predict the atomic parameters viz oscillator strengths of complex ions, we measured the profiles of forth (40) strong 6s-6p transitions of Xe III emitted by a pulsed capillary discharge. After deconvoluting the experimental shapes, Stark widths and relative oscillator strengths were obtained. When Least Square Fitted parameters were used in addition to extensive CI (CI + LSF), the agreement between theory and experiment for the gf's is within a factor two for the whole of the lines. Concerning the widths, the semiempirical approach provides values also within a factor two when the Gaunt factor is taken to be g(x) ~ 0.30.

K-LMandK-MMradiative Auger effect from Kr and Xe

The K-LM and K-MM radiative Auger (RA) x-ray spectra of Kr and Xe were measured. The transitions were photoinduced by an x-ray tube and measured with a high-resolution transmission curved-crystal spectrometer. For Kr the K-LM and K-MM RA yields, relative to the K${\mathrm{\ensuremath{\alpha}}}_{1,2}$ and K${\mathrm{\ensuremath{\beta}}}_{1,3}$ lines, were found to be 0.15%\ifmmode\pm\else\textpm\fi{}0.04% and 0.77%\ifmmode\pm\else\textpm\fi{}0.2%, respectively. For Xe, only an upper limit of 0.008% relative to the K${\mathrm{\ensuremath{\alpha}}}_{1,2}$ line could be deduced for the K-LM RA yield, whereas the total relative intensity of the unresolved K-${\mathit{M}}_{4,5}$${\mathit{M}}_{4,5}$ and K-${\mathit{M}}_{1}$${\mathit{N}}_{1}$ RA transitions was found to be 0.06%\ifmmode\pm\else\textpm\fi{}0.02% relative to the K${\mathrm{\ensuremath{\beta}}}_{1,3}$ line. In addition, the Xe K-${\mathit{M}}_{2,3}$${\mathit{N}}_{1}$, K-${\mathit{M}}_{1}$${\mathit{N}}_{4,5}$, and K-${\mathit{M}}_{1}$${\mathit{N}}_{2,3}$ RA transitions of Xe were also observed with a total relative intensity of 0.05%\ifmmode\pm\else\textpm\fi{}0.02%. \textcopyright{} 1996 The American Physical Society.

Continuous wetting transitions in Xe adsorbed on NaF and on plated Cs and Rb substrates.

A continuous wetting transition, long observed in model calculations but yet to be found experimentally, is predicted for Xe adsorbed on NaF as well as for Xe adsorbed on Cs and Rb substrates plated with one or more layers of a variety of other materials, including gold, copper, and silver. It is shown that, excluding plated systems, the Xe-NaF system is unique as a candidate for showing continuous wetting in a large class of systems consisting of inert liquids adsorbed on metals or insulators. Critical exponents are given.

A study of the beam-foil spectrum of Xe V

Beam-foil spectra have been searched for transitions in Xe V suggested by comparison with the structure of I IV and Cs VI, and by an MCHF calculation. Twenty-nine lines are assigned to transitions between 22 levels of the 5s25p2 and the 5s5p3, 5p5d and 5p6s configurations. Lifetime measurements for 24 of these lines are used in support of the new assignments.

Interatomic potentials for excited states of XeHe and XeAr

Interatomic potentials for the interaction of low-lying excited states of Xe(5p5nl) (nl=6s,6p,5d) with He and Ar have been calculated. A novel method has been developed that refines and extends the results of ab initio electronic structure calculations by incorporating available spectroscopic information using a model Hamiltonian. The ab initio calculations treat the heavy-atom cores using relativistic effective potentials and include spin–orbit effects at the configuration-interaction level. The model Hamiltonian depends on a small number of physically sensible parameters, some of which are extracted from the ab initio calculations, and others of which are determined more accurately from spectroscopy. The model Hamiltonian is then used to recalculate the potential curves and coupling matrix elements. The results obtained have significant implications for two classes of recent experiments. Recent measurements of rate constants for state-to-state transitions of Xe* induced by collisions with He or Ar have revealed that the magnitude of the rate depends strongly on the specific transition and collision partner. The present adiabatic potential curves exhibit several regions of strong coupling, which can be associated with the crossings of ‘‘diabatic states,’’ and which can be correlated with those transition rates found to be large. Other experiments have measured multiphoton ionization spectra of XeAr, thereby providing information on the vibrational levels of the excited-state potentials that can be compared with the present calculations.

Electron-beam-pumped laser utilizing mixtures of Xe, Kr, and Ar with two-component buffer gases

Investigations were made of high-pressure lasers emitting due to infrared transitions of Xe, Kr, and Ar atoms pumped by an electron beam of current density j = 1.7 A/cm2 and using two-component buffer gas mixtures. Energy and spectral characteristics were obtained for different active mixtures. A record energy of Q2.03 = 9 J was achieved at a wavelength of λ = 2.03 μ in an He–Ar–Xe laser, with an efficiency of η2.03 = 1.1%.

5s5p–5p^2 multiplets in Xe vii

Using beam-foil spectroscopy, we have made a detailed study of the 5s5p3P∘–5p2 3P, 5s5p3P∘–5p2 1D, and 5s5p1P∘–5p2 1D transitions in Xe vii. Discrepancies in results previously reported elsewhere have now been resolved.

Emission of Xe: N ( 2P) collision complexes near the N ( 2P→ 2D) lines

Emission of the 2P 1 2 , 3 2 → 2D 5 2 , 3 2 electric quadrupole lines of atomic nitrogen near 9606 an near-infrared spectrum of an active nitrogen afterglow using a Fourier-transform spectrometer. When Xe was added to the system, the emissions of molecular nitrogen were strongly quenched and a continuum was observed under the nitrogen atomic lines, which is attributed to emission of Xe: N ( 2P) collision complexes. The bimolecular rate constant for the collision-induced emission was derived from the ratio of the intensities of the continuum and of the discrete lines to be (3.9 ± 0.8 ) × 10 −18 cm −1s −1. The stru observed on the top of the continuum is attributed to bound—bound transitions of Xe: N ( 2P) excimers.

Electric-discharge xenon laser with weak external ionization

A laser utilizing infrared transitions in Xe, operating in the radiation field of a continuously operating nuclear reactor, was constructed and investigated for the first time. The maximum energy characteristics of the laser (specific output energy ~ 0.1 J/liter, efficiency ~ 0.1–0.2% of the energy deposited in the gas) were obtained for a mixture of the Ar:Xe = 100:1 composition at a pressure of 2 atm when the gas was ionized by 235U fission fragments. The laser could be operated at temperatures up to 650 °C.

Comparison of self-quenching streamer transitions in Xe, Kr-, and Ar-mixtures

The basic properties of the self-quenching streamer (SQS) transition have been studied for Xe and Kr mixtures, and compared with those for Ar mixtures. The transition was observed in Xe and Kr mixtures in spite of the fact that the energies of photons from Xe and Kr are insufficient to ionize directly quenching gas molecules. Since avalanche size curves measured for the SQS mode can be explained by taking into account the photoionization effect, the emission process of protons that can ionize the molecules or other more complex ionization processes should be considered to explain the transition. The complex processes could involve the emission of unknown energetic photons, interactions between the metastable states of rare gases, or multiple photoabsorption processes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

TEA laser excited by a self-sustained discharge and emitting due to infrared transitions in Xe I, Kr I, Ar I, and Ne I

Fairly intense output pulses due to infrared transitions in Xe I, Kr I, Ar I, and Ne I rare gases were generated in a simple TEA laser excited by a self-sustained discharge. Characteristics of the energy, spectral, and time parameters of this laser were studied. A specific output energy of 70 mJ liter?1 atm?1 was obtained for Xe I. It was found that the addition of Ar to a binary Ne?He mixture resulted in lasing at the 1.15 ?m wavelength in a TEA laser.

On the excitation of Xe II lines in a He-Ne-Xe hollow cathode laser

Laser oscillation at the 572.7 nm, 531.4 nm, 526.2 nm and 486.3 nm transitions of Xe II was investigated as a function of discharge parameters in a slotted hollow cathode He-Ne-Xe discharge. Problems connected to assignment of the 572.7 nm and 526.2 nm transitions are discussed and cleared. The 572.7 nm and 526.2 nm lines oscillated in a different spatial region of the discharge and showed a different dependence on He and Ne pressure, than was observed at 531.4 nm and 486.3 nm. The excitation mechanism is considered to be second kind collisions between different Ne 1s metastables and ground state Xe ions.

X-ray study of Kr and Xe adsorbed on the basal plane of nickel chloride

X-ray scattering has been used to investigate the structures and phase transitions of Xe and Kr films adsorbed on the basal plane of NiCl2. The x-ray scattering measurements were carried out both as a function of temperature at fixed coverage and as a function of coverage at fixed temperature in the monolayer and bilayer coverage regimes. The results indicate that both the monolayers of Xe and Kr adsorbed on the basal plane of NiCl2 form a 2D solid of the simple triangular structure incommensurate with the substrate and 2D melting is first order in the incommensurate solid of Xe but continuous in that of Kr. With the addition of the second-layer atoms the interparticle distance of the adsorbed atoms reduces and the crystallinity of the incommensurate solid improves.

Multiphoton ionization spectra and tunable fifth-harmonic production near five-photon resonances in Xe and Ar.

Through multiphoton ionization measurements, we have observed the interference of five-photon and internally generated fifth-harmonic excitation processes in ..delta..J = 1 even-odd parity resonant transitions in Xe and Ar. In agreement with theory, these five-photon resonances are not observable in single-pass laser beams, but are convincingly observed in counterpropagating beams. In the negatively dispersive regions of the 5d(3/2)/sup 0/J = 1 level of Xe, tunable fifth-harmonic light is generated by phase matching with various buffer-gas mixtures. The fifth-harmonic profiles are in good agreement with calculated phase-matching curves.

Feasibility of laser pumping with neutron fluxes from present-day large tokamaks

The minimum fusion-neutron flux needed to observe nuclear-pumped lasing with tokamaks can be reduced substantially by optimizing neutron scattering into the laser cell, located between adjacent toroidal-field coils. The laser lines most readily pumped are probably the 3He-Ne lines at 0.633 μm and in the infrared, where the 3He-Ne gas is excited by energetic ions produced in the 3He(n,p)T reaction. These lines are expected to lase at the levels of D-T neutron flux foreseen for the TFTR (Tokamak Fusion Test Reactor) in 1990 (≫1012 n/cm2/s), while amplification should be observable at the existing levels of D-D neutron flux (∼1010 n/cm2/s). Lasing on the 1.73 and 2.63 μm transitions of Xe may be feasible at the maximum expected levels of D-T neutron flux in TFTR enhanced by scattering.

Many-body theory of effective local potentials for electronic excitations. III. Application to giant dipole resonances.

The 4d\ensuremath{\rightarrow}f transitions in Xe and Ba and the 4p\ensuremath{\rightarrow}d transition in Kr are analyzed in terms of the effective wave functions and effective local potentials in an energy region where the response of the system is highly resonant and shows collective behavior. The effective potentials are obtained in the random-phase approximation with exchange, and the importance of relaxation is investigated. It is found that the energy dependence of the effective potential is necessary to describe the excitation spectrum reasonably well. The effects of external screening by adding and removing electrons (${\mathrm{Ba}}^{1\mathrm{\ensuremath{-}}}$-${\mathrm{Ba}}^{2+}$) are analyzed and the applicability of the atomiclike model for the 4d\ensuremath{\rightarrow}f transitions in metallic Ba is discussed.

Excitonic transitions of ordered layers of Xe on ag(111) and Al(111): A low-energy EELS study

We present the results of low-energy electron energy loss spectroscopy (EELS) studies of the lower excitonic transitions of Xe thin films on single crystal Ag(111) and Al(111) surfaces. We find that the spectra of cold (≈20 K) deposited, disordered Xe films can be interpreted in terms of broadened atomic-like transitions. However, the spectra of ordered Xe layers. obtained upon annealing, show extra transitions with no optical counterparts. These observations are explained in terms of significant dispersion and lifting of the degeneracy of levels in ordered layers of Xe. Low-energy EELS allows transitions to the split excitonic levels involving large momentum transfer.

Double beta decay, the tellurium-xenon systems and the electron associated neutrino mass

The features of double beta decay, common to many even-even nuclei are discussed in the light of a non-vanishing (Majorana) neutrino mass (matrix). The latter is considered to be the only lepton number violating effect perceptible at mass scales of a few MeV, characteristic for 2 β ± decays. Estimates of the nuclear matrix elements mediating 2β −, 2 ν and 2β −, 0 ν final states are confronted with the relative rate of the 128 Te→ 128 Xe and 130 Te→ 130 Xe transitions. It is found that the experimental rates do imply a violation of lepton number. The electron associated neutrino mass is found to be of the order of one electron volt. A conservative lower bound is m ν e ⩾ 0.8 eV, m ν e = ∑ j |U ej | 2m νj, ∑ j | ej | 2 = 1 .

Optical absorption of solid xenon at high pressure

The optical absorption of solid xenon has been studied in a diamond anvil cell up to pressures of 44 GPa in the spectral range of 2.5 to 5 eV. The onset of weak uv absorption above 36 GPa is attributed to indirect $5d$ -$5d$ interband transitions of Xe. At 44 GPa the optical gap is 3.9\ifmmode\pm\else\textpm\fi{}0.3 eV, in reasonable agreement with band-structure calculations of Ross and McMahan, but in sharp contrast to the reported metallization of Xe at 33 GPa.