Xe Lines Research Articles

OES diagnostics of NF3/Xe plasma for deep structures in LiNbO3

In this work, in situ non-perturbing method of optical emission spectroscopy is used to examine the features of the emission spectra of NF3/Xe plasma, which can be used for the process of continuous plasma-chemical etching of lithium niobate. To understand the physicochemical processes occurring in plasma, the influence of high-frequency power, pressure in the chamber, bias voltage and substrate temperature on the emission intensities of the F, N, Xe lines was studied. It was determined that increasing the bias voltage from -300 to -50 V and the temperature from 50 to 300°C doesn’t change the relative intensities of the analysed spectral lines, while increasing the high-frequency power from 500 to 750W and decreasing the pressure from 1.95 to 0.95Pa increase the intensities of the F, N, Xe lines.

Evidence of Extreme Ultraviolet Superfluorescence in Xenon

We present a comprehensive experimental and theoretical study on superfluorescence in the extreme ultraviolet wavelength regime. Focusing a free-electron laser pulse in a cell filled with Xe gas, the medium is quasi-instantaneously population inverted by 4d-shell ionization on the giant resonance followed by Auger decay. On the timescale of ∼10 ps to ∼100 ps (depending on parameters) a macroscopic polarization builds up in the medium, resulting in superfluorescent emission of several Xe lines in the forward direction. As the number of emitters in the system is increased by either raising the pressure or the pump-pulse energy, the emission yield grows exponentially over four orders of magnitude and reaches saturation. With increasing yield, we observe line broadening, a manifestation of superfluorescence in the spectral domain. Our novel theoretical approach, based on a full quantum treatment of the atomic system and the irradiated field, shows quantitative agreement with the experiment and supports our interpretation.

Quasimolecular emission near the Xe(5p56s 1,3P1 – 5p6 1S0) and Kr (4p55s 1,3P1 – 4p6 1S0) resonance lines induced by collisions with He atoms

This study is devoted to the theoretical investigation of the quasimolecular emission of Xe*-He and Kr*-He collision pairs near the Xe (5p56s 1,3P1 – 5p6 1S0) and Kr (4p55s 1,3P1 – 4p6 1S0) resonance atomic lines. The potential curves of the quasimolecules Xe(5p56s) + He and Kr(4p55s) + He have been obtained with the use of the effective Hamiltonian and pseudopotential methods. Based on these potential curves the processes of quasimolecular emission of Xe*+He and Kr*+He mixtures have been considered and the spectral distributions I(ħΔω) of photons emitted have been obtained in the framework of quasistatic approximation.

Detection of water molecules in inert gas based plasma by the ratios of atomic spectral lines

A new approach is considered to detect the water leaks in inert plasma-forming gas present in the reactor chamber. It is made up of the intensity ratio of Dα and Hα spectral lines in combination with O, Ar and Xe lines intensity. The concentrations of H2O, O, H and D particles have been measured with high sensitivity. At the D2 admixture pressure = 0.025 mbar, we used the acquisition time of 10 s to measure the rate of water molecules injected from the outside, Γ0 = 1.4 · 10−9 mbar · m3 · s−1, and the incoming water molecules to plasma, Γ = 5 ·10−11 mbar · m3 · s−1. The scaling proves that at small D2 admixtures (10−4 mbar), the leaks with the rates Γ0 ≈ 6 · 10−12 mbar · m3 · s−1 and Γ ≈ 2 · 10−13 mbar · m3 · s−1 can be detected and measured. The difference between Γ0 and Γ values is due to the high degree of H2O dissociation, which can be up to 97–98%.

The dynamic range of LZ

The electronics of the LZ experiment, the 7-tonne dark matter detector to be installed at the Sanford Underground Research Facility (SURF), is designed to permit studies of physics where the energies deposited range from 1 keV of nuclear-recoil energy up to 3,000 keV of electron-recoil energy. The system is designed to provide a 70% efficiency for events that produce three photoelectrons in the photomultiplier tubes (PMTs). This corresponds approximately to the lowest energy threshold achievable in multi-tonne time-projection chambers, and drives the noise specifications for the front end. The upper limit of the LZ dynamic range is defined to accommodate the electroluminescence (S2) signals. The low-energy channels of the LZ amplifiers provide the dynamic range required for the tritium and krypton calibrations. The high-energy channels provide the dynamic range required to measure the activated Xe lines.

Stellar laboratories

For the spectral analysis of spectra of hot stars with a high resolution and high signal-to-noise ratio (S/N), advanced non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that are used for their calculation. Reliable Xe VI oscillator strengths are used to identify Xe lines in the ultraviolet spectrum of the DO-type white dwarf RE0503-289 and to determine its photospheric Xe abundance. We publish newly calculated oscillator strengths that are based on a recently measured Xe VI laboratory line spectrum. These strengths were used to consider their radiative and collisional bound-bound transitions in detail in our NLTE stellar-atmosphere models to analyze Xe VI lines exhibited in high-resolution and high S/N UV observations of RE0503-289. We identify three hitherto unknown Xe VI lines in the ultraviolet spectrum of RE0503-289 and confirm the previously measured photospheric Xe abundance of this white dwarf (log Xe = -4.2 +/- 0.6). Reliable measurements and calculations of atomic data are prerequisite for stellar-atmosphere modeling. Observed Xe VI line profiles in the ultraviolet spectrum of the white dwarf RE0503-289 were well reproduced with the newly calculated Xe VI oscillator strengths.

Structural characterization of small Xe clusters using their 5s correlation satellite electron spectrum

The Xe 5s photoelectron spectrum and 5p(4)nl correlation satellites have been studied in small Xe clusters of an average size of about 15 atoms. The satellite structures are interpreted with the help of the atomic Xe lines. Transition energy shifts between the atomic and the corner/edge/face/bulk components in clusters are divided into polarization screening and exchange interaction energy. Interestingly enough, the ratios between corner/edge/face/bulk polarization screening and exchange interaction energies are found to reflect the ratios of the coordination numbers of corner/edge/face/bulk atoms in these small icosahedral cluster structures.

High-intensity xenon plasma discharge lamp for bulk-sensitive high-resolution photoemission spectroscopy

We have developed a highly brilliant xenon (Xe) discharge lamp operated by microwave-induced electron cyclotron resonance (ECR) for ultrahigh-resolution bulk-sensitive photoemission spectroscopy (PES). We observed at least eight strong radiation lines from neutral or singly ionized Xe atoms in the energy region of 8.4-10.7 eV. The photon flux of the strongest Xe I resonance line at 8.437 eV is comparable to that of the He Ialpha line (21.218 eV) from the He-ECR discharge lamp. Stable operation for more than 300 h is achieved by efficient air-cooling of a ceramic tube in the resonance cavity. The high bulk sensitivity and high-energy resolution of PES using the Xe lines are demonstrated for some typical materials.

Density and temperature sensitive features in high temperature plasma L-shell xenon emission spectra.

We present model calculations demonstrating new density and temperature sensitive ratios of groups of F- and Ne-like Xe lines which are suitable for diagnosing plasma conditions. The method is illustrated by using L-shell Xe emission to infer ${\mathit{T}}_{\mathit{e}}$ in the fuel region of indirectly driven plastic capsules filled with deuterium and doped with 0.1% Ar and 0.02% Xe. The technique uses tractable atomic models and appears scalable to other Ne-like ions.

New continuous wave infrared Ar-Xe laser at intermediate gas pressures pumped by a transverse radio frequency discharge

An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 μm. The unoptimized total output power of 330 mW was obtained for a gas mixture Ar:He:Xe=59:40:1 at a pressure of 85 Torr and a rf input power of 150 W and excitation frequency of 121 MHz.

Ionic assignment in Xe pulsed discharges by time-resolved spectral analysis

Time-resolved spectroscopy has been used in a Xe pulsed discharge. The analysis reveals a delay in the onset of emission which is characteristic of the ion, suggesting that this can be related to the time for exciting each ionization stage, for given discharge conditions. This lag is longer for higher ions. The delay determination was done characterizing it for several lines of each ion; only some are listed below. The results enable a characterization of all the nonclassified Xe lines which are known to lase in the visible and the near UV, as belonging to three different groups of ions. One has temporal lags which coincides with those of Xe iv well-classified lines; the other two, each having longer time delays, are assigned as transitions in higher ions.

Radiation-induced perturbations in CO and Xe sidelight in the CO-He-Xe laser

Laser oscillation in a sealed-off room-temperature CO-He-Xe laser was observed to perturb CO and Xe sidelight intensities in the laser discharge. Bands of the CO fourth-positive group (A 1 Pi to X 1 Sigma +) with v'=1-5 and 7 were enhanced during laser oscillation, while those with v'=6 and 8 exhibited no change in intensity. Bandheads of the CO third-positive group (b 3 Sigma +, v'=0, 1 to a 3 Pi r) were either enhanced or inhibited during laser oscillation depending on the discharge conditions; tail intensities of the third-positive bands, however, were always inhibited. Near-infrared Xe lines were enhanced (by up to 190%) during lasing. The excitation routes for the CO bands and the Xe lines have been identified, and the effects of laser oscillation on those routes are explained in terms of altered rates during lasing of electron-impact processes and collision-induced energy transfers.

Shift and oscillator strength of Xe(I) lines emitted from an alectric pulse discharge

An electric pulse discharge has been used to generate Xe plasmas with equilibrium temperatures of the order of 10 4 K and electron densities between 10 17 and 10 18 cm -3. Spectroscopic measurements were made in the range between 455 and 475 nm. The shift of the observed lines was found to vary linearly with electron density even at the highest N e values reached. Oscillator strengths were estimated for the lines at 462.4, 467.1 and 473.4 nm on the basis of a computer reconstruction of the appropriate spectral region.

Excitation of Kr and Xe in collisions with Ar +

The excitation of Kr and Xe in with Ar + ions has been studied by monitoring the resulting luminescence. Energetic collisions of Ar + with Kr and Xe excite the 116.5 and 123.6 nm Kr(I) lines and the 129.6 and 147.0 nm Xe(I) lines respectively. Apparent cross sections and kinetic energy onsets for collisional excitalition in bimolecular ion -atom collisions in the laboratory energy range of 5–100 eV are reported. The results are compared with those reported for other symmetric and asymmetric ion-atom collisions among the rare gases. Possible reaction mechanism and the criteria that may be applied to predict the relative importance of reaction pathways in ion-atom collisions are also discussed.

Experimental transition probabilities of some Xe(I) lines

Using the light absorption technique in a 132Xe afterglow plasma, we have measured the relative transition probabilities for several xenon lines which have the metastable 6 s[ 3 2 ] 2 or the resonant 6 s[ 3 2 ] 1 states as their lowest transition level. Because the transition probabilities of the 8819 Å (6 p[ 5 2 ] 3 − 6 s[ 3 2 ] 2) and 8280 Å (6 p[ 1 2 ] 0 − 6 s[ 3 2 ] 1) lines are relatively well known, we have chosen these as reference lines and have thus been able to determine the absolute values of the transition probabilities for 19 xenon lines corresponding to transitions from 6 p, 6 p′, 7 p, 8 p, 9 p, 4f and 5f to 6 s[ 3 2 ] 2, and for four lines corresponding to the transitions 6 p−6 s[ 3 2 ] 1.

Measurement of width and shift of rare gas lines emitted from a stock-tube plasma

In a diaphragm shock-tube, Ar, Kr and Xe plasmas were generated with equilibrium temperatures of 8,000 to 12,000 K. The electron densities were measured with a two-wavelength interferometer and varied from 4×10 16 to 1.4×10 17 cm -3. Emission profiles of spectral lines were recorded with a polychromator setup in 1 μs intervals using a fast data acquisition system. Width w and shift d turned out to be proportional to electron density N e for the observed lines. Stark broadening parameters w/ N e and d/ N e are presented for 3 Ar(I), 4 Kr(I) and 5 Xe(I) lines in the visible region of the spectrum.

Photoattenuation in the extreme red wings of Xe and Kr resonant lines

Photoattenuation coefficients are reported for high-pressure xenon and krypton at wavelengths in the red wings of the first resonant lines [$\mathrm{Xe}(^{3}P_{1})$, ${\ensuremath{\lambda}}_{0}=1470$ \AA{} and $\mathrm{Kr}(^{3}P_{1})$, ${\ensuremath{\lambda}}_{0}=1236$ \AA{}]. The measurements cover the range 2000-20 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ from the resonant lines. The photoattenuation spectra are interpreted in terms of Rayleigh scattering and photoabsorption by atoms, Van der Waals molecules, and unbound diatomic molecules---different portions of the spectra are dominated by different species and phenomena. Absorption by unbound diatomic molecules is interpreted via a quasistatic model of the molecule. Analysis of the data in this manner yields information concerning the structure and radiative lifetime of the lowest-bound diatomic states of $\mathrm{Xe}_{2}^{}{}_{}{}^{*}$ and $\mathrm{Kr}_{2}^{}{}_{}{}^{*}$. The significance of the results reported here in regards to dissociative noble-gas lasers (transition from a bound diatomic level to the repulsive ground level) is discussed.

Electronic states of imino radicals formed from the vacuum-ultraviolet photolysis of ethylenimine

The direct and sensitized photolyses of ehtylenimine (EI) vapor have been investigated at Kr and Xe resonance lines. The fluorescence of NH(c 1Π) or NH(A 3Π) resulting from the scission of EI is observed; EI + h ν(123.6 nm) → NH(c 1Π); EI + Kr*(3P1) → NH(c 1Π) and NH(A 3Π); EI + h ν(147.0 nm) → no emission; and EI + Xe*(3P1) → NH(A 3Π). It is suggested that the decomposition in the direct photolysis is in accordance with the spin conversation rule since NH(A 3Π) observed in the sensitized photolysis is not detected in the direct photolysis. In addition, an approximate application of the theory of unimolecular reaction to the decomposition of excited ethylene has been made in the direct photolysis of EI at Xe and Kr resonance lines indicating spin conservation in the direct photolysis, using the emiprical equation proposed by Hampson and McNesby.

Primary processes of the photolysis of ethylenimine at Xe and Kr resonance lines

The direct and sensitized photolyses of ethylenimine vapor at Kr and Xe resonance lines have been studied. The hydrocarbon products are ethylene, ethane, methane, and small amounts of acetylene, propane, and n -butane. Other products detected are hydrogen, ammonia, and the dimers of ethylenimino radicals. The effect of added oxygen or ethylene has also been investigated. Emphasis being laid on the formations of methyl radicals, ethylene, and acetylene, the quantum yields of primary processes are determined as follows; (CH2)2NH + h ν → C2H4 + NH [I], CH3 + (H2CN) [II], and C2H2 + (NH3) [III]; at Xe resonance lines φI = 0.36, φII = 0.41, φIII = 0.028; at Kr resonance lines φI = 0.22, φII = 0.13, φIII = 0.028. Xe and Kr sensitized photolyses have also been studied. A very slight difference in the product distribution between the direct and sensitized photodecompositions has been observed.

Investigation of a Xenon-plasma produced in cascaded arcs

This investigation extends earlier measurements and calculations performed on cascaded arcs burning in the noble-gases He, Ne, Ar and Kr to a Xenon discharge. Starting from intensity and line width measurements of some Xe lines, temperature and electron density profiles as well as transition probabilities are determined.E-I characteristics evaluated in conjunction with intensity profiles and temperature measurements lead to accurate results for the electrical conductivity. The pressure inside the arc chamber is variable. In a broad region of parameters LTE is established.