Identification of structures in absorption spectrum of Kr-Xe gas mixtures close to the Xe resonance line at 146.96 nm

The origins of spectral structures that appear close to the Xe resonance line at 146.96 nm in absorption spectra of Kr gas with an admixture of Xe are discussed in this paper. It is shown that these structures can result from bound-bound and bound-free transitions in the Xe-Kr molecule between the ground state and the 1(³P₁) excited state, which both are weakly-bound. The depth of the excited state is estimated. An introduction of a hump on the 1(³P₁) state internuclear potential is suggested. Received 15 December 1999 and Received in final form 20 February 2000     

Der Zerfall des122Xe (T 1/2=20,l h) und des122J (T 1/2=3,6min)

Theγ spectra emitted in the decay of¹²²Xe and¹²²I have been investigated using Ge(Li) detectors and a Ge(Li)-NaI coincidence apparatus. 14γ transitions with energies between 61.8 and 416.9 keV have been identified in the decay of¹²²Xe, 44 transitions between 564.0 and 3,291.0 keV in the decay of¹²²I. Level schemes having 7 excited levels for¹²²I and 21 excited levels for¹²²Te are proposed.     

Lebensdauermessungen am 341,2keV-Zustand und am 404,8 keV-Zustand in131Xe

Lifetime measurements of two excited states in¹³¹Xe populated by the decay of¹³¹I have been carried out. Analysis of data, delivered from a delayed γ-γ-coincidence experiment with a Ge(Li)-Plasticdetector combination, resulted in the following values:T _1/2 of 341.2 keV level in¹³¹Xe: (2.15 ± 0.07) nsT _1/2 of 404.8 keV level in¹³¹Xe: <0.5 ns.     

The decay of127Cs

The decay of¹²⁷Cs (T _1/2=6.2 h) was investigated by means of a Ge(Li) spectrometer and a double-focusingβ-ray spectrometer. The decay scheme for¹²⁷Cs is presented including eight new levels. The spins and parities for¹²⁷Xe levels were determined. Based on the determination of the spins for the ground and first excited levels the spin 9/2 for the isomeric state of¹²⁷Xe was proposed. The relative cumulative yields of caesium isotopes from the spallation of natural cerium with 660 MeV protons are given.     

Beta-delayed proton emission from heavy nuclei: (I). The observation of coincidences between protons and γ-rays

Coincidences have been detected between γ-rays and β-delayed protons emitted after the decay of very neutron-deficient nuclei. In the three cases studied the decay proceeds to the ground state with branches to the first excited (2⁺) state of the even daughter nucleus of (58±7) % (¹¹⁵Xe to 709 keV in ¹¹⁴Te), (14±3) % (¹¹⁷Xe to 679 keV in ¹¹⁶Te), and (50±10) % (¹⁸¹Hg to 158 keV in ¹⁸⁰Pt). Upper limits of 2 and 6 % can be placed on the branches to the 4⁺ states of ¹¹⁴Te and ¹⁸⁰Pt. For the cases of ^115,117Xe, coincidences with annihilation radiation were also observed; the measured positon/proton ratio determines the difference Q—B_p, between the energy available for electron capture and the proton separation energy for the daughter. For ¹¹⁵Xe the result is 6.20±0.13 MeV, for ¹¹⁷Xe 4.10±0.20 MeV.     

Studies of vibrational relaxation in CDF3 following intense laser excitation

The V-T/R relaxation time of CDF₃ was measured studying the laser-induced infrared fluorescence emitted by vibrationally excited CDF₃. Following excitation by the 10R(12) line of a TEA CO₂ laser infrared fluorescence has been detected without spectral resolution in the 1100–700 cm^–1 range. A decay rate of 28.8 ms^–1 Torr^–1 was obtained for pure CDF₃ when it is excited with a fluence of 390 mJ/cm². Measurements have also been made in the presence of different bath gases (He, Ne, Ar, Xe, and CHF₃).     

Persistent mechanoluminescence induced by elastic deformation of ZrO2:Ti phosphors

ZrO₂:Ti phosphors show such a strong mechanoluminescence (ML) that it can be seen in day light with naked eye. When a pellet of ZrO₂:Ti phosphor mixed in epoxy resin is deformed in the elastic region at a fixed strain rate using a testing machine, ML intensity increases linearly with time, and when the deformation is stopped, ML intensity decreases exponentially with time. For a given strain rate, ML intensity increases linearly with pressure, and for a given pressure, ML intensity increases linearly with the strain rate. The total ML intensity, in the deformation region, increases quadratically with pressure; however, the total ML intensity in the post-deformation region increases linearly with pressure. ML intensity decreases with successive number of pressings, whereby the reduced ML intensity can be recovered by UV-irradiation of the sample. ML intensity increases linearly with density of filled electron traps and it is optimum for a particular concentration of Ti in ZrO₂. ML intensity should change with increasing temperature of the phosphors. Although ZrO₂ is non-piezoelectric as a whole, it seems that the local structures near the Ti ions in ZrO₂ crystals are in the piezoelectric phase. The elastico ML in ZrO₂ phosphors can be understood on the basis of the localized piezoelectrification-induced detrapping model. According to this model, the localized piezoelectric field near Ti ions causes detrapping of electrons and subsequently the detrapped electrons moving in the conduction band are captured by the energy state of excited Ti⁴⁺ ions, whereby excited Ti⁴⁺ ions are produced and consequently the decay of excited Ti⁴⁺ ions gives rise to the light emission. The expressions derived on the basis of this model are able to explain satisfactorily the characteristics of ML. The relaxation time of localized piezoelectric charges and the threshold pressure for the ML emission can be determined from ML measurements. The long decay of elastico ML indicates the possibility of exploring persistent elastico ML, which may be useful for the fabrication of dim light sources capable of operating without any external power.     

Radiative and non-radiative decays from the excited state of Ti3+ ions in oxide crystals

The fluorescence spectra of Ti³⁺ in Y₃Al₅O₁₂ (YAG), Al₂O₃ (sapphire), YAlO₃ (YAP) observed at 10 K are composed of zero-phonon lines accompanied by the broad vibronic sidebands. The temperature dependence of the fluorescence lifetime and of the total intensity of the broadband measured in YAG and Al₂O₃ indicate that the radiative decay times from the excited states are nearly constant in the range 10–300 K. This demonstrates that the broadband radiative emissions in Ti³⁺:YAG and Ti³⁺:Al₂O₃ are due to magnetic dipole transitions or to electric dipole transitions induced by static odd-parity distortion, respectively. The decrease of the fluorescence lifetime with increasing temperature in Ti³⁺:YAG and Ti³⁺:Al₂O₃ is due to non-radiative decay from the excited state which occurs through phonon-assisted tunnelling between the excited and ground states. The radiative decay of Ti³⁺:YAP is enhanced with increasing temperature, indicating that radiative decay rate contains a term associated with odd-parity phonons. Nevertheless, a non-radiative decay rate of 3.6 × 10⁴ s^–1 observed in the temperature range 10–300 K is due to excited state absorption, which depopulates the excited state and quenches the fluorescence at the laser wavelength.     

原子内壳层双光子衰变的相对论效应和屏蔽效应

本文系统地计算了H原子,类H-Xe离子及Xe原子内壳层的双光子衰变速率。阐明其相对论效应和电子屏蔽效应。并与最新的实验结果和他人的理论计算结果进行了比较和分析讨论。 关键词：     

Luminescence spectra of solid xenon excited by volume discharge

The luminescence spectra of solid xenon excited by a volume discharge are studied for the first time. The majority of the energy is emitted in the VUV spectral region due to the radiative decay of excitons. A specific feature of the spectra in the UV and visible regions is the complete absence of lines belonging to neutral excited particles (one-center Xe* and two-center Xe ₂ ^* excitons) and to diatomic Xe ₂ ⁺ ions. Numerous lines of the Xe⁺ ion are shifted by 0.1–0.3 nm with respect to their positions in the gas; the larger the shift, the stronger the distortion of the line shape. Based on the data obtained, a mechanism by which solid xenon is excited and ionized by fast drifting electrons is proposed.     

Wide-band exciplex halogen lamps operating on inert gas mixtures with chlorine and Freon-12 molecules

The results of analysis of the spectral characteristics of short-wave radiation sources operating on transitions in argon, krypton, and xenon monohalogenides, as well as chlorine molecules, excited by a longitudinal low-pressure glow discharge are considered. Radiation emitted by ArCl^*, KrCl^*, XeCl^*, Cl ₂ ^** , and Cl ₂ ^* molecules in a spectral range of 170–350 nm is optimized using complex working mixtures of Ar-Kr-(Xe)-Cl₂ in the lamps. The average radiation power of the lamps ranges from 1 to 10 W for an efficiency of ≤25%. Optimization of wide-band lamps on transitions in chlorine molecules and the decay products of Freon-12 molecules (CF₂Cl₂) is carried out on mixtures of helium with chlorine and Freon-12 molecules. This makes it possible to develop lamps emitting in a spectral range of 140–270 nm and containing no costly inert gases (Xe or Kr) in their working mixtures. Exciplex halogen lamps with a wide-band emission spectrum in the VUV-UV range can be used in spectrometers as radiation sources in experiments with absorption and in high-energy chemistry, ecology, and medicine.     

The decay of123Xe

The decay scheme of 2.1 h¹²³Xe has been investigated using isotopically separated samples produced by the ISOLDE facility at CERN. A total number of 108 γ-transitions has been observed in this decay, 103 of them have been placed in a level scheme involving 28 excited states in¹²³I. This level scheme is mainly based on the results of γγ-coincidence experiments with two Ge(Li) detectors.     

Der Zerfall des125m Xe,des127m Xe und des127g Xe

The decay of^125m Xe produced by the reaction¹²²Te(α, n)^125m Xe using a target enriched in¹²²Te (95.4%) and the decay of^127m Xe produced by the reaction¹²⁷J(d, 2n)^127m Xe have been investigated: ^125m Xe decays with a half-life ofT _1/2=(56±3) sec by ayy- cascade withE _γ1=(140.4 ±0.5) keV andE _γ2=(110.5 ±0.5) keV. The experimental conversion coefficients yield multipolarities ofE3 for the 140.4 keV isomeric transition and predominantlyM1 for the 110.5 keV-transition. ^127m Xe decays with a half-life ofT _1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofE _γ1=(172.5±0.3) keV and a predominantlyM1 transition ofE _γ2=(124.6±0.3) keV. In the decay of^127g Xe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-captureP _K618/P_K375=0.40 ±0.07 yields a total transition energyQ _EC=(664 ±4)keV. A spin of 1/2⁺ was assigned to the ground state.     

Nuclear magnetic resonance on oriented 11/2− 129mXe and131mXe in Fe

The magnetic hyperfine splitting frequenciesν _M=¦gμ _NB_HF/h.¦ of the 11/2^? isomeric states^129m Xe (T_1/2=8.9d) and^131mXe (T_1/2=11.8d) in Fe were measured with nuclear magnetic resonance on oriented nuclei at temperatures of 10–15 mK as 188.0(1) MHz and 209.8(1) MHz, respectively, the samples being prepared with the technique of recoil implantation after (α, x n) reactions. The magnetic moments of^129m Xe and^131m Xe are deduced to be (?)0.8914(6)μ _N and (?)0.9943(6)μ _N, respectively. The missing γ-anisotropies for allγ-transitions following the decay of 36.4d ¹²⁷Xe indicateI=1/2 for the ground state spin of¹²⁷Xe.     

Single photon decay of double hole states in atoms

The probability of single-photon decay of highly excited double hole state of atoms is considered. The concrete calculations are performed in the lowest order of perturbation theory in interelectron interaction for states (2s)^-2 in Ne, (2s)^-2 and (2p)^-2 in double ionized Ar?Ar⁺⁺ and (4d)^-2 in Xe.     

A Miniaturized XeCl Dielectric Barrier Discharge as a Source of Short Lived,Fast Decaying UV Radiation

A dielectric barrier discharge (DBD) of coaxial geometry has been examined as source of intensive, short‐lived UV radiation. A binary gas mixture consisting of 98% Xe + 2% Cl₂ and a ternary composition of 96% Ne + 6% Xe + 0.2% HCl were investigated in the pressure range between 10 and 750 mbar. The discharge was excited by unipolar high voltage square pulses with amplitudes of 3 to 7 kV at a repetition rate of 100 Hz. UV radiation intensity is increased by combining 5 square pulses with a period of 1 μs each in one train (burst). Radiation decay on three orders of magnitude within 10 μs was obtained for both gas mixtures in burst mode. Maximum energy of the light pulse was the same for both gas mixtures and estimated as 40 nJ. It is shown that the optimum gas pressure for highest radiation intensity depends not only on gas composition but also on applied voltage and number of pulses in the train. A variation of the spectral band shape of XeCl emission during the pulse is detected (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multi-band spectral structure and kinetics of the third continua in Ar,Kr and Xe gases excited by a pulsed discharge

Time-resolved VUV-UV emission of Ar, Kr, and Xe gases (Rg), excited by a pulsed discharge, have been measured to clarify the origin of the 3rd continua. Several detected continuum bands exhibit very different time behaviors due to various atomic (ionic) precursors and plasma kinetics. Imaging experiments with ns-gated ICCD camera have shown that the 2nd continua (Rg₂^*) and Rg^* lines emit uniformly in the positive column of the discharge. However, the 3rd continua and Rg^+* lines were excited exclusively in the negative glow zone, where high-energy electrons are injected from the cathode layer. The multi-band structure of the 3rd continua has been connected with Rg²⁺ ions produced in the ground and different excited states. These precursors lead to the formation of several bound states Rg₂^2+*, which decay radiatively to the repulsive states (Rg⁺ + Rg⁺), where Rg⁺ ions can be on ²P_3/2, ²P_1/2 levels due to spin-orbit coupling. The rate constants for the formation of Rg₂²⁺ excimers in three-body reaction and two-body collisional quenching of Rg^2+∗ ions have been determined from the time behaviors of emission. The quenching of Rg^2+∗ ions is explained by the level crossing between bound (Rg^2+* + Rg) and repulsive (Rg²⁺ + Rg) potential curves.     

Electronic and geometric structure of doped rare-gas clusters: surface, site and size effects studied with luminescence spectroscopy

The electronic and geometric structure of rare gas clusters doped with rare-gas atoms Rg = Xe, Kr or Ar is investigated with fluorescence excitation spectroscopy in the VUV spectral range. Several absorption bands are observed in the region of the first electronic excitations of the impurity atoms, which are related to the lowest spin-orbit split atomic ³P₁ and ¹P₁ states. Due to influence of surrounding atoms of the cluster, the atomic lines are shifted to the blue and broadened (“electronical cage effect”). From the known interaction potentials and the measured spectral shifts the coordination of the impurity atom in Ar_N, Kr_N, Ne_N and He_N could be studied in great detail. In the interior of Kr_N and Ar_N the Xe atoms are located in substitutional sites with 12 nearest neighbours and internuclear distances comparable to that of the host matrix. In Ne_N and He_N the cluster atoms (18 and 22, respectively) arrange themselves around the Xe impurity with a bondlength comparable to that of the heteronuclear dimer. The results confirm that He clusters are liquid while Ne clusters are solid for N≥ 300. Smaller Ne clusters exhibit a liquid like behaviour. When doping is strong, small Rg_m-clusters (Rg = Xe, Kr, Ar, m≤10 ²) are formed in the interior sites of the host cluster made of Ne or He. Specific electronically excited states, assigned to interface excitons are observed. Their absorption bands appear and shift towards lower energy when the cluster size m increases, according to the Frenkel exciton model. The characteristic bulk excitons appear in the spectra, only when the cluster radius exceeds the penetration depth of the interface exciton, which can be considerably larger than that in free Rg_m clusters. This effect is sensitive to electron affinities of the guest and the host cluster.     

Beta-delayed neutrons and high-energy gamma-rays from decay of137I

Beta-delayed neutrons and high-energyγ-rays following decay of¹³⁷I have been studied in order to characterizeβ-decay to and deexcitation of neutron-unbound levels in¹³⁷Xe. The totalγ-ray intensity observed accounts for at least 20% of theβ-intensity to levels aboveB _n . No evidence was found for neutron andγ-ray emission from the same levels. With the experimentalβ-strength function aboveB _n detailed tests were performed on the reproduction of the experimental neutron spectrum, the level density and Porter-Thomas fluctuations of the reducedβ-transition probabilities to highly excited states in¹³⁷Xe.     

Elastic and inelastic scattering of polarized protons from even n=82 nuclei near isobaric analog resonances

Excitation curves for the elastic and the inelastic scattering of polarized protons on the target nuclei ¹³⁸Ba, ¹⁴⁰Ce, ¹⁴²Nd and ¹⁴⁴Sm have been measured in the energy region of prominent isobaric analog resonances. A detailed analysis of the data is presented. Definite J^π assignments are given for a number of parent analog states. Spectroscopic factors and amplitudes for configurations with the core in the ground state or in the 2₁⁺ excited state are derived from the elastic and inelastic proton decay amplitudes. They show consistency with sum rules including orthogonality conditions. Different methods for the-calculation of single particle decay widths have been applied. The qualitative agreement with present unified model calculations is remarkable; an overestimattion of the weak coupling structure, however, becomes apparent.