Der Zerfall der Cäsiumisotope Cs129 und Cs130

Cs¹²⁹(T_1/2=32 h) and Cs¹³⁰(T_1/2=30 min) were produced by J¹²⁷(α,2n)Cs¹²⁹and J¹²⁷(α,n)Cs¹³⁰reactions, respectively. The γ-ray-spectra from the decays of Cs¹²⁹ and Cs¹³⁰ have been investigated using Li-drifted Ge-counters and scintillation spectrometers. In the decay of Cs¹²⁹15 γ-rays have been observed having the following energies and relative intensities: 95 keV (1.6), 177 keV (1.1), 267 keV (1.7), 278 keV (4.8), 317 keV (7.6), 371 keV (100), 410 keV (69), 511 keV (≦ 0.1), 548 keV (10.5), 587 keV (1.7), 623 keV (0.12), 660 keV (0.07), 864 keV (0.09), 907 keV (0.67) and 948 keV (0.2). The electron capture branching ratios to the ground state and excited states of Xe¹²⁹were determined; logft values for the various decay branches were derived from these ratios. In the decay of Cs¹³⁰twoγ-transitions with the following energies and intensities relative to the β⁺ emission have been found: 535 keV (11) and 585 keV (1.3). A new level at 1122 keV in Xe¹³⁰is proposed.     

Isotope shift in the resonance lines of the arc spectrum of133Cs,135Cs,and137Cs

Reactor Cs and mixtures of electromagnetically enriched Cs were used to investigate the isotopic shift of the two resonance lines. By a digital evaluation method anomalies in the isotope shift were found.     

Determination of the isotopic shift of the first resonance line in Cs(I) spectrum for the isotopes 131Cs, 132Cs,and 136Cs

The isotope shifts of the resonance line $\text{λ = 8521}\text{A}\text{?}$ of ¹³¹Cs, ¹³²Cs, and ¹³⁶Cs with respect to ¹³³Cs were determined by a new scanning technique to be $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{131}\text{Cs}\text{) = +1.70(40)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{132}\text{Cs}\text{) = ?0.95(80)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{136}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{) = ?4.0(3.0)}\text{mK}$. In accordance with results from other Cs isotopes and neighbouring elements they show the change 〈δr²〉 in the second radial moment of the nuclear charge distribution to be a factor of 5 to 10 smaller than expected from the model of uniform charge distribution. Integral isotope shifts over the isotopic chains of Xe, Cs, and Ba were analyzed in terms of collective models. Assuming an isotopic shift discrepancy of 0.5 for the nuclear volume shift it was possible to derive deformation parameters $\text{〈β}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in quantitative agreement with those from B(E2) measurements.     

The decay of Cs

In a study of the level scheme of ¹³¹Cs, we have measured the γ-γ and the ce-γ directional correlations of the 496-123.7 keV and 486-133.5 keV cascades. The linear polarization at φ=90° was measured for the 496-123.7 keV and 486-133.5 keV cascades. The L-subshell ratios for the 123.7 keV transition were determined. The g-factor of the 133.5 keV level and the half-lives of the 78.7, 123.7, 133.5 and 216 keV levels were re-investigated. The spin and parity assignments derived for the 620, 133.5 and 123.7 keV levels are , respectively. The 620, 496, 486, 133.5 and 123.7 keV transitions are found to be of pure E2, pure M1, pure E2, (M1+(22±2)%E2) and pure E2 multipolarity, respectively. An upper limit of 192 ps for the half-life of the 216 keV level is obtained. The results are compared with theoretical estimates from the calculations of Kisslinger and Sorensen, of Freed and of Freed and Miles.     

ГАММА-СПЕКТР ИЗ РАДИА ЦИОННОГО ЗАХВАТА НА Cs

The measurements of the -ray spectra, following resonance, neutron capture in¹³³Cs, performed with the aid of the Ge(Li) detector of active volume about 12 cm³, are described. The energies and intensities of a number of transitions have been obtained.

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On leave fromFaculty of Mathematics and Physics, Charles University, Behová 7, Praha 1, Czechoslovakia.

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On leave fromNuclear Research Institute, Czechosl. Acad. Sci., e, Czechoslovakia.     

132Cs gamma radiation

The decay of¹³²Cs was studied by means of Ge(Li) detectors and a magnetic beta-ray spectrometer. The energies and intensities of the transitions in¹³²Xe and¹³²Ba were determined. Of the decay schemes proposed hitherto, that of Johnson et al. [Phys. Rev.138 (1965), B 520] was confirmed.     

Cross section for the resonant charge exchange Cs++Cs at thermal energies

A remeasurement of the cross section for the resonant charge exchange Cs⁺ ?Cs at thermal energies is presented which reduces some of the ambiguities left open in previous studies.     

Study of the133Cs(γ,n)132Cs reaction

The photoneutron spectrum from the¹³³Cs(γ, n)¹³²Cs reaction induced by 9.720 MeV neutron capture gamma-rays has been studied with a³He-spectrometer. The energies and relative intensities of the emitted neutrons were determined. AQ-value of 8,986 +/?2 keV is suggested. The data reveal the existence of seventeen excited states in¹³²Cs in the region up to 551 keV.     

125Cs的能级结构

通过116Cd(14N,5n),Ebeam=65MeV的核反应布居了125Cs的高自旋态.利用在束γ谱学实验方法,进行了γ-γ符合测量,使已知的125Cs核能级纲图得到了扩展,并且修正了某些组态的带头激发能.High-spin states in odd-A nucleus~(125)Cs have been studied via the~(116)Cd(~(14)N, 5n) reaction at 65 MeV bombarding energy. γ-γ coincidences were recorded with the NORDBALL detector array at Niels Bohr Institute in Denmark. After careful data analysis, most of the previously-known bands have been confirmed and 5 new rotational sequences have been identified. Spin/parity and configuration assignments are tentatively proposed for all of the observed bands. In addition, the bandheads of the 9/2~(+)and (1/2~...     

Rotational structures in 123Cs

High-spin states in ¹²³Cs, populated via the ¹⁰⁰Mo ( ²⁸Si, p4n) fusion-evaporation reaction at E _lab = 130 MeV, have been investigated employing in-beam γ-ray spectroscopic techniques. Rotational bands, built on πg _7/2, πg _9/2 and the unique-parity πh _11/2 orbitals, have been extended and evolve into bands involving rotationally aligned ν(h _11/2)² and π(h _11/2)² quasiparticles. A three-quasiparticle band based on the high-K πh _11/2 ⊗ νg _7/2 ⊗ νh _11/2 configuration has also been observed. Total Routhian Surface (TRS) calculations have been used to predict the nuclear shape parameters ( β₂, β₄, γ) for the various assigned configurations. The assigned configurations have been discussed in the framework of a microscopic theory based on the deformed Hartree-Fock (HF) and angular-momentum projection techniques.     

Collective properties of129Cs

High-spin properties of¹²⁹Cs have been investigated following¹¹⁶Cd(¹⁸O, p4nγ) and¹²²Sn(¹¹B, 4nγ) reactions. Rotational bands built on h_11/2,g_7/2, and d_5/2 singleproton states were observed. At higher spins, band-crossings attributed to the alignment of h_11/2 neutrons were observed. A comparison with total Routhian cranking calculations support this interpretation.     

New compounds with incommensurate phases: Cs2CdI4 and Cs2ZnI4

Abstract

In this paper the results of birefringence studies and of optical observations in polarized light in a wide temperature region are presented for crystals Cs₂CdI₄ and Cs₂ZnI₄. There is the following sequence of phases: commensurate orthorhombic Pnma ? incommensurate ? monoclinic ferroelastic P2₁/n ? triclinic ferroelastic PT. A correlation was observed between the peculiarities of birefringence and NQR spectra temperature dependence. An assumption is made, that in Cs₂ZnI₄ crystal in a broad pre-transition region (T - T _i = 100 K) precursor clusters exist, which manifest themselves as coexistence of NQR spectra of two phases and as deviation of birefringence from the linear temperature dependence (“tail”).     

Decay of Cs134m

The decay of the isomeric state of Cs¹³⁴ was studied. The decay half-timeT _1/2=2·93±0·05 hours was determined. From measurements carried out by means of a spectrometer with short lens, scintillation measurements and chemical separations, the non-existence of the weak decay of this state was proved, contrary to statements found previously in the literature (maximum possible intensity 0·02%, compared to the value of 1% found in the literature). The spectrum of conversion electrons was measured by a double-focusing spectrometer, and the following transition energies were determined: 127·3±0·3 keV (E3) and 138·4±0·4 keV (M4) (K:L:M+N is 92 100 27 for the 127·3 keV transition, and 206 100 31 for the 138·4 keV transition). The conversion coefficient of the 127 keV transition was measured, resulting in a value of _k =2·55±±0·4. The ratio of transition intensities isI ₁₃₈ I ₁₂₇=5·7 1000.     

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.     

Bestimmung des Wirkungsquerschnitts σ(Cs+→Cs) aus Sondenmessungen in einem thermischen Cs-Plasma

The ion currentI _i to a Langmuir probe was measured in a Cs-plasma which was produced by contact ionization and for which the neutral densityn _g is known and the plasma density is given by the Saha equation. Using the theory of Self and Shih the collision cross section σ(Cs⁺→Cs) was calculated from the measured ion currentI _i .     

Electronic structure and metal-nonmetal transition in liquid Cs−Sb and Cs−I systems

The electronic structures of liquid Cs–Sb and liquid Cs–I systems have been calculated using the self-consistent semirelativistic APW method within the superlattive model. We have investigated the nature of chemical bonding in connection with the composition dependent metal-nonmetal transition in these systems. It is found that Cs–Sb system is principally ionic as well as Cs–I system, but appreciable admixture of the metallic bonding is observed; this explains the different behavior between the two systems in their composition-induced metal-nonmetal transitions.     

126Cs的高自旋态能级结构

利用融合蒸发反应¹¹⁶Cd(¹⁴N,4n)¹²⁶Cs布居了¹²⁶Cs的高自旋态.观测到了100多条新的γ跃迁和相应的能级,建立了双奇核¹²⁶Cs由9个转动带构成的能级纲图.尝试性地指定了大部分能级的自旋和宇称以及各转动带的Nilsson单粒子组态.极大地丰富了已有的实验结果.     

Luminescence of Cs2PtF6

In the past five years, a number of d⁶ complexes have been found to exhibit luminescence when excited by ultraviolet light. Such emission has been assigned to d-d transitions localized on the metal ion, to charge-transfer transitions, and to ligand localized transitions^2,3. The specific kind of emission observed is thought to depend on which electronic level lies lowest in energy.     

New excitation scheme of 139Cs

¹³²Te was produced via the ²³²Th (α, fission) reaction at the Variable Energy Cyclotron , Calcutta. ¹³²Te was separated in carrier-free form from the fission products by radiochemical separation and the half-lives for the 50 keV and 162 keV states of ¹³²I were determined to be 2.94±0.11 ns and 0.55±0.04 ns respectively. The present results differ significantly from the previously reported half-lives of 7.14 ns and 3.57 ns for the 50 keV and 162 keV states respectively. Received: 28 July 1998 / Revised version: 23 September 1998