Gyromagnetic ratios of 4+ and 6+ states in156Gd and158Gd

The followingg-factors have been derived from time integral measurements of γ-γ angular correlations in the static magnetic hyperfine field of magnetized gadolinium metal probes:¹⁵⁶Gd:g(4 ₁ ⁺ )=+0.310(19)g(6 ₁ ⁺ )=+0.25(21)g(4 ₃ ⁺ , 1511 keV)=+0.809(27)¹⁵⁸Gd:g(4 ₁ ⁺ )=+0.409(15). The 5.35d ¹⁵⁶Tb sources were produced by the reaction¹⁵⁶Gd(d, 2n)¹⁵⁶Tb in our cyclotron. A carrier-free 150y ¹⁵⁸Tb source was obtained from ISOLDE/CERN. In comparison with the precisely knowng-factors of the 2 ₁ ⁺ states,g(2 ₁ ^su+ ,¹⁵⁶Gd) =+0.386(4) andg(2 ₁ ⁺ ,¹⁵⁸Gd)=0.381(4), we observe a large reduction for the¹⁵⁶Gd 4 ₁ ⁺ state whereasg increases slightly for¹⁵⁸Gd. The half-life of the 4 ₁ ⁺ state of¹⁵⁸Gd was remeasured as¹⁵⁸Gd:T _1/2(4 ₁ ⁺ )=148(2) ps. A measurement of the rotation in the 4 ₃ ⁺ state of¹⁵⁶Gd in external magnetic fields of various strengths up toB _ext=9.5 T did not confirm the anomalous dependence of the magnetic hyperfine field in gadolinium metal on the external field, which has been reported by Persson et al. [29].     

g-factor of the first excited 4+ states in156Gd and158Gd

Relative g-factor of the first 2⁺ and 4⁺ states have been measured with the transient field technique in¹⁵⁶Gd and¹⁵⁸Gd. The precession of gamma rays depopulating the levels under study were observed, after passing through thin polarized gadolinium. The observed values agree with the predictions of the rotational model, i.c. g(4⁺)= g(2⁺), while contrasting the hypothesis that in¹⁵⁶Gd the g-factor of the 4⁺ is reduced with respect to the 2⁺, because of rotational alignment.     

Remeasurement of the half-life of the 589 keV state of117in and reevaluation of itsg-factor

Difficulties in the interpretation of a recent IPAC result for theg-factor of the 589 keV state of₁₁₇In prompted us to remeasure its half-life. The value,T _1/2=92(16)ps quoted in the literature, which is the average of three independent and well agreeing measurements, was not confirmed. The half-life was found to be at least one order of magnitude smaller. This result solves the puzzle of theg-factor.     

Determination of the lifetime of the 4p 1/2-state of potassium by Hanle-effect

The lifetime of the first excited 4P _1/2-state of potassium has been determined to be τ=27.3(3) nsec by investigating the intensity of the scattered resonance light of the potassiumD ₁-line as a function of a magnetic field. From this result the absorption oscillator strength of theD ₁-line of potassium could be deduced to bef=0.326(4).     

Measurement of theg-factor of the 4 1 + -state of202Pb

Theg-factor of the 4 ₁ ⁺ -state of²⁰²Pb was investigated by the IPAC-technique. Inspite of the long half-life, which was measured as:T _1/2(4 ₁ ⁺ -state)=1.97(2)ns and the strong applied external magnetic field of 95.0 kG no rotation of the 787 keV-(422keV)-961 keVγ-γ angular correlation could be observed. Theg-factor must therefore be very small. A computer fit gave the limits:g(4 ₁ ⁺ -state)=+0.002(4). This smallg-factor can be understood by the assumption of an accidental cancellation of a positive contribution by the main [f _5/2 ² ]₄-configuration and several negative contributions by admixtures of all other possible two neutron configurations.     

Band mixing in156Gd and158Gd

A detailed investigation of the energies and intensities of the γ-rays that depopulate the low spin levels of the β- and γ-vibrational bands of¹⁵⁶Gd and the γ-vibrational band of¹⁵⁸Gd has been conducted. Both singles and γ-γ coincidence measurements were made on sources of 15-d¹⁵⁶Eu and 46-min¹⁵⁸Eu by use of large volume, high resolution Ge(Li) detectors. In addition to the γ-band at 1154.09 keV, twoK ^π=0⁺ bands were observed in¹⁵⁶Gd with band heads at 1049.45 and 1168.11 keV, respectively. The 2⁺ and 3⁺ members of the γ-vibrational band in¹⁵⁸Gd were observed at 1187.12 and 1265.43 keV, respectively, as well as a newK ^π=0⁺ band at 1195.98 keV. A first order perturbational treatment of the branching ratios was applied to both nuclei. In addition, the mixing between the ground state, the β-, and the γ-vibrational bands of¹⁵⁶Gd is considered from two approaches, but neither satisfactorily explains all the experimentalB(E2) ratios.     

Theoretical analysis of S1-state lifetime measurements of dyes with picosecond laser pulses

Various methods for the determination of the S₁-state lifetime of dye solutions (laser dyes and modelocking dyes) are analysed. A general model of interaction of laser light with dye molecules is presented and reduced to a dye energy level scheme of six levels. Fluorescence emission, light amplification and absorption recovery techniques are investigated theoretically and their limitations revealed. The determination of the S₁-state lifetime of saturable absorbers by single picosecond pulse bleaching experiments is very thoroughly discussed. The influence of various laser and dye parameters on the bleaching experiments are analysed numerically. The results are compared with isotropic steady state two- and three-level dye models.     

Mössbauer-effect studies of excited states of 155Gd, 156Gd and 157Gd

Mössbauer-effect studies yield the following nuclear parameters: In ¹⁵⁵Gd, Q(86)/Q(0) = 0.087 ± 0.006, Q(105)/Q(0) = 1.00 ± 0.03. In ${}^{156}\text{Gd}\text{, g(89) = 0.386 ± 0.004,}{}^{156}\text{Q(89)/}{}^{155}\text{Q(0) = ?1.51 ± 0.02.}\text{In}{}^{157}\text{Gd}\text{, Q(64)/Q(0) = 1.80 ± 0.03}\text{and}\text{g(64) = ?0.185 ± 0.005}$. The value of g(89) is in very good agreement with the theoretical value.     

Description of multi-band structures in154Gd and156Gd on symmetry considerations

The observed similarities of the yrast band level energies of several pairs of lighter rare-earth even-even nuclei are indicative of a particle-hole type symmetry for nuclei withA =164±a. This feature is sought to be described in terms of the representations of theSU(7) group in the interacting Fermion picture.SU(3) reduction of this group leads to the prediction of characteristic multi-band structures in these nuclei. Detailed comparison of the single-parameter predictions of this scheme with the available experimental informations on the level schemes for the nuclei¹⁵⁴Gd and¹⁵⁶Gd reveals striking agreement between the theory and the experiments. The results are discussed in comparison with the predictions of the simple Interacting Boson Model.     

One-dimensional 3-state and 4-state standard Potts models in magnetic field

The exact solutions for 3-state and 4-state standard Potts models in external magnetic field are obtained within the framework of the Kramers-Wannier transfer matrix. The explicit analytical expressions for thermodynamic quantities such as magnetization, magnetic susceptibility and specific heat are derived and analysed at length as functions of temperature and magnetic field.     

Investigation of statistically perturbed angular correlations of154Gd and156Gd in different liquid sources

The statistical perturbations of γγ-angular correlations involving the first 2⁺ rotational state of¹⁵⁴Gd and¹⁵⁶Gd have been time differentially investigated. We used liquid sources of 3⁺ ions of Gadolinium in lN perchloric acid, 0.5 N and 1N hydrochloric acid, 1.3N and 2.6 N sulfuric acid. Influences of the various chemical surroundings on the ratio λ₄/λ₂ of the attenuation parameters have been found. A simultaneous measurement of the angular correlation of the 874 keV–123 keV cascade and the 2,098 keV–89 keV cascade of¹⁵⁴Gd and¹⁵⁶Gd, respectively, has been performed in perchloric solution. From the ratio of the attenuation parameters λ₂, obtained by this experiment, we have derived the ratio of the magneticg-factors of the first 2⁺ levels of these isotopes asg ¹⁵⁴/g ¹⁵⁶=1.11±0.08.     

Study of form factors for single-proton transfer reactions on152Sm,154Gd and156Gd

The (³He,d) and (α,t) single-proton transfer reactions on targets of¹⁵²Sm,¹⁵⁴Gd and¹⁵⁶Gd were studied at 35MeV incident energy. Differential cross sections of rotational states built upon various single-proton configurations are compared with results of DWBA calculations which employed various radial form factors. The agreement between calculated and measured reaction cross sections is found to improve significantly when the commonly used spherical bound-state potentials are replaced by deformed ones, including deformed Coulomb and spin-orbit wells, and projected form factors are used to calculate DWBA cross sections. Discrepancies in the differential cross sections so large that they cannot be attributed to band mixing phenomena are readily explained by form factor effects.     

Hyperfine structure of the 4s4p1P1-state of67Zn by level crossing spectroscopy

The magnetic dipole coupling constantA of the 4s 4p¹P₁ state of⁶⁷Zn was measured in a level crossing experiment. The result is A(4s4p¹P₁ ⁶⁷Zn)= 17.7(5) MHz. In a modified Breit-Wills theory thisA factor leads to a parameter λ_P= 0.71(3), which describes the difference in the radial wave functions of thep-electron in 4s4p¹P₁ and³P₁ states respectively. The lifetime of the 4s4p¹P₁ state was remeasured by Hanle-effect experiments. The result τ=1.41± 0.04 nsec is in good agreement with other measurements.     

Critical Point of the 152Sm, 154Gd,and 156Dy Isotones

Physics of Atomic Nuclei - The even—even rare-earth nuclei in U(5)—SU(3) region at neutron number (N) = 90, have been systematically studied using the Bohr—Mottelson Model (BM),...     

Search for the newM1 mode in156Gd by inelastic proton scattering at low incident energy

The α-decay study of mass-separated nuclei in the region around Z=82 provides a strong spectroscopic tool to investigate intruder states. In this note, this method is applied to the¹⁹⁷At isotope.     

Measurements of lifetime andg-factor of the 32S(4 1 + ) state at 4.459 MeV

Precessions of the very short-lived 2 ₁ ⁺ - and 4 ₁ ⁺ -states in³²S have been measured using the transient field technique. The deducedg-factor of the 4 ₁ ⁺ -state g=+0.40(15) agrees with the known value of the 2 ₁ ⁺ -state and with theoretical predictions. In addition, the lifetimes of both states were redetermined and are consistent with previous results.     

KAIF4：Ce,Gd磷光体的荧光特性及能量传递

采用溶液反应和固相反应,分别合成了ＫＡＩＦ４基质化合物及ＫＡＩＦ４：Ｇｄ、ＫＡＩＦ４：Ｃｅ,Ｇｄ等磷光体,研究了它们的光谱特性。结果表明,ＫＡＩＦ４：Ｇｄ无认顷皮或长波紫外辐激发下,均无任何吸收和发射。在ＫＡＩＦ４：Ｃｅ,Ｇｄ中,Ｃｅ＾３＋离子能有效地将能量传递给Ｇｄ＾３＋离子,使Ｇｄ＾３＋产生了特征锐发射,具发射强度很大。但当Ｃｅ＾３＋浓度固定不变,改变Ｇｄ＾３＋的＾６Ｐ１／２→＾８Ｓ７／２发射     

High resolution spectroscopy of prompt and metastable decaying levels in highly ionized argon,especially of the metastable3 P 2-state of Ar16+ and the4 P 5/2-state of Ar15+

Besides the prompt x-ray emission of Ar-ions, the metastable decay of the heliumlike³ P ₂- and the lithiumlike⁴ P _5/2-levels of highly ionized Ar¹⁶⁺ and Ar¹⁵⁺ atoms has been observed in a foil-excited beam using a flat-crystal spectrometer. Due to the highx-ray energy resolution of the spectrometer the two³ P ₂ →¹ S ₀ and⁴ P _5/2 →² S _1/2 transitions could be resolved. The experiment yielded (3128 ±2) eV for the³P₂ → and (3091 ± 2)eV for the⁴ P _5/2 →² S _1/2 transition energy respectively. Using a time of flight technique the lifetimes of the³ P ₂- and the⁴ P _5/2-states were determined to be (1.44 ±0.09)ns and (0.66 ± 0.05) ns.     

在NaGdF4：Tm3+, Dy3+中Gd3+间的能量迁移及Gd3+-Dy3+能量传递量子效率

基于量子剪裁基本原理,通过光谱技术研究NaGdF₄:Tm³⁺,Dy³⁺在一个真空紫外光子激发下获得两个蓝色光子的可能性。在这种化合物中,量子剪裁通过下转换,即通过应用不同镧系离子间的能量传递进行。通过对Tm 4f¹²-4f¹¹5d激发,部分能量从Tm³⁺离子5d态直接传递给Gd³⁺,然后在Gd³⁺-Tm³⁺之间发生交叉弛豫,剩余能量从Gd³⁺传递给Dy³⁺,产生两个可见光子发射,一个来自Tm³⁺的¹G₄-³H₆跃迁,另一个来自Dy³⁺的⁴F_9/2-⁶H_15/2跃迁。主要研究获得以NaGdF₄:Tm³⁺,Dy³⁺为基础的新型具有更高效率,更高稳定性和更强真空紫外(VUV)吸收量子剪裁发光粉的可能性。各种光谱技术,如光致发光、激发和衰减等被用来表征不同Dy³⁺浓度掺杂NaGdF₄中Gd³⁺晶格间能量迁移引起的施主Gd³⁺和受主Dy³⁺之间的能量传递。结果表明Gd³⁺离子之间存在能量迁移,随之交换相互作用引起施主与受主(Gd³⁺-Dy³⁺)之间的能量传递。通过Bursh-tein等人关于激发态的弛豫理论,施主-受主能量传递参数k_DS可以从Gd³⁺的⁶P_7/2发射的衰减计算出。Gd³⁺-Dy³⁺能量传递量子效率也可以得到。NaGdF₄:Tm³⁺和NaGdF₄:Tm³⁺,Dy³⁺是由水热法制备的,NaGdF₄:Dy³⁺是由文献[4]方法制备的。发射光谱和激发光谱通过自制的VUV光谱仪和F-4500测量。衰减曲线由OPO激光器激发获得Gd³⁺-Dy³⁺之间能量传递量子效率在受主浓度大约在N_A=0.6%时达到最佳值,并且明显地观测到浓度猝灭效应。