On the level scheme of the159Tm nucleus

Level in¹⁵⁹Tm have been excited in the¹⁵⁰Sm(¹⁴N,5n reaction. The yrast band 7/2^?[523] observed up to spin 45/2^? is built on a isomeric state at 166 keV (T _1/2=37±5ns). Connections between the 7/2^?[523] and 7/2⁺ [404] bands fix the band-head energies.     

Levels in159Ho as populated from decay of159Er

The level scheme of the odd proton nucleus¹⁵⁹Ho has been investigated using Ge(Li) and Si(Li) detectors. Results ofγ-ray singles, conversion electron spectra and coincidence experiments are reported. Assignments are made for several energy levels.     

Lifetime measurements in Tm I,Tm II,and Tm III by time-resolved laser spectroscopy

Natural radiative lifetimes of eight levels in Tm I ( 4f ¹³5d6p and 4f ¹²5d6s ² configurations), two levels in Tm II ( 4f ¹²5d6s configuration) and three levels in Tm III (4f ¹²5d configuration) have been measured by using time-resolved laser spectroscopy. Free thulium atoms, as well as singly and doubly ionized ions, were obtained in a laser-induced thulium plasma and the investigated states were selectively populated by a single-step excitation process with a tunable narrow-band laser pulse. Received 20 August 2002 / Received in final form 7 January 2003 Published online 4 March 2003 RID="a" ID="a"e-mail: huailiang.xu@fysik.lth.se     

Der Zerfall von Tm174 und Tm175

The radioactive isotopes Tm¹⁷⁴ and Tm¹⁷⁵ were produced by the reactions Yb¹⁷⁶ (γ, np) Tm¹⁷⁴ and Yb¹⁷⁶(γ,p) Tm¹⁷⁵ respectively, with bremsstrahlung of 54 MeV maximum energy. TheΒ- andγ-radiations from the decay of these isotopes were investigated using scintillation counters, solid state detectors and coincidence methods. The decay scheme proposed for Tm¹⁷⁴ is similar to those proposed by previous investigations. The spin assignment of the isomeric 1520 keV level was revised to beI=7. The decay of Tm¹⁷⁵, which was until now rather unknown, has a half-life of of 15.2±0.5 min. The suggested decay scheme shows excited levels at 105 (9/2^?), 511 (1/2^?), 553 (3/2^?), 598 (5/2^?), 643 (5/2^?, 7/2^?), 816 (3/2^?), 873, 990, 1454 (1/2⁺), 1496 (3/2⁺), 1505, 1810 and 1881 keV. The results are discussed using the Nilsson model.     

Spectroscopic characteristics of Tm3+ in Tm and Tm,Nd, Yb:Sc2O3 ceramic

The spectroscopic investigation of Tm³⁺ or (Nd, Yb, Tm)-doped Sc₂O₃ transparent ceramics, as laser-active media for visible and IR emission, was performed. The spectra are dominated by Tm³⁺ ions in sites of C₂ symmetry and an energy level scheme and other spectral parameters were determined. The strong concentration quenching of ³H₄ level emission in Tm:Sc₂O₃ at 300 K is discussed by considering the resonant cross-relaxation (³H₄→³F₄)?(³H₆→³F₄) process and multipolar interactions of various orders. The main energy-transfer processes leading to the blue upconversion emission from the ¹G₄ Tm³⁺ level in (Tm, Nd, Yb):Sc₂O₃ ceramic, under pulsed pumping at 808.3 nm were evidenced.     

Description of the Triaxial Strongly Deformed Bands in 160,161Tm and 163Tm

Properties of the triaxial strongly deformed （ TSD） bands of 160,161 Tin and 163Tm are investigated systematically within the supersymmetry scheme including ma~y-body interactions and a perturbation possessing SO（5）（or SU（5）） symmetry on the rotational symmetry. Quantitatively good results of the γ-ray energies, the dynamical moments of inertia and the spin of the TSD bands in 160,161Tm and 163Tm are obtained. The calculation shows that competition between the pairing and anti-pairing effects exist in these TSD bands. Meanwhile, the SU（3） symmetry in TSD bands is broken more seriously than that in superdeformed bands.     

169Tm Mössbauer experiments in the paramagnetic phase of Tm2 Al

Magnetic and Mössbauer measurements have been made on the intermetallic compound Tm₂ Al from 1.4 to 300 K. The susceptibility data show Curie—Weiss behaviour with an effective magnetic moment of 7.7(1) μ_B per atom, cf. the free ion value of 7.56 μ_B. No evidence of magnetic ordering is found down to 1.4 K. By way of contrast, however, the¹⁶⁹Tm Mössbauer data at 1.4 K reveal two fully split six-line spectra, with differing magnetic and quadrupole hyperfine parameters. By 4.2 K, the weaker of the two sub-spectrum has collapsed to form a peak in the centre of the Mössbauer spectrum. At higher temperatures the intensity of the split sub-spectrum slowly disappears, while retaining a virtually temperature-independent magnetic splitting. Both the Tm sites in Tm₂Al therefore exhibit typical para-magnetic relaxation behaviour, with little or no cross-talk between the two Tm species. As with both TmAl and Tm₃Al₂, Tm₂Al exhibits unusually long relaxation times for a metallic material.     

Properties of the lowest states in the odd-odd160Tm and160Tm nuclei

Detailed study of the lowest states in the odd-odd¹⁶⁰Tm and¹⁶²Tm deformed nuclei and of corresponding electromagnetic transitions has been performed. In the theoretical analysis, performed within the framework of the two-quasiparticle + rotor model, the nondiagonal matrix elements of the residual p-n interaction have been included. Comparison of calculated energies and reduced transition probabilitiesB(XL) with experimental ones have proved importance of these matrix elements in the model calculations. More complex interpretation of the lowest states in both Tm nuclei has been achieved although some ambiguity has not been removed.     

High-power diode-end-pumped Tm：YAP and Tm：YLF slab lasers

Diode-end-pumped continuous-wave(CW) Tm:YAP and Tm:YLF slab lasers are demonstrated. The a-cut Tm:YAP and Tm:YLF slabs with doping concentrations of 4 at.-% and 3.5 at.-%,respectively,are pumped by fast-axis collimated laser diodes at room temperature. The maximum CW output powers of 72 and 50.2 W are obtained from Tm:YAP and Tm:YLF,respectively,while the pump power is 220 W,corresponding to the slope efficiencies of 37.9% and 26.6%,respectively.     

Signature inversion caused by triaxiality and unpaired band crossings in 72Br

High-spin states in 72Br were studied with the EUROBALL III spectrometer using the 40Ca(40Ca,alpha3p1n) reaction. The negative-parity band observed in this experiment displays a signature inversion around spin I = 16. The interpretation within the cranked Nilsson-Strutinsky approach shows that this signature pattern is a signal of a substantial triaxial shape change with increasing spin where the nucleus evolves from a triaxial shape with rotation about the intermediate axis at low spin through a collective prolate shape to a triaxial shape but with rotation about the shortest principal axis at high spin.     

Tm valency and magnetism in TmTe

Measurements of the room-temperature lattice parameter and the temperature dependence of the magnetic susceptibility reveal a broad homogeneity range for the possible chemical composition of TmTe and indicate varying valence of the Tm ions as a function of chemical composition. As evidenced by magnetic susceptibility and thermal expansion, TmTe orders at very low temperatures, probably antiferromagnetically and the magnetic ordering temperature also appears to depend on stoichiometry.     

High-spin isomers in W and Os nuclei; Competition betweenK-quantization and triaxiality

Results of a search for high-spin isomers in W and Os nuclei withN=104–107 are presented. Targets of⁴⁸Ca and^{48, 50}Ti are bombarded with a pulsed¹³⁶Xe beam, and delayed gamma-radiation is detected by an array of NaI- and Ge-detectors. Several new isomers, with spin values up to ～22h, are found in^178,180W and^{180, 182, 183}Os. Markedly different decay patterns and hindrance factors are found in the Os isotopes as compared to the expectations based on theK-selection rule valid for axially symmetric nuclei. The findings are ascribed to the onset of triaxial distortions.     

Quadrupole splitting observed in some cubic Tm compounds by169Tm Mössbauer spectroscopy

The cubic CsCl structure compounds TmCu, TmAg and TmRh show a quadrupole splitting above their ordering temperatures. Quadrupole pair and magnetic parameters are determined for TmCu in the ordered state.     

TheEC-decay of170Tm

The spectrum ofK X-rays andγ-rays following the decay of¹⁷⁰Tm has been reinvestigated using a high resolution Si(Li) detector. The intensities of theEC-branches from the ground state of¹⁷⁰Tm to the ground state as well as to the first excited level in¹⁷⁰Er have been measured. The total intensity of theEC-decay is (0.25 ± 0.05)% of all¹⁷⁰Tm disintegrations with (0.18 ± 0.05)% leading to the ground state and (0.07±0.02)% leading to the first excited level of¹⁷⁰Er. The energy of the de-excitingγ-ray has been determined to (78.7±0.5) keV. Its intensity is (0.28 ± 0.06)% of that of the 84.3 keVγ-ray in¹⁷⁰Yb.