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.     

Der Zerfall des Xe123,T 1/2=2,08h

Xe¹²³ (T _1/2=2.08 h) was produced by bombarding Te¹²² with 48 MeV α-particles. The radioactive Xe¹²³ gas was collected during irradiation in liquid air cooled glass ampoules. The gamma rays associated with the decay of Xe¹²³ have been investigated using Ge(Li)- and NaJ(Tl)-counters and a Ge(Li)-NaJ(Tl)-coincidence circuit. 57 gamma transitions in the energy range from 148.7 keV to 2559.1 keV have been found. By depositing the radioactive Xe-ions on Ti-foils sources were obtained thin enough to study the conversion electrons using a Si(Li)-counter. The conversion coefficients for the intensive J¹²³ transitions with low energy were determined. A level scheme for Xe¹²³→J¹²³ which accounts for almost all observed γ-transitions having 16 levels is proposed. Furthermore some new data for the J¹²¹ and J¹²³ decay are presented.     

Der Zerfall des Co55,T 1/2=18h

Co⁵⁵ T ^1/2=18 h) was produced by bombarding iron-foiles with 9 MeV deuterons.γ-spectra from the decay of Co⁵⁵ have been investigated using a scintillation fast-slow-coincidence circuit and a Li-drifted Ge-counter. 18γ-transitions were observed having the following energies in keV and intensities per Co⁵⁵-decay:γ ₁=95 (0.006),γ ₂=413 (0.016),γ ₃=475 (0.12),γ ₄=645 (0.005),γ ₅=750 (0.002),γ ₆=810 (0.025),γ ₇=900 (0.024),γ ₈=940 (0.80),γ ₉=985 (0.009),γ ₁₀=1055 (0.005),γ ₁₁=1210 (0.01),γ ₁₂=1320 (0.065),γ ₁₃=1375 (0.042),γ ₁₄=1410 (0.13),γ ₁₅=1600 (0.001),γ ₁₆=1800 (0.0006),γ ₁₇=2160 (0.001),γ ₁₈=2310 (0.0042).     

Nuclear orientation study of the decay of208At (T 1/2=1.63 h) and209At (T 1/2=5.41 h) implanted in iron host

We have measured the angular distribution of gamma-rays in 208,209Po following the decay of the mass-separated isotopes 208,209At polarized at low temperatures in an iron host. Multipole mixing ratios were deduced for 14 and 9 gamma-ray transitions in 208Po and 209Po, respectively, and unambiguous spin-assignments were made for several levels in both nuclei.     

Bestimmung des (631)K=1/2, I=1/2-Zustandes im U 239

Theγ-ray spectrometer at the DR 3-reactor at Risø was used to investigate the low energyγ-lines of U 239 which are emitted during neutron-capture in U 238. Very closely lying lines have been found between 500 and 650 keV. The big intensity of the 133 keV line and the lack of other transitions of appropriate energy and intensity point out that this line corresponds to the hinderedE 2-transition from the (631)I=1/2⁺ level to the (622)I=5/2⁺ groundstate. A suggestion was made for the decay possibility of the octupole states at 700 keV found by N.Fiebiger.     

Nuclear magnetic resonance on oriented194Ir (T 1/2=19.4 h) in Fe and Ni

The hyperfine interaction of¹⁹⁴Ir (j ^π =1^?;T _1/2=19.4 h) in Fe and Ni has been investigated with the technique of nuclear magnetic resonance on oriented nuclei. For both systems the electronic-orbital-momentum induced electric quadrupole splitting could be resolved. The magnetic and electric hyperfine splitting frequencies,v _M =¦gμ _N ^B _HF/h¦ andv _Q =e ² qQ/h, respectively, were measured as:¹⁹⁴IrFe:v _m =408.54 (23) MHz;v _q =?2.47(20) MHz;¹⁹⁴IrNi:v _M =135.24(5) MHz;v _q =?1.23 (3) MHz. Taking into account a 3% uncertainty arising from hyperfine anomalies theg-factor is deduced as ¦g¦=0.39 (1). The electric quadrupole moment,Q=+0.352 (18)b, is slightly smaller than expected from the known systematics of deformation parameters in this mass region.     

Study of Ba 6p1/2ns (J=0,1) autoionizing series

With different polarization configurations the spectroscopic properties of Ba 6p_1/2ns (J=0) and 6p_1/2ns (J=1) autoionizing states have been studied systematically by using an isolated core excitation scheme. Level energies and widths of n members for the J=1 series with n=9–33 and for the J=0 series with n=9–10,12–20 are reported, most of which are observed for the first time. Further information about these two autoionizing series, such as energies of the higher n members and their interseries interactions with 6p_3/2nl series, are obtained by means of saturation excitation method. The experimental data on the J=1 series are analyzed with a 13-channel multichannel quantum defect theory, and general agreement between them has been obtained. Several parts of the experimental results are compared with those of previous works, and agree well with them.     

Optical isotope shift of172Hf (T 1/2=1.87 a)

In the course of preparing experiments with^178m2Hf, optical isotope shifts for the stable Hf isotopes and for¹⁷²Hf were measured. For the rms nuclear charge radii we obtain r²¹⁷² -(r²)¹⁷⁸=–0.242(16) fm².     

钙原子4p_(1/2,3/2)ng(J=3)自电离Rydberg光谱的研究

利用Monte Carlo(MC)方法模拟研究了薄膜生长的初始阶段岛的形貌和岛的尺寸与基底温度和入射粒子剩余能量之间的关系.模型中考虑了粒子的沉积、吸附粒子的扩散和蒸发等过程.结果表明当基底温度从200K变化到260K时,岛的形貌经历了一个从分散生长逐渐过渡到分形生长的过程,并且在较低温度(200K)下,随入射粒子剩余能量的增加,岛的形貌也经历了同样的变化过程.进一步研究证明,随着基底温度的升高或入射粒子剩余能量的增加,沉积粒子的扩散能力显著增强,从而使岛的形貌发生了改变.     

The alpha decay study of223Th (T 1/2=0.6 s)

Correlations between neutrons have been studied in the 96 MeV¹⁸O +⁶⁴Ni reaction, yielding the compound nucleus⁸²Kr at 88 MeV excitation energy. The observed anticorrelation at small relative momenta evidences dominance of quantum-statistical interference between identical particles, from which it is possible to deduce an average source lifetimeτ=(1.2±0.1)·10^?20 s as an upper limit disregarding possible contributions to the correlation function from the competingnn final-state interaction. Lacking appropriate model calculations at present, it is argued that further refinements in the theoretical treatment of strong interactions in the final state are needed to enable truly quantitative conclusions from small-angle nucleon-nucleon correlations at such large timescales.     

Precise measurement of the J = 1 to J = 2 fine structure interval in the 2( 3)P state of helium

We measure the J = 1 to J = 2 fine structure interval in the ( 3)2P state of helium to be 2 291 175.9(1.0) kHz. We use laser excitation of an atomic beam along with an integrated electro-optic modulator technique to obtain this result. The result is consistent (2.9+/-3.2 kHz) with what could be considered an earlier version of this experiment but is not in good agreement ( 20+/-5 kHz and 22+/-8 kHz) with the two other precision determinations of this interval. The current theoretical prediction lies between and overlaps the experiments.     

Helicity Amplitudes for Photoproduction of Baryons with J = 1/2 and JP = 3/2+

We derive the separate helicity amplitudes using the partial wave analysis in the process of pseudo-scalar meson photoproduction. For J^P = 3/2⁺, we find the amplitude is model independent. According to parity conservation, the general amplitude in the case of J^P = 1/2^- is obtained. We prove this general amplitude corresponds to the situation of λ= -1 when adopting the circular polarization. Finally, the formulas of scattering amplitudes involving the meson photoproduction with J^P = 3/2⁺ are obtained from the chiral quark model.     

Die Algebra des Isotopen Spins (3/2, 1/2)

Zusammenfassung Alle irreduziblen Systeme von n hermitischen Matrizen _j, die den zyklischen Vertauschungsrelationen dritten Grades (s. Gl. (14)) genügen, werden explizite aufgefunden. Es zeigt sich insbesondere, dass bei n=3nur zwei solche nichttriviale Lösungen existieren, eine sechsreihige und eine vierreihige. Die erste ist mit dem von Votruba und Lokajíek zwecks Beschreibung des Verhaltens des isotopen Spins des Nukleons eingeführten Matrixsystem äquivalent. Die zweite Lösung erfüllt zugleich auch die Kemmerschen Relationen. Für jedes n>3gibt es nur je eine nichttriviale Lösung, nämlich die Kemmersche von der Ordnung N=n+1.     

Measurement of the nuclear magnetic moment of110Ag(T 1/2=24.4 s)

Nuclear magnetic resonance of¹¹⁰Ag has been observed in silver halides using the polarized neutron capture,β decay anisotropy method. The magnetic moment was determined asμ _I(¹¹⁰Ag)=2.7084 (5) nm (uncorrected).     

Twists in Hopf algebras andRT 1 T 2=T 2 T 1 relations

LetR be a matrix unitary quasi-classical solution of the Yang-Baxter equation. Considering an associative algebra defined by the relationRT ₁ T ₂=T ₂ T ₁ we find a universal twistF such thatR is the image ofR=F ₂₁ F ⁻¹ in the vector representation. Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002.     

Determination of internucleotide (h)J(HN) couplings by the modified 2D J(NN)-correlated [(15)N, (1)H] TROSY

Recent developments in the direct observation of J couplings across hydrogen bonds in proteins and nucleic acids provide additional information for structure and function studies of these molecules by NMR spectroscopy. A J(NN)-correlated [(15)N, (1)H] TROSY experiment proposed by Pervushin et al. (Proc. Natl. Acad. Sci. USA 95, 14147-14151, 1998) can be applied to measure (h)J(HN) in smaller nucleic acids in an E.COSY manner. However, it cannot be effectively applied to large nucleic acids, such as tRNA(Trp), since one of the peaks corresponding to a fast relaxing component will be too weak to be observed in the spectra of large molecules. In this Communication, we proposed a modified J(NN)-correlated [(15)N, (1)H] TROSY experiment which enables direct measurement of (h)J(HN) in large nucleic acids.