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1.
The decay of149Pr (T 1/2=2.2 min) has been studied using the two fission product separators JOSEF and LOHENGRIN to produce the149Pr nucleus. A level scheme for149Nd has been established. Theβ-branching and logft values for the excited levels were deduced from the analysis ofγ-intensity balances. Furthermore, the spins and parities for most of the excited states observed were obtained from the comparison between the present work, the neutron capture results and the pick-up reactions. The positive parity levels have been described with the Nilsson model with Coriolis andΔN=2 interactions included. The properties of the negative parity states cannot be explained as easily; however, it has been attempted to extract the structure of the ground state \((I^\pi = \tfrac{5}{2}^ - )\) and the first excited states \((I^\pi = \tfrac{7}{2}^ - and\tfrac{3}{2}^ - )\) .  相似文献   

2.
Coulomb excitation byα-particles of vibrational-like states in even-mass rare-earth nuclei is used to determine the reduced transition probabilitiesB(E2; 0 gs + →2 γ + ),B(E2; 0 gs + →2 β + ),B(E2; 2 gs + →0 β + ) andB(E2; 0 gs + →3 oct ? ) in150Nd,152, 154Sm,154, 158Gd,164Dy and166Er. TheB(Eλ; 0 gs + I=λ)-values range from 2.4 to 6.5 single-particle units for transitions to the 2 γ + -states, 0.8 single-particle units for the 2 β + -states and from 14.1 to 21.7 single-particle units for the 3?-states.  相似文献   

3.
4.
The rare decay K L 0 → π0ν $ \tilde v $ branching ratio measurement is one of the clearest Standard Model test. Calculations based on the SM predict Br(K L 0 → π0ν $ \tilde v $ ) ≈ 2.8 × 10?11, but the most accurate experimental value Br(K L 0 → π0ν $ \tilde v $ ) < 6.7 × 10?8 (90% C.L.). We present design of a new experimental setup KLOD (U-70 accelerator, IHEP, Protvino) for K L 0 → π0ν $ \tilde v $ branching ratio measurement. Sensitivity of the KLOD experiment will be enough for registration of 2.4 events K L 0 → π0ν $ \tilde v $ for every 10 days of the data taking (according to SM predictions).  相似文献   

5.
The odd-odd 88 37Rb51 and 86 35Br51 nuclei have been produced as fission fragments in the fusion reaction 18O$ + $208Pb at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the triple $ \gamma$ -ray coincidence data and $ \gamma$ - $ \gamma$ angular correlations have been analyzed in order to assign spin and parity values to many observed states. The proposed configurations involve proton excitations from three sub-shells located close to the Fermi levels, $ \pi$ p 3/2 , $ \pi$ f 5/2 , and $ \pi$ g 9/2 , the $ \nu$ d 5/2 neutron acting as a spectator. The residual $ \pi$ $ \nu$ interactions are extracted from the multiplets of states resulting from the $ \pi$ p 3/2 $ \nu$ d 5/2 and $ \pi$ f 5/2 $ \nu$ d 5/2 configurations. The empirical values of the latter are discussed and compared to those known in two similar configurations having j p = j n with l p = l n + 1 , where the role of the tensor force had been highlighted.  相似文献   

6.
The dichloromethanesulfonates of silver and other +1-charged cations, M ?+?(Cl2CHSO $_{3}^{-})$ (M = Ag, Tl, Li, Na, K, Rb, Cs) were synthesized and studied by 35Cl NQR. Dichloromethanesulfonic acid was prepared by the methanolysis of dichloromethanesulfonyl chloride, and was then neutralized with the carbonates of the +1-charged cations to produce the corresponding dichloromethanesulfonate salt. This NQR study completed the investigation of the chloroacetates and chloromethanesulfonates of silver, Ag?+?(Cl x CH3???x SO $_{3}^{-})$ and Ag?+?(Cl x CH3???x CO $_{2}^{-})$ , and suggests (1) that the ability of organochlorine atoms to coordinate to silver decreases as the number of electron-withdrawing groups (Cl, SO $_{3}^{-}$ , CO $_{2}^{-})$ attached to the carbon atom increases; (2) that the unusually large NQR spectral width found among M ?+?(Cl2CHCO $_{2}^{-})$ salts is not present among M ?+?(Cl2CHSO $_{3}^{-})$ salts, and therefore is not generally characteristic of the dichloromethyl group in salts.  相似文献   

7.
Coulomb excitation of the first excited 2+-state was measured usingα-particles to determine reduced transition probabilities,B(E2; 0 gs + →2 1 + ), in nuclei with a closed shell of 82 neutrons. TheB(E2; 0 gs + →2 1 + -values are 10.2 single-particle units (spu) for138Ba, 13.5 spu for140Ce, 11.9 spu for142Nd and 11.6 spu for144Sm. The uncertainty ranges from 1.3 % to 2.3 %.  相似文献   

8.
The abundances of FeII and FeIII environments within green rusts one, GR1s, that intercalate carbonate, oxalate and methanoate (formate) anions are found from Mössbauer spectra for compositions corresponding to [Fe $^{\rm II}_{6}$ Fe $^{\rm III}_{2}$ (OH)16]2?+??[CO $_{3}^{2-}$ ?5H2O]2???, [Fe $^{\rm II}_{4}$ Fe $^{\rm III}_{2}$ (OH)12]2?+??[CO $_{3}^{2-}$ ?3H2O]2???, [Fe $^{\rm II}_{6}$ Fe $^{\rm III}_{2}$ (OH)16]2?+??[C2O $_{4}^{2-}$ ?4H2O]2??? and [Fe $^{\rm II}_{5}$ Fe $^{\rm III}_{2}$ (OH)14]2?+??[2HCOO????3H2O]2???. These formulae correspond to orders α, β and γ where cation distances are (2 × a 0), ( $\surd 3$ × a 0) or a mixture of both leading to (7 × a 0), where ratio x = {[FeIII]/[Fetotal]} = 1/4, 1/3 and 2/7, respectively. Anion distributions within interlayers are also devised and long-range orders determined accordingly.  相似文献   

9.
By using GaAs wafer as the saturable absorber, the laser-diode pumped passively Q-switched composite Nd:YVO \(_{4}\) laser has been successfully demonstrated. For this passively Q-switched operation, the average output power obtained is as high as 846 mW at the incident pump power of 5.31 W, while the pulse duration is as short as 14.5 ns. The largest single-pulse energy of 2.49 \(\upmu \) J and the highest peak power of 166 W are obtained. The GaAs saturable absorber with thickness of 400 \(\upmu \) m has shown more excellent laser performance comparing with 700 \(\upmu \) m thick GaAs.  相似文献   

10.
A passively Q-switched 1.06???m Nd:GdVO4 laser with a [100]-cut Cr4+:YAG saturable absorber was demonstrated. The output characteristics were investigated when the anisotropic transmission of Cr4+:YAG crystal and the incident pump power level were considered. The experimental results showed that it was feasible to generate laser with narrower pulse width (?? p ), higher pulse energy and peak power when the polarization direction of laser was parallel to the [001], [010], [ $00\overline{1}$ ], and [ $0\overline{1}0$ ] orientations of the Cr4+:YAG crystal. The different changes of ?? p as a function of incident pump power was observed due to the anisotropy of transmission of Cr4+:YAG and the different gain levels (pump power levels). If the Cr4+:YAG was fully bleached as a result of high cavity gain or due to the laser polarization direction was parallel to the [001], [010], [ $00\overline{1}$ ], and [ $0\overline{1}0$ ] orientations, ?? p was constant, otherwise ?? p decreased when the gain increased.  相似文献   

11.
The lifetime of the 331.3 keV 0 2 + state in100Zr has been measured at the gas-filled recoil separator for fission products JOSEF. By observing the delayed coincidences between theβ-particles populating the level and theE0 conversion electrons from its decay into the ground state, a half-life of 3.37±0.30 ns has been obtained. From the measured lifetime and the relative intensities of the 0 2 + →0 1 + and 0 2 + →2 1 + transitions, values of 0.493±0.015 for theE0 strength parameterρ, and of 16 single particle units forB(E2,2 1 + → 0 2 + ) have been deduced. The enhanced nature of theE0 transitions suggests mixing of the 0 1 + and 0 2 + states which may be estimated by comparing the experimentalB(E2) values for the 2 1 + →0 1 + and 2 1 + →0 2 + transitions with the predictions of the asymmetric VMI model.  相似文献   

12.
An investigation of inclusivepp→π?+? in terms of the covariant Boltzmann factor (BF) including the chemical potential μ indicates a) that the temperatureT increases less rapidly than expected from Stefan's law, b) that a scaling property holds for the fibreball velocity of π? secondaries, leading to a multiplicity law like ~E cm 1/2 at high energy, and c) that μπ is related to the quark mass: μπ=2m q ?m π the quark massm q determined by \(T_{\pi ^ - } \) at \(\bar pp\) threshold beingm q =3Tπ?330 MeV. Because ofthreshold effects \(T_{\bar p}< T_{\pi ^ - } \) , whereas \({{\mu _p } \mathord{\left/ {\vphantom {{\mu _p } {\mu _{\pi ^ - } }}} \right. \kern-0em} {\mu _{\pi ^ - } }} \simeq {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-0em} 2}\) as expected from the quark contents of \(\bar p\) and π. The antinuclei \(\bar d\) and \({{\bar t} \mathord{\left/ {\vphantom {{\bar t} {\overline {He^3 } }}} \right. \kern-0em} {\overline {He^3 } }}\) observed inpp events are formed by coalescence of \(\bar p\) and \(\bar n\) produced in thepp collision. Semi-empirical formulae are proposed to estimate multiplicities of π?, \(\bar p\) and antinuclei.  相似文献   

13.
A detailed $ \gamma$ spectroscopic decay study of two K isomers in 254No was performed. In addition to the previously reported $ \gamma$ lines two new transitions of E = 778 , 856keV could be attributed to the decay pattern of 254m1No ( T 1/2 = 275±7 ms). The population of an excited band built up on this isomer ( $\ensuremath K^{\pi} =8^{-}$ by the decay of 254m2No ( T 1/2 = 198±13 μs) could be proven by measuring delayed $ \gamma$ - $ \gamma$ coincidences between transitions stemming from the decay of both isomeric states. The energies of the band members could be established up to $\ensuremath I^{\pi} = 15^{-}$ . A spontaneous fission branch of (2.0±1.2)×10-4 was measured for 254m1No , an upper limit of $ \le$ 1.2×10-4 was estimated for 254m2No . These values demonstrate the high stability of multi-quasiparticle configurations against spontaneous fission. Evidence for an $ \alpha$ decay branch of 254m1No in the order of 1×10-4 was found.  相似文献   

14.
In composite models of quarks, leptons and weak bosons whereW-constituents are colored objects, color octet partners ofW ± andZ 0 are predicted. We study in detail the phenomenology of these particles. Independent of the specific model one expects a color octet isotriplet of vector bosons (W 8 ± ,Z 8 0 ) with mass in the range of 100–200 GeV, and a color octet isosinglet vector bosonV 8 0 with substantially larger mass, due to mixing with the gluon. Moreover, relatively light color octet excitations of the leptons appear, while the existence of “color exotic” partners of the quarks is model dependent. These particles decay mainly into a lepton (quark) and a gluon. We construct the couplings ofW 8 ± ,Z 8 0 andV 8 0 to ordinary and “color exotic” fermions. The signals of color octet weak bosons in low energy weak reactions are explored in detail. The production cross section ofW 8 ± (Z 8 0 ) in hadron-hadron collisions is calculated for \(0.54TeV \leqq \sqrt s \leqq 20TeV\) . Various decay modes of colored weak bosons are studied. The most prominent decay signatures ofW 8 ± andZ 8 0 are events of the type (l +-: charged lepton;j: hadronic jet; : missing transverse momentum). The present CERN \(p\bar p\) collider data on such events are discussed in the light ofW 8 ± andZ 8 0 decays. If colored weak bosons are not found with a mass less than ~250 GeV composite model building will be strongly restricted.  相似文献   

15.
The electron capture decays of133Ba (10.4 y) and139Ce (140 d) were investigated with high resolution Ge(Li) detectors. By x-ray — γ-ray coincidences values of the quantityP k ω k ? k for various transitions in the decay of133Ba and139Ce are obtained. The factor ω k ? k was measured independently by means ofK-conversion electron-K x-ray coincidences and was then used to determineP k , theK-capture probability. The independent measurement of the product ω k ? k , together with recent accurate values of ω k , provides a new method for the accurate calibration of semiconductor x-ray detectors. In the decay of139Ce, a value ofP k =0.78±0.03 is found (where the error represents twice the standard deviation) from whichQ ec =326 ?30 +70 keV to the139La ground-state is found by use of theory. In133Ba decay, values are found ofP k 1=0.72±0.04 for theEC transition to the 437 keV level in133Cs,P k 2=0.80±0.07 to the 384 keV level, and from an independent measurement, the ratioP k 1/P k 2=0.87±0.07. From these results the ground-state value ofQ ec =522 ?10 +20 keV is derived from theory for133Ba decay. The gamma spectrum of133Ba also was remeasured. From the present gamma intensities and previous conversion electron intensities, new values forK-shell conversion coefficients are obtained. Previously reported γ-rays at 35 and 391 keV are not confirmed.  相似文献   

16.
We report on the p T dependence of nuclear modification factors (R CP) for K S 0 , ??, ?? and the $\bar NK_S^0 $ ratios at mid-rapidity from Au+Au collisions at $\sqrt {s_{NN} } $ = 39, 11.5 and 7.7 GeV. At $\sqrt {s_{NN} } $ = 39 GeV, the R CP data show a baryon/meson separation at intermediate p T and a suppression for K S 0 for p T up to 4.5 GeV/c; the $\bar \Lambda K_S^0 $ shows baryon enhancement in the most central collisions. However, at $\sqrt {s_{NN} } $ = 11.5 and 7.7 GeV, R CP shows less baryon/meson separation and $\bar NK_S^0 $ shows almost no baryon enhancement. These observations indicate that the matter created in Au+Au collisions at $\sqrt {s_{NN} } $ = 11.5 or 7.7 GeV might be distinct from that created at $\sqrt {s_{NN} } $ = 39 GeV.  相似文献   

17.
The nonadiabaticity of E0 transitions from 0 2 + states and 2 1 + bands in 156Dy is examined within a phenomenological model that takes into account the mixing of K π = 0 1 + , 0 2 + , 0 3 + , 2 1 + states and 1+-bands. It is shown that the nonadiabaticity of E0 transitions is due primarily to the mixing of 0 2 + and 0 3 + bands.  相似文献   

18.
\(N\bar N\) annihilation into three pseudoscalar mesons especially πππ and \(K\bar K\pi \) are studied in the quark pair creation model or the3 P 0 model in which two \(q\bar q\) pairs are annihilated and two \(q\bar q\) pairs are created with quantum numbers of the vacuum or3 P 0. The correlations of two pions to form ?,f 2 and the resonance AX(1565) which is recently found by the ASTERIX group are taken into account. A proper treatment of the symmetry among the three pions in the final state shows that the \({}^{31}S_0 p\bar p\) annihilation into ?π is suppressed in agreement with the experiment. We calculate the cosθ distribution or the distribution of the Dalitz plot as the function of the angle between the direction of emission of one decay pion in the resonance centre of mass and the line of flight of the resonance. The interferences of π+ρ+, π?ρ+ and π0ρ0 in the isospin 0 channels and π±ρ? and π0 f 2 in the isospin 1 channel reproduce the peaks. The cos θ distribution for the P-wave \(p\bar p\) annihilation into πAX depends strongly on the size of the pion since the amplitude interfers with the π±ρ? amplitude which is sensitive to the size of the pion. The same model qualitatively explains the \(p\bar p\) annihilation into \(K\bar K\pi \) in whichK or \(\bar K\) and π are correlated to formK* \(\bar K\) or \(\bar K\) *K final states. We can qualitatively reproduce different patterns of the cos θ distribution for theK *+ andK *0.  相似文献   

19.
A search for double- $ \beta$ processes in 190Pt and 198Pt was realized with the help of ultra-low background HP Ge 468cm^3 $ \gamma$ spectrometer in the underground Gran Sasso National Laboratories of the INFN (Italy). After 1815 h of data taking with 42.5g platinum sample, T 1/2 limits on 2 $ \beta$ processes in 190Pt ( $ \varepsilon$ $ \beta^{+}_{}$ and 2 $ \varepsilon$ have been established on the level of 1014-1016y, 3 to 4 orders of magnitude higher than those known previously. In particular, a possible resonant double-electron capture in 190Pt was restricted on the level of 2.9×1016 y at 90% C.L. In addition, T 1/2 limit on 2 $ \beta^{-}_{}$ decay of 198Pt (2 $ \nu$ +0 $ \nu$ ) to the 2+ 1 excited level of 198Hg has been set at the first time: T 1/2 > 3.5×1018 y. The radiopurity level of the used platinum sample is reported.  相似文献   

20.
The gyromagnetic ratios of the 4 1 + , 6 1 + , and 2 2 + states in186W were measured relative to that of the 2 1 + level by means of the transient field implantation perturbedγ-ray angular distribution technique. The nuclei in the states of interest were Coulomb excited using a beam of 220-MeV63Cu projectiles and recoiled swiftly through a thin, polarized Fe foil. The present measurements yielded ratiosg(4 1 + )/g(2 1 + )=1.04±0.07,g(6 1 + )/g(2 1 + )=1.03 ±0.20 andg(2 2 + )/g(2 1 + )=0.63±0.13. The sizable disparity between the measuredg-factors of the ground- and excited-band is examined within the context of the interacting boson approximation model.  相似文献   

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