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1.
The level schemes of 98, 99Ru were studied with the reactions 98Mo(α, 3nγ) and 98Mo(α, 4nγ) at Eα = 35 to 55 MeV, using a large variety of in-beam γ-ray detection techniques and conversion-electron measurements. A search for the 3? state was carried out with the reaction 98Ru(p, p′). The ground-state band of 98Ru was excited up to Jπ = (12)+ and a negative-parity band up to (15)?. New levels in 98Ru were found at Ex = 2285 (Jπ = 4+), 2435 (Jπ = (3?, 4+)), 2671, 3540, 4224, 4847, 4915 (Jπ = (12)+), 4989 (Jπ = (12+)), 5521 (Jπ = (13)?), 5889, 6591 (Jπ = (15)?), and 7621 keV. New unambiguous spin and parity assignments were made for the levels at Ex = 2014 and 3852 keV, as Jπ = 3+ and 9?, respectively. New levels in 99Ru were found at Ex = 1976, 2021 (Jπ = (152+)), 2393, 2401 (Jπ = (172+)), 2875 (π = (+)), 3037, 3201 (Jπ = (232)?), 3460 (J = (172)), 3484 (Jπ = (212+)), 3985, 4224 (Jπ = (272?)), and 5359 keV. The 1070 keV, Jπ = 112? level in 99Ru has a half-life of 2.8 ns. A strongly excited negative-parity band is built on this level. A positive-parity band based on the ground state was excited up to Jπ = (212+). The level schemes are well reproduced by the interacting boson model in the vibrational limit.  相似文献   

2.
Gamma rays following the β? decay of 30Al have been investigated with a Ge(Li) detector. The 30A1 sources were produced by fast neutron bombardment of an enriched 30Si sample. Evidence for two previously unreported β? branches has been deduced. The existence of allowed β? transitions to Jπ = 2+and 3+ states and to the Jπ = 4+ level at 5.95 MeV determines Jπ = 3 + for the 30Al ground state (T12 = 3.56 ± 0.02 s). These results are compared to a recent shell-model calculation.  相似文献   

3.
A new T = 0 level of 18F, Ex = 4848.3 ± 0.5 keV, has been studied using the 6Li(16O, αγ)18F reaction. The γ-decay by a 65 ± 4 % branch to the 1121 keV (5+) level and 35 ± 4 % to the 3791 keV (3?) level has been observed and a lifetime limit τ > 2 ps has been given. A tentative assignment Jπ = 5? is proposed which is supported by the α-γ angular correlation measurements. The possible structure of the new level and reasons why it had not been observed in past experiments are discussed.  相似文献   

4.
The analysing power of the 7Li(d, n0) 8Be reaction for vector and tensor polarization of an 800 keV deuteron beam, as well as the relative cross section for the unpolarized beam were measured at 7 to 9 angles between 0° and 160°, using a thick target. Analysis in terms of (l, s, Jπ) matrix elements shows that two intermediate states with Jπ = 32+ and Jπ = 52? present, strongly interfering with each other. Assignments to known 9Be levels and to threshold resonances as suggested by Hackenbroich and Seligman are briefly discussed. The magnitude of the vector analysing power makes the reaction interesting as a monitor for the vector polarization of low-energy deuteron beams.  相似文献   

5.
Levels in 208At were populated in the 209Bi(α, 5n) reaction, and the subsequent radiation was studied using γ-spectroscopic methods including γ-ray excitation function and angular distribution, γγ(t) coincidence and γt measurements, as well as measurements of conversion electrons. The excited spectrum of 208At is found to consist of two almost disconnected parts which are proposed to originate from seniority-three proton and neutron cascades. Two isometric states are observed. A T12 = 45 ± 2 ns state at 1090 keV is proposed to have the main configuration πh92j20+vi?1132j?20+ and Jπ = 10?. A high-spin isomer with T12 = 1.5 ± 0.2 μs at 2276 keV is assigned to be the π(h292i132)292+vf?152j?20+Jπ = 16? state. Shell-model arguments are used to assign configurations to most of the observed levels. Transition rates are discussed.  相似文献   

6.
The time dependence of microwave absorption was measured for the J = 2-1 and J = 3-2 transitions of OCS under on- and off-resonant conditions utilizing Stark and source modulation, respectively. The two effective pressure parameters obtained under the two conditions, which correspond to (T2?1 + T1?1)4πP and (2πT2P)?1, respectively, according to the Bloch equation, are different beyond experimental error; the difference (T2?1 ? T1?1)2πP is 0.94 ± 0.38 (2.5σ) MHz/Torr for J = 2?1. This difference was also determined to be 1.19 ± 0.30 MHz/Torr from the dependence of the nutation frequency on the microwave power.  相似文献   

7.
Lifetime and g-factor measurements have been made with pulsed beam-γ time-differential techniques using the 89Y(α, 2n)91Nb and 88Sr(α, n)91Zr reactions. A mean lifetime τ = 14.4 ± 0.5 nsec and a g-factor of 1.26 ± 0.04 were obtained for the 132? 1985 keV level in 91Nb and τ = 41.9 ± 1.2 nsec and g = 0.70 ± 0.01 were obtained for the 152? 2288 keV level in 91Zr. These results are compared to theoretical calculations for g92)2p12) and g92)(πp12)(vd52) configurations in 91Nb and 91Zr, respectively.  相似文献   

8.
The spectrum seen in single neutron pickup leading to the doubly odd nucleus 84Rb is remarkably clean, with only five levels populated by l = 4 and six by l = 1 transitions. A simple 2J+1 weighting for the l = 4 data, combined with previous information on 84Rb, allowed the Jπ = 2?–7? states of the (vg92?3? πf52?3) multiplet to be identified. These data are used to determine the two-hole πf52?1-vg92? interaction matrix elements.  相似文献   

9.
A complete set of conventional γ-ray spectroscopic techniques has been applied to investigate the level structure of 156Gd. A total of twenty-five new levels has been established; unambiguous spin assignments could be given for twelve of them on the basis of angular distributions and conversion electron measurements. The proposed level scheme contains 49 levels, which can be ordered in seven rotational bands. The ground-state band was excited up to Jπ = 14+, the β-band up to 10+, the γ-band up to (11+), the second Kπ = 0+ band tentatively up to (10+), the Kπ = 4+ band up to (8+). Two negative-parity bands, one with even spins and one with odd spins, were excited to Jπ = (12?) and (13?). An isomeric state was established with T12 = 1.3 μs, Jπ = 7?, Ex = 2137.7 keV. The properties of the Kπ = 4+ band and the isomeric state can be well explained by two-quasiparticle configurations. The negative-parity bands are interpreted as aligned octupole bands. Positive and negative-parity bands have been calculated in terms of the IBA model. Good agreement with the experimental results is obtained.  相似文献   

10.
The reaction 12C(7Li, t)16O has been studied at E(7Li) = 34 MeV with the LASL tandem accelerator and QDDD magnetic spectrometer. Angular distributions to levels with Ex < 11 MeV have been obtained from 0° to 90°, including 0°. The results have been analyzed with finite-range distorted-wave Born approximation theory. The α-particle spectroscopic factors and reduced widths obtained are compared with those calculated with group theory (SU(3)) and other models. The analysis of data for the 7.1 and 9.6 MeV Jπ = 1? levels, which are of great importance in stellar helium buring, yields a ratio, R, of dimensionless reduced α-widths θ2a(7.1 MeV)θ2a(9.6 MeV) = 0.35b ± 0.13. The observed line width of the 9.6 MeV level (Γc.m. = 390 ± 60 keV) is less than the accepted value (Γc.m. = 510 ± 60 keV) and implies θ2a(9.6 MeV) ≈ 0.6. These results as well as data for the 6.92 MeV Jπ = 2+ and 10.35 MeV Jπ = 4+ “α-cluster” states indicate 0.09 < θ2a(7.1 MeV) < 0.33 with a mean value θ2a(7.1 MeV) = 0.14 ± 0.04. The implication for stellar helium burning is discussed.  相似文献   

11.
The 68Zn(d, α)66Cu reaction populating low-lying states in 66Cu has been studied at θlab = 4° using deuteron beams in the energy range 9.0 to 10.5 MeV. Tensor analyzing powers were calculated and natural- or unnatural-parity assignments were made for thirteen states in 66Cu. By combining these results with existing limits unambiguous Jπ assignments of 2+, 2+, 2+ and 1+ have been made for the levels at 186, 465, 822 and 1344 keV respectively. The previous tentative assignments to seven other levels have been confirmed while that for the 1247 keV level has been shown to be incorrect. The identification of the quartet of levels based on the π(P32)v(f52) configuration has been confirmed.  相似文献   

12.
The β+ decay of 45V (Jπ, T=72?, 12) has been observed. The half-life was found to be 539 ± 18 ms; in addition to the superallowed transition to the mirror state (45Ti ground state), it exhibits a (4.3 ± 1.5)% allowed branch to the 52? state at 40.1 keV in 45Ti. Decay data for the complete f72 shell series of mirror nuclei are presented.  相似文献   

13.
J/ψ production at 40 GeV/c by π±, K±, p and p incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π? have been measured to be (for xF > 0) σ(π?) : σ(π+) : σ(p) : σ(p) = 1 : (0.78 ± 0.09) : (0.83 ± 0.35) : (0.07 ± 0.04). The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. MJ2/ψ/s=0.13).  相似文献   

14.
Low and high energy spectra from thermal neutron capture in 237Np have been studied over the energy ranges 25 to 650 keV and 2600 to 5500 keV. Primary transitions from neutron capture in four resonances have been observed between about 4800 and 5400 keV. Using 12 MeV deuterons, (d, p) spectra at three angles have been observed with a magnetic spectrograph. A nuclear level scheme for 238Np has been constructed by combining the results of the above measurements with previous data from a study of the 242mAm α-decay. The Nilsson model has been used to interpret the level structure. Including results from the previous α-decay study, nine rotational bands can be assigned. The Nilsson configurations (Kπ [Nn3ΛΣ]) and band-head energies are: 2+π[642↑]?ν[631↓], 0.0 keV; 3+π[642↑]+ν[631↓], 86.6 keV; 3?π[523↓]+ν[631↓], 136.0 keV; 2?π[523↓]?ν[631↓], 182.8 keV; 5+π[642↑]+ν[622↑], 278.1 keV; 0+π[642↑]?ν[622↑], 332.5 keV; 5?π[523↓]+ν[622↑], 342.6 keV; 0?π[523↓]?ν[622↑], 286.0 keV; 6?π[642↑]+ν[743↑], 301 keV. The measured (d, p) reaction cross sections are compared with theoretical calculations based on these assignments. The Gallagher-Moszkowski rule is found to be valid in the four cases where we have observed both parallel and antiparallel coupled bands with K+ = Ωpn and K? = |Ωpp|. The lowest levels of the two K = 0 bands have spin I = 1; Newby odd-even shifts can be determined in both cases.  相似文献   

15.
The nuclear structure of 5125Mn was studied by γ-ray spectroscopy in the 54Fe(p, α)51 Mn reaction (Ep = 9.0–13.2 MeV) and the 14N+39K, 16O+40Ca and 14N+40Ca fusion-evaporation reactions (Ebeam = 36 MeV). In the 54Fe(p, αγ)51Mn reaction γ-rays were detected in coincidence with α-particles emitted near 180°; mean lifetimes and γ-ray mixing and branching ratios were deduced from Doppler shift attenuation and α-γ angular correlation measurements, respectively. Definite spin assignments are: 237 and 2416 keV, Jπ = 72?; 1140 keV, 92?; 1488 keV, 112?; 1825 and 2140 keV, 32?. The results for other states below 3 MeV are consistent with the existence of rotational bands (/kh2/2/OI/t~ 95 keV) built on the (32+) 1817 keV and 12+ 2276 keV hole states. The various measurements together with an earlier value for the lifetime of the first-excited state determine unambiguously the B(M1) and B(E2) values for all of the decay branches of the 72?, 92? and 112? lowest three excited states. From the γ-singles and γ-γ coincidence observations with fusion-evaporation reactions, the yrast cascade proceeds through these three states and higher states at 2957, 3250,3680 and 4139 keV which are suggested to have Jπ = 132?, 152?,152? and 192?, respectively. The various experimental results for the 52? → (192?) yrast states are in good overall agreement with shell-model calculations in the (f721 space.  相似文献   

16.
An investigation of the γ-decay of the 1g92 analogue state in 59Cu has been performed using the 58Ni(p, γ)59Cu reaction. The (p, γ) excitation function has been taken in the range Ep = 3450–3650 keV. The decay schemes of the (p, γ) resonances at Ep = 3483, 3532 and 3547 keV, measured with Ge(Li) detectors, lead to eight new levels in 59Cu with excitation energies between 1.8 and 4.7 MeV and to spin assignments of several states. The spins of the first two resonances are found to be (12, 32) and (52). The spin of the Ep = 3547 keV resonan is, from angular distributions, uniquely determined to be Jπ = 92+ and this state is found to be the unfragmented analogue state of the E1 = 3.062 MeV, Jπ = 92+ parent state in 59Ni. The measured complete decay scheme of this resonance shows that its isovector M1 decay is in disagreement with all existing theoretical predictions.  相似文献   

17.
Using the 52Cr(t, p)54Cr reaction at a bombarding energy of 15 MeV, excitation energies have been measured for 30 levels up to Ex = 5.583 MeV in 54Cr. Angular distributions were obtained for all but one of these levels; these have been compared with distorted-wave Born approximation (DWBA) calculations to determine the L-transfer (and hence Jπ). The measured cross sections have been compared to the predictions of DWBA calculations that use two-neutron transfer amplitudes from a shell-model calculation with the active neutrons restricted to the (2p32, If52, 2p12) orbitals.  相似文献   

18.
Using the OSIRIS on-line isotope separator facility, the decays of 130Sn and 130, 132Sb have been studied. On the basis of singles γ and γ-γ coincidence Ge(Li) spectra and conversion electron Si(Li) measurements, level schemes for 130Sb, 130Te and 132Te have been constructed. The corresponding half-lives have been measured using multiscaling technique. The 3.8 min ground state of 130Sn populates only positive parity states in the πν?3 nucleus 130Sb: the energetically lowest 5+ state with the (π1g72, ν2d32) configuration assignment; the T12 = 3.6 ± 0.3 ns 4+ state at 70.0 keV; the 2+ state at 262.5 keV; the (0, 1)+ state at 697.2 keV; the 3+ state at 813.1 keV and the 1+ state at 1042.3 keV excitation energy. A 1.7 min isomeric state in 130Sn, with the tentative spin assignment (7?), populates several odd parity levels in 130Sb. These arise from the (π1g72, ν1h112-1) and/or (π2d52, ν1h112-1) configurations and are located 84.7 keV (6?), 144.9 keV (7?), 688.5 keV and 1044.0 keV above the 40 min 8? β- decaying state. No transitions between odd and even parity states have been observed.The most important excited states in 130Te found in the β? decay of the 6.6 min 130Sb 5+ state are: 839.4 keV, 2+; 1632.8 keV, 4+; 1815.1 keV, 6+; 2100.8 keV, 5?.Levels in the π2ν?2 nucleus 132Te were observed in the β? decays of the 2.8 min 132Sb (4+) and the 4.2 min 132Sb (8?) states. Unique spin and parity assignments have been given to the following states: 973.9 keV, 2+; 1670.7 keV, 4+; 1774.1 keV, 6+; 1924.7 keV, 7?; 2053.0 keV, 5?.  相似文献   

19.
The probability distribution calculated for the decay sequence 12ΛB(g.s.) → 12C1π? → αααπ? passing through the (JPN) = (2+, 1) intermediate state 12C1 (16.11 MeV) is cast in a symmetrical form and used to calculate the likelihood for J = 1 relative to J = 2 for12ΛB(g.s.) on the basis of the 85 examples available for this decay process. This procedure has optimum sensitivity, is free from the uncertainties of the comparisons previously made using only projected angular distributions, and strongly indicates that JP = 1? holds for 12ΛB(g.s.). An appendix points out that all the data for the decay sequence passing through the (JPN, T) = (1+, 0) level of 12C1 is well fitted for J = 1 if the J = 1 → Jn = 1 transition amplitude as1 takes a value in the range as1/s = 0.08 to 0.09.  相似文献   

20.
A high-accuracy investigation of the level scheme of 47V has been performed using the 46Ti(p, γ)47V reaction. The γ-decay schemes of the strong (p, γ) resonances at Ep = 1546, 1549, 1565 and 1572 keV lead to 17 new energy levels in 47V with excitation energies between 2.7 and 5.1 MeV. From the (p,γ) angular distributions mixing ratios of the primary γ-transitions and Jπ values of the resonances and of many states populated in the γ-decay have been determined. The total width of the Ep = 1549, 1565 and 1572 keV resonances for γ-decay are found to be Γγ = 0.12, 0.15 and 0.03 eV, respectively. The Q-value of the 46Ti(p,γ)47V reaction is found to be 5168.6 keV. The two resonances at Ep = 1549 and 1565 keV, which have Jπ = 32?, are interpreted as fine structure components of the analogue state of the E1 = 2.545 MeV Jπ = 32? level in 47Ti while the (72) resonance at Ep = 1546 keV might correspond to the E1 = 2.615 MeV72? parent state in 47Ti. The analogue-antianalogue M1 transition strength of the split 32? analogue state is 0.01 single-particle units and fits well into our systematics of IAS → AIAS transitions in fp-shell nuclei.  相似文献   

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