Secondary ion emission under the bombardment of Si by multiply charged Si q+ ions

The spectra of secondary ion emission under the bombardment of a B-doped Si target by multiply charged Si ^q+ ions (q = 1?C5) have been studied in the energy range of 1 to 10 keV per unit of charge. A multifold increase in the yield of secondary cluster Sk _n ⁺ ions, multiply charged Si ^q/+ ion (q = 1?C3), and H⁺, C⁺, B⁺, Si₂N⁺, Si₂O⁺ is observed as the charge of the multiply charged ions increases. The increase in the yield of secondary ions with increasing charge of the multiply charged-ion charge is most significant for ions with relatively high ionization potentials.     

E2/M1 Mixing ratios of 2+-2+-transitions in58Fe,74Ge and186Os

E2/M1 mixing ratios of 2⁺-2⁺-transitions in⁵⁸Fe,⁷⁴Ge and¹⁸⁶Os were determined by measuring the angular correlation of the 2-2-0γγ-cascades in these nuclei. The following values were obtained:⁵⁸Fe(863 keV):δ=+1.10±0.20;⁷⁴Ge(609keV):δ=?2.9±0.8 and¹⁸⁶Os(630keV):δ=?13 _?3.5 ^+5.5 . These results are compared with theoretical predictions.     

The 2+-2+ transition of 879 keV in160Dy investigated by electron-gamma directional correlation

e-γ directional correlation measurements of 2⁺(879 keV)2⁺(87 keV)0⁺ cascade in¹⁶⁰Dy have been made and the magnitude of electric monopole to quadrapole mixing ratio for 879 keV transition was found to beq _k =?0.03(10) for λ=0 (λ-according to Hager-Saltzer definition).     

g-factor of the 4 1 + rotational state of160Dy

By use of Ge-detectors of the OSIRIS-collaboration [1] in connection with the 12 detector IPAC apparatus of our laboratory [2] a precise measurement of theg-factor of the 4 ₁ ⁺ rotational state of¹⁶⁰Dy was performed. The directional correlations of the threeγ-γ cascades, 1003-197 keV, 1103-197 keV and 1115-197 keV, which are weakly populated in the decay of 72.3 d¹⁶⁰Tb were observed simultaneously. The integral rotations in the static hyperfine field of DyTb at 4.2 K were measured. Theg-factorg(4 ₁ ⁺ )=+0.350(20) was derived. By comparison with the magnetic splitting of the 2 ₁ ⁺ rotational state observed in the same environment by a Mössbauer experiment [3] the ratio of the twog-factors was derived as g(4 ₁ ⁺ )/g(2 ₁ ⁺ )=+ 0.91(5). For the high energy lines we derived from the measured directional correlations the E1/M2 mixing parameters: δ(1003 keV)=+0.005(4); δ(1103 keV)=?0.020(22), and δ(1115 keV)=+0.010(4)     

High-resolution study of E0 internal pair decay of excited 0+ states in 58,60,62Ni

The recently developed magnetic plus Si(Li)-Si(Li) sum-coincidence technique is employed to measure E0 internal-pair-formation (IPF) branching ratios of excited 0⁺ states in ^58,60,62Ni. The $\text{X(}\text{E}\text{0}\text{E}\text{2}\text{)}$ values are obtained for a new 0⁺₄ state in ⁶⁰Ni at 3588.0 keV, for the 0⁺₂ and 0⁺₃ states at 2942.3 keV and 3530.9 keV in ⁵⁸Ni, for the corresponding states at 2284.8 keV and 3318.3 keV in ⁶⁰Ni, and for the 0⁺₂ state in ⁶²Ni at 2048.4 keV. The results are combined with the available lifetimes of these states to extract the monopole strengths ?²(0⁺_i ? 0⁺₁). The results and the nature of the 0⁺ states are discussed.     

Die Zerstäubung von Kupfer durch Ne+-, Ar+-, Kr+- und Xe+-Ionen im Energiebereich von 75keV bis 1MeV

Using a 1,3 MeV Van de Graaff-accelerator the sputtering ratioS of polycristalline copper bombarded by normally incident Ne⁺-, Ar⁺-, Kr⁺-, and Xe⁺-ions was measured in the energy range from 75 keV to 1 MeV. In the case of Kr⁺-ions a broad, plateau-like maximum of the sputtering-curveS=f(E) was found at about 100 keV, for Xe⁺-ions a more pronounced maximum at about 125 keV. The results are discussed applying the theories ofGoldman-Simon, Pease, andMartynenko.     

Charge exchange cross sections for He+ incident on Cs

The total charge-exchange cross section, σ₊₀, for He⁺ incident on Cs vapor has been measured in the energy range 0.5 to 41 keV. The cross section falls from (1664 ± 100) × 10^?17 cm² at 1.4 keV to (224 ± 20) × 10^-17 cm² at 41 keV. These measurements are compared with previous measurements and with theoretical calculations of this cross section.     

Study of the excited states of119Sn by the decay of119g+m In

The decay of^119g+m In to the excited states of¹¹⁹Sn was investigated.¹¹⁹In was produced by the¹²⁰Sn(γ,p)¹¹⁹In reaction on an enriched SnO₂ target. The isomeric transition of 311.25 keV to the¹¹⁹In ground state was observed. In the beta decay of^119m In excited states at 23.9, 920.5, 921.4, 1089.0, 1187.9 and 1249.6keV in¹¹⁹Sn withJ ^π values of 3/2⁺, 3/2⁺, 5/2⁺, 5/2⁺, 3/2⁺ and 1/2⁺ respectively, are fed. In the decay of the¹¹⁹In ground state only the 7/2⁺ level in¹¹⁹Sn at 787.0 keV is fed.     

Multihadronic decays and partial widths of the J/Ψ (3100) resonance produced in e+e− annihilation at adone

The reactions e⁺e^?→ hadrons and e⁺e⁺e^?→e⁺e^? have been studied at the J/gY (3100) resonance). The relative weights of the topological cross sections for fixed charged multiplicity are σ₂=(32±5)%, σ₄=(49±8)%, σ₆=(18±3)%, and σ₈=(1±0.6)%. The average pion multiplicities are 〈n_ch〉=3.8±0.3 and 〈n_{π^o〉=3.1±0.8}. The decay widths are Γ_e=(4.6±0.8) keV, Γ_h=(59±24) keV, and Γ=(68±26) keV.     

The decay of121g+m In to levels in121Sn

The decay of¹²¹ g+m In to the excited states of¹²¹Sn was investigated.¹²¹In was produced by the¹²²Sn(γ,p)¹²¹In reaction on an enriched SnO₂ target. Strong indications of the isomeric transition of 321 keV to the¹²¹In ground state were found. In the beta decay of^121m In excited states at 60.1, 908.9, 1101.9, 1120.4, 1403.0, 2864.1, 3119.8 and 3228 keV in¹²¹Sn withJ ^π values 1/2⁺, 3/2(5/2)⁺, 3/2⁺, 5/2⁺, 5/2⁺ and 1/2⁺ or 3/2⁺ for the three levels around 3 MeV, are fed. In the decay of the¹²¹In ground state only the 7/2⁺ level in¹²¹Sn at 925.3 keV is fed.     

Excitation of the 1s 2- and 1s 4-levels of neon and argon by He+-impact at energies between 100 keV and 1000 keV

The excitation of the 1s ₂- and 1s ₄-levels of neon and argon by He⁺-impact has been studied in the energy range of 100 keV to 1000 keV. The total emission cross sections for the 1s ₂ levels show pronounced maxima at about 350 keV impact energy, whereas the cross sections for the 1s ₄ levels increase with decreasing energy.     

Nuclear structure of low-lying 0+ states in Ge and Se isotopes

The following meanlives of levels in⁷²Se have been measured using the recoildistance Doppler-shift method:Τ(2⁺, 862 keV)=3.1±0.6 ps,Τ(2⁺′, 1317 keV)=12.5±2.6 ps,Τ(4⁺, 1638 keV)=1.2±0.3 ps andΤ(6⁺, 2469 keV)≦0.7 ps. These meanlives yield sixB(E2) values which are discussed together with the known data of the depopulation of the excited 0⁺′ state at 937 keV. Systematics of 0⁺′ states in the mass region 70?A?100 show that the low excitation energy of the 0⁺′ states is correlated with subshell closures. This suggests that the previous interpretation of the 0⁺′ state in⁷²Se as a rotational band head is questionable.     

Enhancement of DD-Reaction yields from the Pd/PdO:Dx heterostructure by N+ and Ne+ ion beams using the GELIS setup

The results on DD-reaction yield enhancement from the Pd/PdO:D_x heterostructure by N⁺ and Ne⁺ ion beams in the energy range of 10–25 keV are presented. Neutron and proton fluxes were measured using a neutron detector based on He-3 counters and a CR-39 plastic track detector. Measurements showed significant DD-reaction yield enhancement effects. The screening potential for this heterostructure under these experimental conditions was determined as U _e = 897 eV.     

Study of low-lying states in151Eu via (n,n′γ) reaction

The levels of¹⁵¹Eu have been investigated in the (n,n′γ) reaction using nuclear reactor fast neutrons. The energies, intensities and angular distributions of theγ-rays have been measured with the Ge(Li) spectrometer. Four rotational bands with the following band heads and Nilsson configurations have been identified: ground state band, 5/2⁺ [402]; 21.5 keV, 7/2⁺[404]; 196.5 keV, 3/2⁺[411]; 260.5 keV, 5/2⁺[413]. The low spin states at 332.2 and 336.2 keV have been tentatively assigned to the l/2⁺[411] Nilsson orbital, but 522.8, 580.0 and 587.0 keV states to the 1/2⁺[420] Nilsson orbital. The negative parity levels at 353.7, 522.1 and probably 546.2 keV have been proposed basing on theh _11/2 proton state.     

Isobaric analogue states excited in the59Co(p, γ)60Ni reaction

The⁵⁹Co(p, γ)⁶⁰Ni reaction has been investigated in the proton energy regionE _p=1365–2150 keV. Decay schemes and branching ratios have been determined for ten resonances, five of which have been identified as possible analogues or fragments of analogues of the ground state (5⁺) and the 58.6 keV (2⁺), 277.1 keV (4⁺), 288.4 keV (3⁺), and 435.7 keV (5⁺) levels in⁶⁰Co. At eight of the resonances most of the decay seems to go via a group of states with an excitation energy of 5–9 MeV. The investigated analogue states give a Coulomb displacement energy of 9118±7 keV.     

Enhancement of DD-reaction yields from the Ti/TiO2:Dx heterostructure by H+ and N+ ion beams using the GELIS setup

The results on DD-reaction yield enhancement from the Ti/TiO₂:D_x heterostructure by H⁺ and N⁺ ion beams in the energy range of 10–25 keV are presented. Neutron and proton fluxes weremeasured using a neutron detector based onHe-3 counters and a CR-39 plastic track detector. Measurements showed significant DD-reaction yield enhancement effects. The screening potential for this heterostructure under these experimental conditions was determined as U _e = 796 eV.     

Study of low-lying 0+ excitations in228Th and232,234,236U in the (p,t) reaction

The (p, t) reaction was studied at 22 MeV proton energy using targets of^230,232Th and^234,236,238U. In²²⁸Th we observed in addition to the 832 keV first-excited 0⁺ level a second-excited 0⁺ level at 939 keV populated with 5% of the ground-state strength. A 0⁺ level proposed recently in²³²U at 927 keV was not observed in the (p, t) reaction, with an upper limit for its excitation of 0.2% of the ground-state strength. In²³⁴U a level at 1045 keV, assigned in the literature as second-excited 0⁺ level, is weakly populated in the (p, t) reaction but does not show the angular distribution characteristic for single-stepL=0 transfer. In²³⁶U we observed a level at 1036 keV with an angular distribution suggesting that it might be a doublet composed of a known 3^? level and a new 0⁺ level. The properties of the first two excited 0⁺ bands in²²⁸Th,²³²U and²³⁴U are compared and discussed.     

稀土离子Ho+,Ce+,La+与H2碰撞的单电子俘获截面测量

在复旦大学加速器实验室的３０ｋｅＶ同位素分离器上，使用新近建立的一套用于单价离子与气体分子碰撞的单电子俘获截面测量装置，测量了５—３０ｋｅＶ Ho⁺,Ce⁺,La⁺与H₂碰撞的单电子俘获截面．实验发现中空型离子源的阳极电压的变化对于稀土离子的亚稳态比例有一定影响，同时造成了单电子俘获截面的很大变化，而阳极电压对Ａｒ⁺的影响很小．还对实验结果进行了分析 关键词：     

Das Positronenspektrum von22Na und die Ruhemasse des Neutrinos aus dem β+-Zerfall

Theβ ⁺ spectrum of²²Na has been measured with the Heidelberg (π/2) √13 iron-freeβ-ray spectrometer. Particular attention was paid to the upper end of the continuum. The maximum energy was found to beE _max=(545.7 ±0.5) keV. The rest mass of the neutrino connected withβ ⁺ decay was found to be zero with an upper limit of 4.1 keV (67 per cent confidence).     

Mössbauer studies and nuclear quadrupole moments of186, 188, 189, 190 Os

Mössbauer transmission experiments with the 137, 155, 69 and 187 keV gamma rays of^{186, 188, 189, 190}Os, respectively, yielded the electric quadrupole splitting of these gamma resonance lines in OsO₂ and OsP₂. From the results the following ratios of quadrupole moments were derived:Q ₂ ⁺(¹⁸⁶Os, 137 keV):Q ₂ ⁺(¹⁸⁸Os, 155keV):Q ₂ ⁺(¹⁹⁰Os, 187 keV):Q _3/2 ^?(¹⁸⁹Os, g.s.)=(+1.100±0.020): 1.0:(+0.863±0.051): (?0.586±0.011) andQ _5/2 ^?(¹⁸⁹Os, 69 keV)/Q _3/2 ^?(¹⁸⁹Os, g.s.)=?0.735 ±0.012. The ratios for^{180, 188, 190}Os are, within their limits of error, in agreement with the expectation of the rotational model, indicating that the pairing-plusquadrupole model calculations of Kumar and Baranger predict too rapid a transition form rotational to vibrational nuclei. Applying this argument to¹⁸⁶Os in particular and using the measured ratios, one obtains a set of values for the quadrupole moments themselves, namelyQ ₂ ⁺ (¹⁸⁶Os)=?(1.50 ± 0.10)b,Q ₂ ⁺(¹⁸⁸Os)=?(1.36± 0.09) b,Q ₂ ⁺ (¹⁹⁰Os)=?(1.18 ± 0.08) b,Q _3/2 ^?(¹⁸⁹Os)=+ (0.80 ± 0.06) b, andQ _5/2 ^? (¹⁸⁹Os)=? (0.59 ± 0.05) b. For the electric field gradient at Os nuclei in Re metal a value ofV _zz=?(3.3 ± 0.6) · 10¹⁷ V/cm² was found. A measurement with a magnetically split source yielded δ=+ 0.685 ± 0.025 for theE2/M1 mixing parameter of the 69 keV transition of¹⁸⁹Os,g _5/2 ^?/g _3/2 ^?=0.895 ± 0.006 for the ratio of theg-factors of the 69 keV state and the groundstate, andH _i=?(1135 ± 20) kOe for the hyperfine field at Os nuclei in an iron matrix.