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1.
Spin effects in the weak two-body hadronic decays of the B c and B c * mesons into J/ψ and ρ(π) mesons are considered within the model of hard one-gluon exchange between quarks at high momentum transfers. It is shown that the polarization of the J/ψ meson in the decays of the B c * meson differs substantially from that in the decays of the B c * meson. The decay widths of the B c * meson differ significantly from the widths of the B c * meson.  相似文献   

2.
A laser induced charge transfer from Na(3p) to hydrogen-ions at different kinetic energies has been studied. An enhancement factor of about 90% in the production rate of Lyman-α radiation has been demonstrated to occur only with H+ and Na(3p) atoms reaction; no enhancement was observed with either H 2 + or H 3 + ions. Absolute cross-section for the production of Lyman-α radiation during the collision of H+, H 2 + and H 3 + ions and Na(3p) and Na(3s) atoms have been measured in the energy range 1–600eV. The charge exchange reactions involving hydrogen-ions and Na(3p) atoms created by two different methods have also been compared.  相似文献   

3.
For collision energies between 100 and 500 eV the collision induced dissociation of H 3 + colliding with H2, He and Kr gas targets was measured. We obtained total cross sections and angular distributions of the charged collision fragments for the main reaction channels. H 3 + +H2→H++2H2 and H 3 + +H2→H 2 + +H2+H. An analysis of the kinetics yields that the dissociation proceeds via vibrational-rotational excitation of H 3 + by mutually induced dipolmoments.  相似文献   

4.
The binding energies of neutron-rich strangeness S = ?1 hypernuclei are estimated in the chiral soliton approach using the bound state rigid oscillator version of the SU(3) quantization model. Additional binding of strange hypernuclei in comparison with nonstrange neutron-rich nuclei takes place at not large values of atomic (baryon) numbers, A = B ?? ??10. This effect becomes stronger with increasing isospin of nuclides, and for the ??nuclear variant?? of the model with rescaled Skyrme constant e. Binding energies of ?? 8 He and recently discovered ?? 6 H satisfactorily agree with data. Hypernuclei ?? 7 H, ?? 9 He are predicted to be bound stronger in comparison with their nonstrange analogues 7H, 9He; hypernuclei ?? 10 Li, ?? 11 LI, ?? 12 Be, ?? 13 Be, etc. are bound stronger in the nuclear variant of the model.  相似文献   

5.
Using quantum-chemical methods, we have studied the role played by water molecules W-A and W-B that are bound by hydrogen bonds to accessory bacteriochlorophyll molecules B A and B B in the process of primary charge separation in the reaction center of Rhodobacter Sphaeroides. We have found that the occurrence of a rotational mode of the W-A molecule at 32 cm?1 and/or its harmonics in stimulated emission of an electron donor P* and the dynamics of population of the states P+B A ? and P+H A ? may be related to the structural heterogeneity of the reaction center and the existence of a conformation in which the W-A molecule is predominantly involved in one hydrogen bond (with BA). Based on the calculated redox potentials B A and P, it has been shown that the appearance of the W-A molecule in the reaction center reduces the energy of the P+B A ? state by ??600 cm?1. This is somewhat smaller than the influence of the amino-acid residue TyrM210 (??870 cm?1) and correlates well with a substantial decrease in the electron transfer rate in mutant forms of reaction centers GM203L (which do not contain W-A molecules) and YM210F (in which TyrM210 is replaced with Phe). The data obtained allow us to suggest that rotation of the water molecule with a fixed position of its H atom that is involved in a hydrogen bond with the keto carbonyl group of B A is initiated due to the charge separation between the halves of special pair P and the formation of the state P A + P B ? . The large effect of this rotation on the kinetics of population of the states P+B A ? and P+H A ? after the excitation of P is quite consistent with its influence on the energy of the state P+B A ? .  相似文献   

6.
7.
The velocity distributions of H-H fragment pairs arising from dissociative collisions of 10keV H 2 + ions incident on H2, He, and Ar were measured using a flight-time-difference method. The H 2 + ions were produced in an electron impact ion source at two different electron energies, at 100eV and 18eV. The influence of the electron energy on the fragment velocity distributions is studied. Conclusions are drawn on the processes which lead to the formation of neutral fragment pairs. Electron capture into the repulsive b3 Σ u + state of H2 plays a dominant role.  相似文献   

8.
The kinetics of disorientation of B 80 4 centers is studied. The reorientation energy of the centers is determined to be ~1.5 eV. Based on the fact that this value is close to the energy of hexavacancy transition from the ground state to the first metastable state, it is concluded that the B 80 4 center is a ring hexavacancy. The reorientation mechanism is explained by the hexavacancy transition to the metastable state and, then, to a state with a new orientation.  相似文献   

9.
The energy-density components Θ 0 0 andT 0 0 of the canonical and of the metrical energy-momentum tensors Θ k i andT k i for a statical field of vector mesons have opposite signatures: Θ 0 0 =H=?T 0 0 =?L. From this property some relativistic and field-theoretical theorems can be deduced in an elementary way.  相似文献   

10.
The formation and optical properties of J aggregates of pseudoisocyanine iodide in solid films in the presence of cluster anionic derivatives of boron hydrides and carboranes (B10H 10 2- , B12H 12 2- , B20H 18 2- , [NiIV(1,2-B9C2H11)2]0, 1,2-B9C2H 12 - , [Co(1,2-B9C2H11)2]-, [Ni(1,2-B9C2H11)2]-, B10H8I 2 2- , [Sn(1,2-B9C2H11)]0) are studied. It is shown that the addition of anions B10H 10 2- or B10H8I 2 2- leads to an efficient formation of stable J aggregates. The addition of carborane complex of nickel [NiIV (1,2-B9C2H11)2]0 also leads to the formation of J aggregates, although less stable ones. Carborane complex of tin [SnII(1,2-B9C2H11)]0 facilitates the formation of a monomeric form of the dye. The remaining compounds yield no distinct pattern of formation of a certain monomeric or J-aggregated film structure. With the aid of the semiempirical AM1 method, the charge distributions in the cation of the dye and anionic derivatives of the boron hydrides are calculated. It is supposed that the bipolar distribution of a negative charge in the B10H 10 2- anion facilitates the formation of a J aggregate. By addition of salts of organic cations to a film of pseudoisocyanine-closo-hydrodecaborate (PCG), J aggregates with a narrow width of the J peak are obtained. The thermal decay of J aggregates in these films is studied. On the basis of the data obtained (the presence of an isosbestic point upon thermal decomposition of J aggregates and their reaggregation; the narrowing and increasing of the J absorption peak, as well as increasing of luminescence, upon dilution of a J-aggregated PCG film with organic cations; and the bipolar character of the electrostatic interaction of the B10H 10 2- anion with the dye), it is assumed that the J peak of pseudoisocyanine in the films studied corresponds to the absorption of a dimeric form of the dye.  相似文献   

11.
The optical absorption spectra of trivalent erbium in ScVO4 single crystals and ScPO4 powders with doping ratios between (500∶1) and (10∶1) have been obtained between 15,000 and 27,000 cm?1. From the positions of the Stark components of (Sc, Er)VO4 (100∶1) the five crystal field parametersB 0 2 ,B 0 4 ,B 0 6 ,B 4 4 andB 4 6 have been determined. Moreover the paramagnetic resonance of (Sc, Er)VO4 single crystals with doping ratios mentioned above have been examined. With these experimental results informations have been obtained about the doping with metal-ions of an essentially different ionic radius.  相似文献   

12.
A technique for mass-spectrometric investigation of the yield of positive ions produced by direct and electron-impact dissociative ionization of methane molecules is described, and respective experimental data are presented. Doubly charged C 2 + , CH 3 2+ , and CH 4 2+ ions, as well as singly charged D 2 + , CD 3 + , and CD 4 + ions, are detected in the mass spectrum of a methane molecule at electron energy U e = 90 eV for the first time. From ionization efficiency curves, the ionization energy of the parent molecule and the appearance energy of fragment ions are determined. The ionization energy of the CH4 molecule is found to be 12.62 ± 0.20 eV. Electron-molecular reactions that may take place when a low-energy electron beam interacts with a methane molecule are analyzed. The ionization process and the formation of methane molecule fragments are studied.  相似文献   

13.
In this note the Kepler-Coulomb problem in hyperbolic space H 2 2 : z 0 2 + z 1 2 ? z 2 2 ? z 3 2 = R 2 is discussed.  相似文献   

14.
Lifetimes and hfs coupling constants of some excited states of the 4d 9 5p configuration of Pd I have been determined in a level crossing experiment by observing the field dependence of the polarization of the fluorescence radiation in a magnetic field. From the halfwidths of the measured zero field level crossing signals one obtains the mean lifetimes of the following fine structure states:τ(3P 1 0 )=(7.46±0.32)nsec;τ(3 P 2 0 )=(6.9±0.76)nsecτ(3P 1 0 )=(4.99±0.35)nsec;τ(3 D 1 0 )=(4.89±0.40)nsecτ((3D 3 0 )=(6.99±0.49)nsec;τ(3 F 4 0 )=(7.09±0.46)nsec.Δm=2 crossing signals were detected in the3 P 1 0 ,3D 3 0 and3F 4 0 -states of the odd isotope105Pd. A detailed analysis of the experimental curves yields the hfs coupling constantsA andB of these states:A(3P 1 0 )=?(133±2) Mc/sec;B(3 P 1 0 )=(140±30) Mc/secA(3D 3 0 )=?(120±10) Mc/sec;B(3 D 3 0 )=?(660±100) Mc/secA(3F 4 0 )=?(87±2) Mc/sec;B(3 F 4 0 )=?(330±30) Mc/sec. A theoretical calculation of the hfs constants is given on the basis of reduced matrix elements. Within the limit of the errors these values agree with the experimental ones. The nuclear electric quadrupole moment deduced from the measuredB values isQ (105Pd)=(0.8±0.3)·10?24 cm2 (without corrections).  相似文献   

15.
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   

16.
Near infrared absorption measurements by Gross and Bron led to the suggestion that the threefold degeneracy of the localized vibration ofH i ? andD i ? centres in KI is completely lifted in KBr. Using thermal annealing procedures,H i ? -D i ? substitution and far infrared techniques we found that the lines at 794, 840, and 896 cm?1 cannot be interpreted as a splitting of the main line. Only the 794 cm?1 line can be correlated with the direct excitation of theH i ? oscillator. The absence of any splitting in this line (its halfwidth at 9 °K is only 1.5 cm?1) indicates that also in KBrH i ? centres have at most only slightly perturbedT d symmetry.  相似文献   

17.
The ΛΛ 6 He and Λ 9 Be hypernuclei are treated as the S=0, T=0 (for the former) and S=1/2, T=0 (for the latter) bound states of the three-cluster systems ΛΛα and Λαα, respectively. The cluster-reduction method is used to solve the s-wave differential Faddeev equations for these systems. On the basis of the MT I–III model, the ΛΛ interaction potential is specified in the form $V_{\Lambda \Lambda } = \frac{2}{3}V_{NN} $ . Phenomenological potentials are used to describe Λα and αα interactions. The binding energies of the ΛΛ 6 He and Λ 9 Be hypernuclei and the parameters of low-energy Λ-hyperon and α-particle scattering on a Λ 5 He hypernucleus are calculated. It is shown that the proposed ΛΛ interaction potential makes it possible to reproduce faithfully the binding energy of the ΛΛ 6 He hypernucleus and that scattering in the Λ Λ 5 He system is similar to neutron scattering on a deuteron.  相似文献   

18.
Using the Mössbauer technique electric hyperfine interactions of the first excited non-rotational states at 64 keV in157Gd and at 86.5 keV in155Gd have been determined in GdF3 and GdCl3· 6H2O. For the ratio of quadrupolmoments the ratiosQ 64 157 /Q g 157 =1.74±0.04,Q 86.5 155 /Q g 157 =?0.07 ± 0.21 andQ g 155 /Q g 157 =0.78 ± 0.06 were found. In addition isomer shifts were observed from which a ratio δ〈r2 64 157 /δ〈r2 86.5 155 =?2.6±0.15 can be inferred.  相似文献   

19.
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   

20.
The properties of the low-lying energy states for the 100Mo isotope is investigated within the framework of the proton-neutron interacting model IBM2.By considering the relative energy of the d proton boson to be diferent from that of the neutron boson and taking into account the dipole interacting among like-boson LπLπand LνLν,the low-lying energy spectrum is reproduced well.Particularly,the relative position of the energies for 2+1,0+2,2+2 and 4+1states shifted correctly fit the experimental data.The electromagnetic properties,including the key observable B(E2)reduced transition branching ratios and the E2 reduced matrix elements of the experimental data,are well described.Our calculations show possible shape coexistence in the 100Mo nucleus.  相似文献   

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