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1.
Excitation functions of the capture reaction 12C(p, γ0)13N have been obtained at θγ = 0° and 90° and Ep = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in 13N is included in the analysis in addition to the two well-known resonances in this beam energy range and 1699 . The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C2S(l = 1) = 0.49 ± 0.15 has been deduced for the ground state in 13N. Excitation functions for the reaction have been obtained at θγ = 0° and 90° and Ep = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the unbound state. Above Ep = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below Ep = 1 MeV, i.e., Ep → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at , a spectroscopic factor of C2S(l = 0) = 1.02 ± 0.15 has been found for the unbound state. A search for direct capture transitions to the and unbound states resulted in upper limits of C2S(l = 1) ≦ 0.5 and C2S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the 12C(p, γ0)13N reaction also is discussed. 相似文献
2.
J. Heintze G. Heinzelmann P. Igo-Kemenes R. Mundhenke H. Rieseberg V. Roberto B. Schürlein H. W. Siebert V. Soergel H. Stelzer K. -P. Streit A. H. Walenta 《Physics letters. [Part B]》1977,70(4):482-486
Partial branching ratios have been measured in six lepton momentum bins between 120 and 180 MeV/c. From these, six relations between the form factor slopes λ+ and λ0 have been derived. Using the world average value λ+ = 0.029 ± 0.003 and combining the six partial results on λ0, we obtain λ0 = 0.019 ± 0.010. This value is in agreement with the Callan-Treiman relation and other predictions. Together with recent K30 results, it supports the rule. The agreement of our result with the value of λ0 obtained from Kμ3 Dalitz-plot studies supports muon-electron universality. 相似文献
3.
Prasad Varanasi 《Journal of Quantitative Spectroscopy & Radiative Transfer》1975,15(2):191-196
Self-broadened, air-broadened and CO2-broadened half-widths of lines R(0) through R(0) in the CO fundamental have been measured at 100°K (self-broadening only), 200°K, 250°K and 300°K using the Ladenburg-Reiche curve-of-growth. The relation , which we found previously for the nitrogen-broadened half-widths of R(0), R(8) and R(16), is shown to be valid for all of the line widths measured in the present study. 相似文献
4.
From the angular distributions of γ-rays emitted by oriented 129gTe and 129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of 129I at 487.4 keV , 696.0 keV , 729.6 keV , 768.9 keV , 1050.4 keV and 1111.8 keV . In addition, E2/M1 amplitude ratios for the following 129I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076+0.037?0.148); δ(487.4) = 0.50+0.17?0.10 or δ? = 0.35+0.15?0.09; δ(556.7) = 0.06±0.02 or δ? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ?1 =0.20±0.03 if ; δ(1022.6) = ?(0.02 ±0.02) or δ?1 = ?(0.23±0.02); ; δ(1111.8) = 0.06±0.05 or δ?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes as a possible spin assignment for the 559.6 keV level, so that no level is fed in the decay from 129Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model. 相似文献
5.
A forward dispersion relation cannot be applied to charged particle scattering amplitudes unless the influence of the Coulomb interaction is explicitly considered. Earlier studies have shown how Coulomb effects can be taken into account when direct (s-channel or bound-state) poles are investigated. In this paper we extend the Coulomb modification to include I = 0 exchange (u-channel) processes as well. We then apply a forward dispersion relation to empirical d + α, p + d and n + d elastic scattering amplitudes which contain both direct and exchange poles with and without Coulomb effects. We obtain detailed and model-independent information on the following vertices: 6Li-α-d (S- and D-state) 4He-d-d, 3He-d-p, 3H-d-n and d-p-n. From the coupling constants we calculate the asymptotic normalization (spectroscopic factors) C21 of the corresponding cluster wave functions, which become: , , C20(α, dd) < 2, , . 相似文献
6.
Cyclotron resonance of electron and holes have been optically detected at 70 GHz and at 1.8 K in n-type CdTe. The bare effective masses, in unit of the free electron mass, are found to be: , , , and , , for H // <111>. The Luttinger valence band parameters deduced from these measurements are: γ1 = 5.3 ± 0.5, γ2 = 1.7 ± 0.3 and γ3 = 2.0 ± 0.3, in fair agreement with the calculations of Lawaetz. 相似文献
7.
We study the small λ behavior of the ground state energy, E(λ), of the Hamiltonian . In particular, if V(x) ~ ?ax?2 at infinity and if 69-1, we prove that . 相似文献
8.
Using Brillouin scattering, the elastic and elasto-optic constants of ammonium perchlorate have been measured at room temperature. The polarized Brillouin scattering spectra yielded the nine elastic constants (in the units of as follows: C11 = 2.51, C22 = 2.46, C33 = 3.15, C44 = 0.66, C55 = 0.47, C66 = l.03, C12 = 1.63, C23 = 1.15, C23 = 0.76; as well as the absolute value of nine elasto-optic constants. In the light of these results, some thermodynamic properties of the crystal are discussed. 相似文献
9.
Hyperfine structure of the (0, 0, 1) - (1, 0, 1) transition of methanol has been investigated by beam absorption and of the (J, 1, 3?) → (J, 1, 3+) transitions for J = 2, 3, and 6 by beam-maser spectroscopy. The best-fit results for the spin-rotation and spin-spin coupling constants and , respectively, are in kHz1: , , , , , and (. 相似文献
10.
M. Villedieu N. Devismes A.M. de Goër 《Journal of Physics and Chemistry of Solids》1977,38(9):1063-1070
The effect of γ irradiation at 300 K on the concentrations of vanadium ions V3+, V4+ and V2+ in Al2O3 has been studied quantitatively, using three techniques: optical absorption (V3+), low temperature thermal conductivity measurements (V4+) and EPR (V2+). Several single crystals of Al2O3 doped with vanadium in a large range of concentration have been measured. The evolution of the respective concentrations by γ irradiation as a function of the total vanadium content C is quite different in the two regions and C larger than this value. A consistent analysis of the results has nevertheless been achieved, leading to the determination of the absolute concentrations of the three ions in the as-received and γ irradiated states for all samples with (room temperature annealing is observed above this value). The concentrations of V4+ and V2+ ions are always small, but V4+ ions are more stable: they are present in the as-received state at a level of 1% of the total concentration and a maximum value of is observed in the γ irradiated state; on the other hand there are less than 4.7 × 1015V2+ ions per cm3 in the as-received state and the maximum value is only . Charge transfer between V ions only is not sufficient to explain the experimental results and other defects must be involved in the γ irradiation effect. 相似文献
11.
12.
Levels of 33S for Ex < 5 MeV have been studied with the 30Si(α, nγ)33S reaction at bombarding energies of Eα = 7.5 and 10.2 MeV. Neutron-gamma angular correlation experiments lead to three unambiguous spin and parity assignments: . The measured branching and mixing ratios yield transition strengths for dipole and quadrupole transitions. 相似文献
13.
The 20Ne(p, γ)21Na capture reaction has been studied in the energy range Ep = 0.37–2.10 MeV. Direct-capture transitions to the states have been found with spectroscopic factors of C2S(1d) = 0.77±0.13 and C2S(2s) = 0.90±0.12, respectively. The high-energy tail of the 2425 keV state, bound by 7 keV against proton decay, has also been observed in the above energy range as a subthreshold resonance. The excitation function for this tail is consistent with a single-level Breit-Wigner shape for a γ-width of Γγ = 0.31±0.07 eV at Ex = 2425 keV. The extrapolation of these data to stellar energies gives an astrophysical S-factor of S(0) = 3500 keV · b. Two new resonances at Ep = 384±5 and 417± 5 keV have been observed with strengths of ωγ = 0.11±0.02 and 0.06±0.01 meV, corresponding to the known states at and 2829 keV (presumably ), respectively. For the known Ep = 1830 keV resonance, a strength of ωγ = 1.0± 0.3 eV and a total width of Γ = 180± 15 keV were found. Branching ratios as well as transition strengths have been obtained for these three states. The Q-value for the 20Ne(p, γ)21Na reaction (Q = 2432.3 ± 0.5 keV) as well as excitation energies for many low-lying states in 21Na have been measured. No evidence was found for the existence of the state reported at Ex = 4308±4 keV.In the case of 22Ne(p, γ)23Na, direct-capture transitions to six final bound states have been observed revealing sizeable spectroscopic factors for these states. The astrophysical S-factor extrapolated from these data to stellar energies, is S(0) = 67 ± 12 keV · b.The astrophysical as well as the nuclear structure aspects of the present results are discussed. 相似文献
14.
Ali Tatli 《Journal of Physics and Chemistry of Solids》1985,46(9):1015-1018
The theories of Kyame [1] and Koga et al. [2] on stress wave propagation in piezoelectric media are critically studied and compared with each other. Solutions of the modified Christoffel's equations predicted by each theory for piezoelectric crystals in class 3m are derived. The velocities of ultrasonic waves propagated through a gem quality uvite specimen in particular directions were measured at 293 K using the pulse-echo overlap method. All of the independent zero-field elastic moduli were calculated from the measured wave velocities and compared with the available data in the literature. The values of the elastic constants in 1012 were found to be C11 = 3.016 ± 0.2% C66 = 1.028 ± 0.3% C33 = 1.698 ± 0.2% C13 = 0.47 ± 3% C44 = 0.655 ± 0.3% c14 = ?0.089 ± 6%. The calculated bulk modulus, shear modulus and Poisson's ratio, using the Voigt-Reuss-Hill (VRH) approximation, are KH = 1.226 × 1012, GH = 0.826 × 1012 and σH = 0.224. The Debye temperature is 764 K. 相似文献
15.
Measurements have been made of the transit times of pulses of longitudinal and transverse ultrasonic waves propagating in single crystal LaB6 at room temperature. A unique set of values for the three independent elastic constants has been calculated from the resultant velocities and is; C11 = (45.33 ± 0.11) × 1011dynecm-2, and C44 = (9.01 ± 0.05) × 1011dyne/cm2. The Debye temperature of LaB6 from these measurements is 773 K, which agrees relatively well with the X-ray Debye temperature, however, differs much from the calorimetric and electrical resistance Debye temperatures. 相似文献
16.
The effects of a magnetic field on the heat conductivity of the paramagnetic O2 and O2-Ar gas mixtures of different compositions have been studied by using the hot-wire method. The magnetic field has been applied perpendicular to the temperature gradient so that the fractional change () of the longitudinal coefficient of thermal conductivity has been measured. For pure O2, after applying proper corrections the experimental data obtained by using the hot-wire method agreed well with those obtained by using other methods. The experimental () data have been interpreted by applying the theory of Knaap and Beenakker and treating O2 as a mixture of ms = 0 and ms = ± 1 states.For O2-Ar mixtures, the theory of Köhler and Raum has been used and O2 has been treated as a mixture of ms = 0 and ms = ±1 states. By using this approximation, the experimental () data have been interpreted fairly well and reasonable values of several cross sections have been obtained. 相似文献
17.
18.
H.H. Eggenhuisen L.P. Ekström G.A.P. Engelbertink H.J.M. Aarts J.A.J. Hermans 《Nuclear Physics A》1977,285(1):167-188
Yrast levels in 40K and 40Ar have been investigated with the 26Mg(16O, pnγ)40K and 26Mg(16O, 2pγ)40Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The 40K decay scheme involves new high-spin levels at Etx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of to the 40K levels at Ex = 0.89, 2.88, 4.37, 4.88 and 6.23 and of levels at Ex = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported. 相似文献
19.
Using new experimental information on low-energy πN elastic scattering we recalculate both the low-energy partial waves and the expansion coefficients of about the point ν = 0, t = 0. We use the values to recalculate the πN σ term obtaining 66 ± 9 MeV. We comment on some other recent determinations of this quantity. 相似文献
20.
The high-spin level structures of 152Dy and 153Dy were studied experimentally with 154, 155Gd(α xnγ) in-beam reactions, and for 152Dy also with reactions. The experiments included measurements of singles γ-ray and conversion-electron spectra, γ-ray angular distributions and Eγ-t and Eγ-Eγ-t coincidences. A multiplicity filter set-up was used to study the feeding and decay of isomeric states in 152Dy. In 152Dy about twenty so far unknown levels were found, including two high-spin isomeric states with at excitation energies Ex ≈ 5.04 and 6.08 MeV, respectively. These states are compared with recent calculations on yrast traps. The level scheme of 153Dy contains 28 levels up to Ex = 4.1 MeV and . Band structures in both nuclei are discussed in comparison with other N = 86 and N = 87 isotones. 相似文献