共查询到20条相似文献,搜索用时 31 毫秒
1.
G.A. Kluitenberg 《Physica A》1977,87(2):302-330
It has been shown by the author in a previous paper that thermodynamic vectorial internal degrees of freedom which influence the polarization or the magnetization of a medium may give rise to dielectric or magnetic relaxation phenomena. Snoek's equation for magnetic relaxation phenomena was derived and it was shown that Debye's theory for dielectric after-effects in polar liquids is a special case of the developed theory. In this paper it is shown that if Z is some vectorial internal degree of freedom which influences the polarization a new internal degree of freedom bip(int) may be defined which is a function of biZ, which may replace biZ as vectorial internal degree of freedom and which is a part of the total specific polarization. Furthermore, p(int) may be introduced in such a way that the remaining part of the polarization, p(el) (defined by , where p is the total polarization per unit of mass), has the property that it vanishes for all values of p(int) if the medium is in a state where the electric field E and the mechanical elastic stresses vanish and the temperature of the medium equals some reference temperature. If the equations of state are linearized the latter result implies for an isotropic medium , where ρ is the mass density and a(0,0)(P) a constant. On the other hand p(int) satifies a relaxation equation. It is seen that the use of p(int) as an internal degree of freedom is of great advantage. This is connected with the fact that p(int) is a measurable quantity in contradistinction to an arbitrary “hidden” vectorial internal degree of freedom. Analogous results may be obtained for magnetic after-effects. 相似文献
2.
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
3.
Results from a CCBA analysis of the 28Si(d, 3He)27Al reaction are reported. The transfers are assumed to occur between dominant components of (λμ) symmetry (0, 12) and (2, 10) in the initial and final nuclear eigenstates respectively. The results show that cross sections to four of the six levels observed below 3 MeV can be fairly well reproduced within a pure K(J) band framework. However, consistent with electromagnetic results, all six levels can be fit if the K(J) band purity of the analysis, SU(3) model. states and state is abandoned. 相似文献
4.
Mössbauer spectra were obtained of the paramagnetic spinels and susceptibilities were measured. The strong difference between the paramagnetic Fe2+ and Fe3+ spectrum, due to the different quadrupole splitting, is used for the distinction between the two species. At 300 K a superposition of the Fe3+ and the Fe2+ spectra is found for most of the iron and, in addition, some continuous absorption. The latter is strongest for equal Fe3+ and Fe2+ concentration while it disappears towards the end members (Fe3+ only or Fe2+ only) as well as with decreasing temperature (between 78 and 200 K). From this it is concluded that it arises from thermally activated electron exchange, the frequency of which passes a “critical” value of ~108 sec?1 for increasing temperature. Paramagnetic susceptibilities are found to obey a Curie-Weiss law down to low temperatures. From the dependence of the asymptotic Curie temperature on the composition the magnetic interaction parameters J11 = ?1.4 K, J22 = ?3.3 K and J12 = + 1.6 K for the Fe3+Fe3+, Fe2+Fe2+ and Fe3+Fe2+ interactions are derived. The experimental results are discussed in terms of a hopping model with an activation energy q ~- 0.12eV and a non-equivalence of the octahedral sites expressed by a varying potential energy difference U0 between neighbouring sites. The continuous absorption at 300 K for is attributed to about 17% of the iron on sites with U0 running from 0 to ??0.06 eV. The ferromagnetic Fe3+, Fe2+ interaction (J12) is attributed to electron transfer from localized Fe2+ ions to Fe3+ neighbours via a transfer integral b of the order of 0.05 eV. The magnitudes of J12 and b are tentatively explained. 相似文献
5.
6.
G.C. Salzman Gerald G. Ohlsen J.C. Martin J.J. Jarmer T.R. Donoghue 《Nuclear Physics A》1974,222(3):512-524
Angular distributions of six polarization transfer coefficients ; of the four analyzing powers Ay(θ), Axx(θ), Ayy(θ), and Azz(θ); and of the polarization function Pý(θ), have been measured atEd = 10.00 MeV for the reaction 2H(d, n)3He. Measurements were made for neutron lab angles between 0° and 80° in 10° steps. Additionally the y-axis associated quantities were measured at θ1ab = 99°. Most of the measured coefficients are large at some angles and all show considerable variation with angle. 相似文献
7.
W. Steffen H.-D. Gräf W. Gross D. Meuer A. Richter E. Spamer O. Titze W. Knüpfer 《Physics letters. [Part B]》1980,95(1):23-26
The search for magnetic dipole transitions from the ground state-even Ca isotopes to high lying Jπ=1+ states by means of low momentum transfer but high resolution inelastic electron scattering is described. The previously detected strongly excited Jπ=1+ state EX=10.319 MeV [B(M1)↑=1.12±0.27μK2] in 40Ca has been confirmed, but - contrary to the expectations of the independent particle shell model - only a fairly weak M1 transition is observed in and none in 44Ca between EX=8.2?12.2 MeV. In 48Ca, however, a very strong M1 transition [B(M1) ↑ = 4.0 ± 0.3 μ2K] to a single state at EX=10.227 MeV has been discovered. 相似文献
8.
Ryohei Nakata Katsuyasu Kawano Minoru Sumita Elichi Hlguchi 《Journal of Physics and Chemistry of Solids》1980,41(10):1119-1126
The characteristics of allowed and forbidden transitions of Eu2+ ions in CaF2 single crystals have been investigated at room temperature. The Angular dependences of these transition intensities were theoretically calculated with the use of perturbation theory, and compared with the experimental values. The experimental results can be explained by taking into account crystal field effects , and a hyper fine interaction AiS · Ii in the spin Hamiltonian. 相似文献
9.
About ScienceDirect 《Nuclear Physics A》1983,410(3):531-533
High-spin states in 167,168Hf and 170, 171W have been excited by the reactions . The yrast bands have been observed up to in 167Hf, Jπ = 28+ in 168Hf, in 171W and Jπ = 22+ in 170W. Both even-even nuclei display a strong backbend around Jπ = 14+, whereas 167Hf shows an upbend at ω ~- 0.33 MeV and 171W exhibits a progressive gain in aligned angular momentum above ω ~- 0.26 MeV. At even higher rotational frequencies, bridges have been found in the central valleys of the γ-γ correlation matrices at ω ~- 0.42 and 0.52 MeV for the Hf isotopes and ω ~- 0.45 and 0.47 MeV for the W isotopes. Deduced moments of inertia for the Hf isotopes using the correlation data show a smooth increase up to about the rigid-sphere value at ω ~- 0.5 MeV. The data are satisfactorily accounted for by cranked shell-model calculations. In particular, a qualitative interpretation is given for the experimentally observed systematic difference in the strength of the interaction potential for the N = 95 and N = 97 isotopes of Hf and W. 相似文献
10.
A frequency tunable infrared source has been constructed by using the (Ar-laser) - (dyelaser) difference frequency method developed by Pine and applied to the observation of the overtone bands of PH3 3ν2 ← 0 and 4ν2 ← ν2 in the 3.4 μm region and 4ν2 ← 0 in the 1.6-μm region. A Stark modulation method was used to increase the sensitivity of detection. For transitions which were well modulated, the minimum detectable absorption coefficient was estimated to be ~3 × 10?7 cm?1 using a 3-m cell. Emphasis was placed on the observation of the A1-A2 splitting for K = 3n rotational levels. For the 3ν2 state splittings were observed for K = 3, 6, and 9 because PH3 is a very nearly spherical top in this state. The magnitude and the J dependence of the observed K = 3n splittings have been analyzed by using a normal symmetric rotor Hamiltonian and a centrifugal distortion term of the form . 相似文献
11.
R.F. Curl 《Journal of Molecular Spectroscopy》1973,48(1):165-173
The and transitions of the J = 7 levels of the ground state of CH4 have been observed by infrared-radio frequency double resonance using the 3.39 μ HeNe laser line. The transition frequencies are 423.02 ± 0.02 MHz and 1246.55 ± 0.02 MHz, respectively. Using these frequencies and the splitting of the E and F2 levels of the J = 2 state calculated from the molecular beam magnetic resonance spectra of Ozier, the centrifugal distortion constants are derived to be Dt = 132933 ± 10 Hz, H4t = ? 16.65 ± 0.2 Hz, and H6t = 10 ± 1 Hz. The J = 15 E(1) → E(2) microwave transition is predicted as 14150 ± 9 MHz. 相似文献
12.
The resonant 2-photon E(O+g) ← B(O+g) ← X(O+g) transition of I2 vapor has been studied by polarization spectroscopy, leading to a rotational analysis of the ν = 0–15 vibrational levels of the E state. The principal constants determined are . 相似文献
13.
Resonances in the reaction 56Fe(p, γ)57Co have been surveyed over the energy range 1.2 ? Ep ? 1.5 MeV wherein the analogues of the ground state state and 0.136 MeV state of 57Fe are expected to occur. Gamma-ray angular distributions have been used to establish resonance and bound-state spins, and decay schemes have been determined. The analogue resonances appear to be severely fragmented, however the density of resonances of a given spin correlates quite well with (3He, d) results and with the expected analogue-state positions. 相似文献
14.
D.M. Edwards 《Journal of magnetism and magnetic materials》1984,45(1):151-156
It is shown how disordered local-moment states, in a metal such as Fe, may be stabilized by constraining magnetic fields. Effective interaction parameters between moments are defined in terms of spin density functional theory. On removing the constraints the moments initially precess but then decay rapidly, the latter process leading to an energy width of S(q, ω) at large q of order , where TC is the Curie temperature and W is the width of the d-band. T he consequences for neutron scattering experiments are discussed and the rather different case of Ni is considered. 相似文献
15.
Jon T. Hougen 《Journal of Molecular Spectroscopy》1984,106(1):134-154
Rotational energy levels in vibronic ground states of 2A, 2E, and 2F electronic states of open-shell XY4 molecules, as well as rotational line intensities for allowed transitions between such states, are discussed, including the effects of spin-orbit interaction and tetrahedral splittings. Jahn-Teller effects are assumed to be small, and are only taken into account implicitly, through their contributions to various parameters in the effective Hamiltonian. Qualitative information is obtained by considering several limiting-case coupling schemes among the electron spin angular momentum S, the electron orbital angular momentum L, and the pure rotational angular momentum R. These limiting cases are similar in spirit to Hund's coupling cases in diatomic molecules, but differ sufficiently from the latter to make detailed correspondences unhelpful. Quantitative information on rotational energy levels and line intensities is obtained numerically by diagonalizing a Hamiltonian matrix set up in a basis set characterized by uncoupled moleculefixed projections of S, L, and the total angular momentum J, and symmetrized so that all basis set functions belong to a definite species in the subgroup D2d of the true point group Td. Hamiltonian matrix elements are determined by ladder operator techniques. Three sample calculated spectra, corresponding to , , and are presented. As one might expect, when the spin-orbit constant A is set equal to zero, then both qualitative and quantitative aspects of the rotational-electronic problem in open-shell XY4 molecules can be mapped easily onto discussions of the rotation-vibration problem from the CH4 literature. 相似文献
16.
The analysing power of the 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 and 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
17.
The hyperfine splitting frequencies gμNBH.F./h of 2.7 h 93Tc , 4.9 h 94Tc (Jπ = 7+) and 20 h 95Tc as dilute impurities in Fe have been measured with NMR on oriented nuclei as 336.36(5) MHz, 175.11(1) MHz and 315.97(2) MHz, respectively. From the resonance shifts with an external magnetic field B0 the hyperfine field of Tc has been determined as -317(5) kG. Taking this into account the nuclear g-factors are deduced as . 相似文献
18.
Yu.B. Bushnin A.F. Dunaitsev R.I. Dzelyadin S.V. Golovkin V.F. Konstantinov V.P. Kubarovsky L.G. Landsberg V.M. Leontiev G.P. Makarov V.A. Mukhin V.G. Rybakov T.I. Petrunina Yu.N. Simonov V.V. Smirnov A.M. Zaitsev A. Zallo 《Physics letters. [Part B]》1976,64(1):102-106
The difference of the cross sections for deep inelastic scattering of muons with average momenta 21 GeV/c with right and left helicity at large angles, i.e., with large momentum transfer, has been measured. No statistically-significant dependence of cross sections on the longitudinal polarization of muons has been found, i.e. no parity-nonconservation effects in deep inelastic μN interaction have been observed. The magnitude of the cross-section asymmetry may be represented as R = β〈Q2〉 = (? 4 ± 6) × 10?3 〈Q2, (GeV/c)2〉. The limitations Go(μ) = (+ 6 ± 10)G have been obtained for the constant Go(μ) of vector-axial interaction (hadron, V-A). 相似文献
19.
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
20.
Jon T Hougen 《Journal of Molecular Spectroscopy》1973,46(3):490-501
To a good approximation, hyperfine splittings for F1 and F2 rotational levels of the ground vibrational state of 12CH4 depend linearly on three hyperfine interaction parameters. Coefficients in these linear expressions have been computed in a relatively simple manner and tabulated for levels with 1 ≤ J ≤ 20. The hyperfine pattern for the level computed from these expressions using values for the three hyperfine interaction parameters reported recently by Yi, Ozier and Ramsey (1) agrees well with the pattern obtained from new HeNe laser measurements of Hall and Bordé (2) on the line of the ν3 band of methane. 相似文献