共查询到20条相似文献,搜索用时 31 毫秒
1.
R.M. Macfarlane 《Solid State Communications》1974,15(3):535-538
We have observed inter-term Raman scattering from 5T2g→5Eg Frenkel excitons in antiferromagnetic FeF2. It differs qualitatively from previously observed intra-term scattering in a sharply reduced zero-phonon cross section and the appearance of relatively strong exciton-phonon scattering. Since the Raman process is fully allowed, it is possible to measure excited state Debye-Waller factors, D, and we find and . 相似文献
2.
H. Venghaus 《Journal of luminescence》1978,16(3):331-341
Luminescence measurements were performed on high purity epitaxial n-GaAs for various excitation intensities I0 in the range . The luminescence line corresponding to the radiative decay of the shallow donor bound exciton, (D0, X), broadens with increasing I0 and appears as a doublet for , while the two-electron replica of the (D0, X) remains a single narrow line. The doublet structure of the (D0, X) at elevated excitation levels is due to missing luminescence intensity in the center of the line as a consequence of low (D0, X) concentration in a layer extending 1–2 μm from the sample surface into the bulk. The low concentration of (D0, X) is attributed to capture of (D0, X) quanta into surface states, extending to lower energies from the Fermi level fixed by the shallow donors. Comparison of the present results with luminescence spectra obtained by various authors reveals, that unexplained spectral features in the (D0, X) region of n-GaAs reported in the literature are a consequence of high excitation intensity and correspond to the effect reported here. In partly compensated p-GaAs with donor concentrations as given above, the (D0, X) did not transform into a doublet structure even at excitation intensity. 相似文献
3.
H. Albrecht U. Binder G. Harder A. Philipp W. Schmidt-Parzefall H. Schröder H.D. Schulz R. Wurth A. Drescher B. Gräwe U. Matthiesen H. Scheck J. Spengler D. Wegener K.R. Schubert J. Stiewe R. Waldi H. Gennow 《Physics letters. [Part B]》1985,158(6):525-530
Using the ARGUS detector at DORIS II, we have observed a signal of 36.7±8.0 events in the decay channel D0→Ks0φ. In the same data sample, we have observed the well established decay D0→Ks0π+π?, and find the ratio, , to be 0.186±0.052. The substantial value of (0.99±0.32±0.17)% then derived for the branching ratio for gives direct evidence that W exchange contributes D0 decay. 相似文献
4.
A. Honders J.M. der Kinderen A.H. van Heeren J.H.W. de Wit G.H.J. Broers 《Solid State Ionics》1985,15(4):265-276
Two electrochemical methods - involving the application of a long-time galvanostatic current pulse and a small potentiostatic voltage step to a M/MxSSE cell - are presented. From the overvoltage, respectively current response the chemical diffusion coefficient () and the thermodynamic factor (? ln a/? ln c) are obtained. The methods have been applied to the cells: Li/1M·LiClO4 in propylenecarbonate/LixTi1.03S2 0.05 < x < 0.95, T = 20°C; and LixCoO2 0.10 < × < 1, T = 20°C. From the application of the current pulse/voltage decay method it followed: , with a slight tendency to increase with decreasing x; , decreasing with decreasing x. These values are among the highest found for solid state Li+-ion diffusion, and will be closely evaluated and compared with data reported by other workers. The x-dependence of the thermodynamic factor, determined from kinetic data, for LixTi1.03S2 (x = 0.05-0.95) and LixCoO2 (x = 0.60-1.00) is in accordance with a simple thermodynamic model. Unlike for LixTi1.03S2, the thermodynamic factor for LixCoO2, determined from the EMF-x relation, cannot be accounted for by this model. Furthermore, a fast, but crude method to determine the average chemical diffusion coefficient in LixTi1.03S2 and LixCoO2 is discussed. 相似文献
5.
6.
J. Heintze G. Heinzelmann P. Igo-Kemenes R. Mundhenke H. Rieseberg B. Schürlein H.W. Siebert V. Soergel H. Stelzer K.-P. Streit A.H. Walenta 《Nuclear Physics B》1979,149(3):365-380
The decay K+ → e+υγ has been investigated. For the structure-dependent part with positive γ-helicity (SD+) the branching ratio is obtained from 51 ± 3 events observed in the kinematical region Ee ? 235 MeV, Eγ > 48 MeV and θeγ > 140°. For the corresponding part with negative γ-helicity we obtain an upper limit Γ(SD?)/Γ(SD+) < 11 (90% CL) from the sample of electrons with energies 220 MeV ? Ee < 230 MeV and with no γ in the backward direction. This upper limit implies that the ratio of structure-dependent axial vector amplitudes lies outside the region .For the decay the limit 90% confidence level) was found. 相似文献
7.
Jan Finjord 《Physics letters. [Part B]》1982,109(3):227-230
We unify the color-octet weak transitions first studied in cq? annihilation models with the coherence structure of c-quark decay models. We find then, with a dominant c-quark decay contribution, and τ(D+)≈7.5×10?13 s, not inconsistent with the trends in the experimental results. 相似文献
8.
H. Taureg G. Zech F. Dydak F.L. Navarria P. Steffen J. Steinberger H. Wahl E.G.H. Williams C. Geweniger K. Kleinknecht 《Physics letters. [Part B]》1976,65(1):92-96
The branching ratio has been determined to be (2.68±0.15)×10?3 for photon energies greater than 50 MeV in the KS0 rest frame. The decay KS0→π+π?γ is found to be dominated by the internal bremsstrahlung transition. The branching rato of a possible direct transition is found to be less than 0.06 × 10?3 at 90% confidence level for . 相似文献
9.
An investigation of the γ-decay of the 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 (, ) and (). The spin of the Ep = 3547 keV resonan is, from angular distributions, uniquely determined to be and this state is found to be the unfragmented analogue state of the , 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
10.
11.
Three-, two-, and one-dimensional disordered systems with randomly distributed, purely repulsive scattering centers, known as Lorentz models, are studied in the low energy limit [1]. Using a functional integral representation and a version of the “replica trick”, we have found in the D-dimensional system the density of electronic levels of the form and the constants b0, b1,…, bD, and γ have been determined. 相似文献
12.
H. Braun M. Cornelssen H.-U. Martyn O. Erriquez S. Natali F. Romano D. Bertrand M. Csejthey-Barth J. Lemonne P. Renton P. Vilain D.C. Cundy T.I. Pedersen D. Waldren 《Physics letters. [Part B]》1973,47(2):185-188
The q2 variation of the factor in the decay K+→π0e+ν has been studied using a sample of even detected in the CERN 1.1 m3 heavy-liquid bubble chamber. The data are consistent with a linear development with λ+=0.027±0.008. 相似文献
13.
Peter Zimmermann Theodore W. Ducas Michael G. Littman Daniel Kleppner 《Optics Communications》1974,12(2):198-201
We present a new technique for selectively populating excited states which are inaccessible by dipole excitation from the ground state. The method uses a static electric field to introduce a component of a dipole-allowed state into the state of interest. We have applied the method to cesium to measure lifetimes and a Stark mixing coefficient. The results are , , and <62D|;ez |72P>/(E7P?E6D)=0.7(3)×10?3 where is in kV/cm. 141 相似文献
14.
Using a solution to the inverse scattering problem we have generated phase-equivalent separable potentials in the and states, which have nearly the same singlet UPA form factors and deuteron parameters (ED, PD, QD, AS and ) as the Reid soft-core potential. We compare our results for the binding energy of the triton and the neutron-deuteron doublet scattering length with the corresponding values for the Reid soft-core potential. 相似文献
15.
Harry Partridge Charles W. Bauschlicher James R. Stallcop 《Journal of Quantitative Spectroscopy & Radiative Transfer》1985,33(6):653-655
Potential energy curves for the , and states of N+2 that dissociate to N () and , have been determined from a complete active space self-consistent field calculation. The state is found to be significantly bound (De = 2.68 eV) with a minimum at 1.72 Å. 相似文献
16.
Two band groups near 1450 Å, first observed by Tanaka, Yoshino, and Freeman (J. Chem. Phys.62, 4484–4496 (1975)) in discharges through mixtures of helium and argon and assigned by them to the HeAr+ ion, were studied under high resolution. Like the similar spectrum of HeNe+ previously investigated, the spectrum of HeAr+ is a charge transfer spectrum. The upper state B2Σ+ of both band groups is derived from while the two lower states and X2Σ+ are derived from . All three states are very weakly bound, the two lower states even more weakly than the upper state. Unlike HeNe+ most of the HeAr+ bands are violet shaded. In the longward band group each band shows only three branches while in the shortward group there are four. The former observation shows that the state behaves like a 2Σ? state with γv ≈ 0. The B, D, γ, p, and ΔG values of all states were evaluated. While the Bv values of upper and lower states are nearly equal, the Dv values are quite different and this difference accounts for the violet shading of most of the bands even when B′v is slightly smaller than B″v; it also accounts for some of the extraheads and linelike features in the rotational structure. As in HeNe+ the component of 2Π was not observed. 相似文献
17.
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
18.
The cross-relaxation of YAG:Tb3+ has investigated by analysis of the 5D3 decay curve as a function of Tb3+ concentration. This technique is a more sensitive test of the mechanism than relative intensity measurements alone. It is shown that the relaxation is predominantly dipole-dipole in character (R0 ~ 1.3nm), and insensitive to temperature. The population of the 5D4 state following high energy excitation occurs almost entirely via cross-relaxation from the 5D3 state. 相似文献
19.
A. Bolovinos P. Tsekeris J. Philis E. Pantos G. Andritsopoulos 《Journal of Molecular Spectroscopy》1984,103(2):240-256
Absolute extinction coefficient and oscillator strength of pyridine, pyrimidine, pyrazine, and s-triazine were recorded with moderate resolution in the region of 3.5–9.5 eV. Analogous to , 1B1u, transitions of benzene, several and Rydberg transitions are presented and discussed. 相似文献
20.
Two new systems of emission bands near 2100 and 3100 Å have been produced by a microwave discharge in B2S3 vapor. From the known X2Σ+ and A2Πi states of BS, these systems have been assigned as E2Σ+ → X2Σ+ and E2Σ+ → A2Πi. Constants in cm?1 for the new state are , 相似文献