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1.
W. Bauer K. Maier J. Major H. -E. Schaefer A. Seeger H. -D. Carstanjen W. Decker J. Diehl H. Stoll 《Applied Physics A: Materials Science & Processing》1987,43(4):261-267
A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a fast positron lifetime spectrometer based on
+
coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventional lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.This paper is based on a talk given by W.B. at the Int. Symp. Production of Low-Energy Positrons with Accelerators and Applications, held at Justus-Liebig-Universität Giessen, FRG, September 25–27, 1986 相似文献
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V. N. Fetisov L. Majling J. Žofka R. A. Eramzhyan 《Czechoslovak Journal of Physics》1986,36(3):451-454
The applicability of (K
–,–) - and (K
–,–
N)-reactions on13,14C and14,15N nuclei to the study of -transitions in primary and daughter -hypernuclei is discussed. The intensity of -deexcitation of
13C state |S
12C(15·11 MeV; 1+1): 1/2+ has been shown to be comparable with the intensity of baryon decay. Isospin selection rules are used to distinguish excitation energy ranges of primary hypernuclei, where the identification of the secondary -lines is probable.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985. 相似文献
5.
, , . , . .
The damping of particle oscillations in a general field with periodic structure I
A liner theory is derived, discussing the dynamics of particles in the region of an equilibrium orbit in a general electromagnetic field, which forms a periodic system. The total particle damping is determined from the Hamiltonian found and from dissipative forces brought out by a classical reaction radiation. Relations for the damping of the synchrotron oscillations are derived from the study of the appropriate phase space.相似文献
6.
T. A. Aibergenov P. S. Baranov O. D. Beznisko S. N. Cherepnija L. V. Fil'kov A. A. Nafikov A. I. Osadchiy V. G. Raevskiy L. N. Shtarkov E. I. Tamm 《Czechoslovak Journal of Physics》1986,36(8):948-951
The cross section for the radiative photoproduction of
+ mesons on hydrogenp
+
n in dependence on the momentum transfer squared has been measured at the 1·2 GeV electron synchrotron PACHRA. Using extrapolation of the data to pion pole the differential cross section for the pion Compton scattering
+
+ has been obtained, and the electric polarizability of the
+ meson has been estimated to be
=(20±12) x 10-43cm3.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.The authors thank P. A. Cherenkov for his constant attention to this work and helpful discussions at all stages of the work. 相似文献
7.
For a one-dimensional configurational glass model we have performed molecular dynamical calculations. The Newtonian equation of motion was solved numerically including a damping term. The residual energye
res() as a function of the damping constant , exhibits a power law behavioure
res(),0.061; in an intermediate range of . This behaviour can be explained as the freezing of a certain type of two level systems with an excitation energy and a barrier heightB. The exponent is approximately equal to /B. This relationship is justified analytically.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
8.
The low-lying levels in 127La have been studied through the -decay of 127Ce ( T1/2 = 29s) produced by bombarding a natMo target with a 185-MeV 35Cl beam. Reaction products were on-line mass-separated, and -ray singles and - coincidence measurements were performed. Conversion electrons were also measured and multipolarities of transitions have been derived. The half-life of the 210.9-keV level was determined to be (1.9±0.3)ns by the - delayed coincidence technique. The level scheme obtained has been compared with calculations based on the Nilsson model. 相似文献
9.
Václav Bartošek 《Czechoslovak Journal of Physics》1956,6(5):505-512
d
-
l
-
t
d
R
max
-
J
, ( )
-
-
, . .
-
( )
-
-
R
R
max —R.
, 相似文献
10.
Inelastic electron scattering at a neon atom in the presence of an external electric field is considered. The distortion factors of the cross section
M
(F) are calculated for a series of 4d and 5d levels. It is shown that the distortion factor in strong fields is a nonlinear and nonmonotonic function of the field. The distortion factors and transition probabilitiesA
, are compared. The correlation between the behavior ofA
, and
M
(F) is explained by the dependence of the mean dipole moment of the Stark state on the field strength.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 97–110, January, 1996. 相似文献
11.
In the Gd monochalcogenides up to three different structural distortions have been detected in the magnetically ordered regime. Our experiments indicate that all three phases show type II antiferromagnetic order but with different orientations of the magnetic moments: A truly trigonal phase withm
k
k=[1/2, 1/2, 1/2], a monoclinic phase withabc, =/2+, and the spins oriented along [110], and a pseudo-rhombohedrally compressed monoclinic phase with the spins in the (111) planes. The spin flips can be accounted for by a model including anisotropic exchange interactions. 相似文献
12.
Alan D. Sokal 《Journal of statistical physics》1981,25(1):25-50
A variety of rigorous inequalities for critical exponents is proved. Most notable is the low-temperature Josephson inequalitydv +2 2–. Others are 1 1 +v, 1 1
, 1,d 1 + 1/ (for d),dv, 3 + (for d), 4 , and 2m 2m+2 (form 2). The hypotheses vary; all inequalities are true for the spin-1/2 Ising model with nearest-neighbor ferromagnetic pair interactions.NSF Predoctoral Fellow (1976–1979). Research supported in part by NSF Grant PHY 78-23952. 相似文献
13.
This article presents a Pauli-Dirac matrix approach to Clifford Algebras. It is shown that the algebra C2 is generated by two Pauli matrices i2 and i3; C3 is generated by the three Pauli matrices 1, 2, 3; C4 is generated by four Dirac matrices 0, 1, 2, 3 and C5 is generated by five Dirac matrices i0, i1, i2, i3, i5. The higher dimensional anticommuting matrices which generate arbitrarily high order Clifford algebras are given in closed form. The results obtained with this Clifford algebra approach are compared with the vector product method which was described in a recent article [Found. Phys.
10, 531–553 (1980) by Poole, Farach and Aharonov] and with the Dirac, Rashevskii and Ramakrishnan methods of matrix generation.Supported by the National Science Foundation under Grant ISP-80-11451. 相似文献
14.
K. Svozil 《Foundations of Physics》1995,25(11):1541-1560
Inasmuch as physical theories are formalizable, set theory provides a framework for theoretical physics. Four speculations about the relevance of set theoretical modeling for physics are presented: the role of transcendental set theory (i) in chaos theory, (ii) for paradoxical decompositions of solid three-dimensional objects, (iii) in the theory of effective computability (Church-Turing thesis) related to the possible solution of supertasks, and (iv) for weak solutions. Several approaches to set theory and their advantages and disadvatages for physical applications are discussed: Canlorian naive (i.e., nonaxiomatic) set theory, contructivism, and operationalism. In the author's opinion, an attitude of suspended attention (a term borrowed from psychoanalysis) seems most promising for progress. Physical and set theoretical entities must be operationalized wherever possible. At the same time, physicists should be open to bizarre or mindboggling new formalisms, which need not be operationalizable or testable at the lime of their creation, but which may successfully lead to novel fields of phenomenology and technology. 相似文献
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H. Albrecht H. Meierling E. F. Wassermann H. Zähres F. T. Hedgcock 《Zeitschrift für Physik B Condensed Matter》1982,49(3):213-220
The impurity contribution to the resistivity in zero field (T) of dilute hexagonal single crystals of ZnMn, CdMn and MgMn has been studied in the mK range on samples cut parallel () and perpendicular () to thec-axis, using a SQUID technique for the measurements. Typical spin glass behavior is found in (T) as well as (T) for all alloys, with Kondo like logarithmic increases at higher temperatures and maxima atT
m at lower temperatures, indicating the influence of impurity interactions. The differences in the corresponding isotropic resistivity poly(T) between the three systems can qualitatively be understood within the framework of a theoretical model by Larsen, describing (T) as a function of universal quantitiesT/T
K and RKKY/T
K
, where RKKY is the RKKY-interaction strength andT
K the Kondo temperature. With respect to the two lattice directions studied, the behavior of (T and (T is anisotropic in the Kondo regime as well as in the range where ordering becomes important. While the anisotropy in the Kondo slope can be understood by an anisotropic unitarity limit, the understanding of the anisotropy in region where impurity interactions are important remains problematic.Dedicated to Prof. Dr. S. Methfessel on the occasion of his 60th birthday 相似文献
17.
We present and discuss the derivation of a nonlinear nonlocal integrodifferential equation for the macroscopic time evolution of the conserved order parameter (r, t) of a binary alloy undergoing phase segregation. Our model is ad-dimensional lattice gas evolving via Kawasaki exchange with respect to the Gibbs measure for a Hamiltonian which includes both short-range (local) and long-range (nonlocal) interactions. The nonlocal part is given by a pair potential dJ(|x–y|), >0 x and y in d, in the limit 0. The macroscopic evolution is observed on the spatial scale –1 and time scale –2, i.e., the density (r, t) is the empirical average of the occupation numbers over a small macroscopic volume element centered atr=x. A rigorous derivation is presented in the case in which there is no local interaction. In a subsequent paper (Part II) we discuss the phase segregation phenomena in the model. In particular we argue that the phase boundary evolutions, arising as sharp interface limits of the family of equations derived in this paper, are the same as the ones obtained from the corresponding limits for the Cahn-Hilliard equation. 相似文献
18.
The electric quadrupole moment of the 9/2– isomer in the171Ta nucleus, populated in the159Tb(16O,4n)171 Ta reaction, has been measured for the first time using the TDPAD technique. The measured value Q(9/2–)=3.09(19) b andB(M1)/B(E2) ratios, deduced from the existing -ray spectroscopic data, have been used to derive shape parameters for the h11/2 band based on this isomer. The present results are consistent with a quadrupole deformation=0.22(1),=00±100. 相似文献
19.
. Ra+Be . , , . 8. 相似文献
20.
F. V. Adamian G. G. Akopian H. H. Vartapetian P. I. Galumian V. H. Grabsky V. V. Karapetian G. V. Karapetian V. K. Oktanian 《Czechoslovak Journal of Physics》1986,36(8):945-947
The beam asymmetryB has been measured for the reactiond pn in the energy rangeE
= 0·4 ÷ 0·8 GeV and angles
p
cm
= 45 ÷ 95° and ford 0d at energiesE
=0·5, 0·6, 0·7 GeV and angle
cm
= 130°. The results obtained are compared to existing theoretical predictions which take into account the possible contribution of dibaryon resonances.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985. 相似文献