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91.
92.
We consider thermalisation and spontaneous decay of a two-level atom beyond the Markovian approximation. While the standard elimination of the continuum of radiation modes results in exponential decay represented by a Lindblad equation of motion, we use a simple toy model that takes into account the finite relaxation rate of the environment and present an exact non-Markovian master equation of the Nakajima-Zwanzig form. Because the exact derivation of non-Markovian equations has proved very difficult for all more realistic (and hence much more complicated) models, we analyze the master equation obtained and also discuss difficulties that are likely to arise with non-Markovian evolution operators. 相似文献
93.
S.M. Barnett C. Fabre A. Maıtre 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):513-519
We compare two high sensitivity techniques which are used to measure very small displacements of physical objects by optical
techniques: the interferometric devices, measuring longitudinal phase shifts, and the devices used to monitor transverse displacement
of light beams. We detail the differences and the similarities for the quantum limits on the resolution of both systems. In
both cases squeezed light can be used to resolve beyond the standard quantum limit and number correlated states allow us to
reach the “Heisenberg” limit.
Received 12 September 2002 Published online 21 January 2003 相似文献
94.
Y. Y. Lau K. R. Chu L. R. Barnett V. L. Granatstein 《International Journal of Infrared and Millimeter Waves》1981,2(3):373-393
The operation of the gyrotron travelling wave amplifier is based on the convective cyclotron maser instability. It is found that this convective instability may become absolute (nonconvective) at a sufficiently high current level, resulting in oscillation instead of amplification. This threshold current for the transition depends sensitively on the applied magnetic field. The axial wavelength and the characteristic frequency of oscillation at the onset of absolute instability are given. It is found that momentum spread has virtually no effect on the threshold current. A small amount of resistive wall loss, however, raises the threshold current significantly. Oscillations due to partial reflection at the ends of the system are also examined. Preliminary experimental results on both types of oscillations are reported and are found to be in good agreement with the theory. 相似文献
95.
The properties of the negative parity states of55Fe and57Fe are investigated in the framework of the intermediate coupling model. In the model, a neutron or a quasineutron is coupled to anharmonic vibrations of the core. Anharmonicities of the vibrations are estimated through the observed properties of the core. Energy levels, spectroscopic factors and electromagnetic properties have been calculated. The results of the present calculations are also compared with available experimental results and other theoretical results. The model reasonably accounts for many of the properties of the low-lying states. 相似文献
96.
A comprehensive study indicates that equally likely sources for trimuon events neutrino scattering are (a) charged heavy lepton production (with decay to three muons) and (b) simultaneous production of a neutral lepton (with decay to two muons) and a heavy quark (with decay to one muon). The sequential decay of a heavy quark to two muons is less likely. An intriguing model yielding simultaneous M0 and b quark production is proposed. 相似文献
97.
W. Mark Barnett Geng Lin Harvest L. Collier Russell G. Baughman 《Journal of chemical crystallography》1997,27(7):423-427
1,1′-Di(methylacetato)-2,2′-biimidazole, C12H14N4O4, crystallizes from methanol in the space groupP2 1/c, wherea=9.535(2),b=13.385(2),c=5.1208(8) Å,V=652.2(2) Å3, andZ=4.1,1′-Di(chloroethoxyethyl)-2,2′-biimidazole, C14H20Cl2N4O2, crystallizes from cyclohexane in the space groupPbca, wherea=12.372(2),b=8.959(2),c=14.840(2) Å,V=1644.9(5) Å3, andZ=8. The structures were refined toR=0.041 (1380 observed reflections) andR=0.043 (3243 observed reflections), respectively. Both molecules crystallize with coplanar rings and the substituents assume atrans configuration with a center of inversion between the bridging carbon atoms. 相似文献
98.
The signal-to-noise ratio in steliar speckle interferometry is estimated by direct application of photon counting formulae. This treatment demonstrates that the limiting observable magnitudes are dependent on object size. 相似文献
99.
100.
Absorption and fluorescence spectra of Sn2+ and Sb3+ in borax, phosphate, and germanate glasses were measured in the temperature range 87–295°K. Fluorescence decay times of these ions in borax glass at 87°K was a single exponent with τ ≈ 6–11 μsec. At 293°K, two decay times were resolved in the range of 50–2000 nsec. The nonexponential behavior is interpreted by the repopulation of the 3P1 level from the 3P0 level. The temperature dependence of fluorescence and the low values of quantum efficiencies of fluorescence are explained by means of the configurational coordinate diagram model. 相似文献