Comment on On the Theory of Nuclear Resonant Forward Scattering of Synchrotron Radiation

Recently, in a paper by Kohn and Smirnov, a formula previously derived by Kagan et al. was developed to explain the forward scattering of gamma radiation by a nuclear-resonant sample excited by pulsed synchrotron radiation. Their derivation followed, directly, a procedure developed by Heitler, Harris, and Hoy. Previously, a completely different formula was developed by Hoy et al. to explain the same process. As a result, Kohn and Smirnov discuss the correctness and validity of the two models. In this Comment a detailed numerical comparison of the two theories has also been made. It is shown that their comparison is substantially inaccurate. The two models give essentially the same results. There is some small difference at times long after the synchrotron radiation pulse. If experiments of this type are used to extract nuclear parameters, either model will provide the same results. Either model will fit the experimental data well

Instantaneous processing of "slow light": amplitude-duration control, storage, and splitting

Nonadiabatic change of the control field or of the low-frequency coherence allows for an almost instantaneous change of the signal field propagating in a thick resonant absorber where electromagnetically induced transparency is realized. This finding is applied for the storage and retrieval of the signal, for the creation of a signal copy and separation of this copy from the original pulse without its destruction.Comment: 9 pages, 1 figure, submitted to PRL on 18, December, 200

Gamma Echo Interpreted as a Phase-Shift Induced Transparency

In the gamma-echo technique a radioactive source is moved, with respect to a nuclear-resonant absorber, during the lifetime of first-excited nuclear state. This introduces a phase shift between the source radiation and the radiation from the absorber. If the source is moved abruptly, introducing a pi phase shift, the time-dependent intensity shows a sharp increase in the intensity at that time, the gamma echo. Using the recently developed one-dimensional quantum-mechanical model, based on the technique developed by Heitler and Harris, the gamma-echo effect is seen to be a phase-shift-induced transparency. A closed-form solution for the time-dependent transmitted intensity has been obtained. The solution has the form of a sum over coherent paths that the radiation takes in going from the radioactive source through the absorber to the detector. The model shows that the sharp increase in the intensity, the gamma echo, at the time when the source is moved abruptly is due to constructive interference, starting at that time, between the source radiation and the radiation from the absorber. The exact. form of the gamma-echo spectrum depends on the movement of the source. Shapes having multiple peaks are possible. All shapes can be found using the one-dimensional model

Coherent-Path Model for Nuclear Resonant Scattering of Gamma Radiation From Nuclei Excited by Synchrotron Radiation

Previous theoretical descriptions of nuclear resonant scattering of synchrotron radiation have been based on the semiclassical optical model or on several quantum mechanical models. These models are fine but do not give a clear physical picture of all the processes. The theory presented here gives a clear physical picture of all the relevant aspects of nuclear resonant scattering. The model treats the nuclear resonant sample as a one-dimensional chain of effective nuclei. However, the model is deceptive. It only appears to be one dimensional. It actually treats the sample as a series of effective planes. The analysis uses the time-dependent quantum mechanical techniques due to Heitler. A closed form solution, for the time-dependent forward scattered intensity, is found. The only parameter in the theory is N the number of effective nuclei (planes) in the model. It is shown that the prominent experimental features, the speed-up and dynamical beat effects, are primarily due to a π phase change of reemitted radiation. compared to the incident radiation, that occurs when radiation is absorbed and reemitted without recoil by a single \u27\u27effective nucleus (plane). The model also predicts results for the incoherent processes

Adiabatic following criterion, estimation of the nonadiabatic excitation fraction and quantum jumps

An accurate theory describing adiabatic following of the dark, nonabsorbing state in the three-level system is developed. An analytical solution for the wave function of the particle experiencing Raman excitation is found as an expansion in terms of the time varying nonadiabatic perturbation parameter. The solution can be presented as a sum of adiabatic and nonadiabatic parts. Both are estimated quantitatively. It is shown that the limiting value to which the amplitude of the nonadiabatic part tends is equal to the Fourier component of the nonadiabatic perturbation parameter taken at the Rabi frequency of the Raman excitation. The time scale of the variation of both parts is found. While the adiabatic part of the solution varies slowly and follows the change of the nonadiabatic perturbation parameter, the nonadiabatic part appears almost instantly, revealing a jumpwise transition between the dark and bright states. This jump happens when the nonadiabatic perturbation parameter takes its maximum value.Comment: 33 pages, 8 figures, submitted to PRA on 28 Oct. 200

生命周期、人力资本与家庭房产投资消费的关系——来自全国调查数据的经验证据

本文对生命周期和人力资本与家庭房产消费投资之间关系进行探索分析。对生命周期中的出生年代和年龄效应进行了区分,在出生年代效应方面,出生越早的人对投资房产的兴趣越高;年龄效应则使家庭房产的消费投资在人生命周期的一定阶段达到最大,随后降低,呈现驼峰形曲线。人力资本越高的家庭,对房产消费投资的可能性越低。生命周期与人力资本对家庭房产消费投资存在显著的交互影响,在相同出生年代(或相同年龄)的情况下,人力资本高(教育程度高)的家庭相对人力资本低(教育程度低)的家庭更不倾向于对房产进行消费投资

Pulse transformation and time-frequency filtering with electromagnetically induced transparency

A simple analytical solution for the propagation of a weak Gaussian pulse in a dense absorptive medium with electromagnetically induced transparency is found. This solution is applied to the analysis of three regimes: (1) and (2) the pulse spectrum is narrower than the transparency window [which is narrow (1) or wide (2) with respect to the width of the absorption line] and (3) the pulse spectrum is broader than the transparency window. It is shown that the pulse maintains its area in all three regimes and maintains its Gaussian shape but narrows in spectrum in regime 1. In regime 2, the pulse begins to distort after a certain distance. In regime 3, the pulse is split into two parts. One part is an adiabatic part with a spectrum defined by the effective width of the transparency window for a thick medium and the other is an oscillating nonadiabatic part of short duration. The adiabatic part propagates slowly and the nonadiabatic part propagates with a velocity close to the speed of light. Thus in regime 3, the medium acts as a time-frequency filter, separating the narrow and wide spectrum components of the pulse in time at the output of the absorber. ©2005 The American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe