SYMMETRY PROPERTIES IN THE STUDY OF THE RAYLEIGH-TYPE OPTICAL MIXING SIGNAL IN PRESENCE OF A THERMAL BATH

2013 ◽  
Vol 22 (01) ◽  
pp. 1350007
Author(s):  
J. L. PAZ ◽  
A. MASTRODOMENICO ◽  
M. A. IZQUIERDO
Keyword(s):  
Electromagnetic Field ◽  
Molecular System ◽  
Thermal Bath ◽  
Bloch Equations ◽  
System A ◽  
Symmetry Properties ◽  
Intensity Response ◽  
Optical Mixing ◽  
Cumulant Expansions

In this work are studied the symmetry properties of the Rayleigh-type optical mixing signal of a two-level molecular system immersed in a thermal bath and irradiated by a classical electromagnetic field. The solvent induces a random shift of the Bohr frequency in the molecular system. A methodology based in cumulant expansions is employed to obtain the average of the coherences, populations, and susceptibilities of Fourier components associated, calculated by the optical stochastic Bloch equations. These symmetry properties show the dependence of the measured spectra with the variations in the frequencies of the incident fields. Our results show that the inclusion of the thermal bath diminishes the intensity response as well it promotes the loss of the symmetry properties, compared with the same results in the absence of the bath.

SOLVENT COLLISIONAL EFFECTS IN FOUR-WAVE MIXING

2012 ◽  
Vol 21 (02) ◽  
pp. 1250016 ◽  
Author(s):  
A. MASTRODOMENICO ◽  
M. A. IZQUIERDO ◽  
J. L. PAZ
Keyword(s):  
Electromagnetic Field ◽  
Random Function ◽  
Molecular System ◽  
Relaxation Times ◽  
Four Wave Mixing ◽  
Collective Effects ◽  
Thermal Bath ◽  
Wave Mixing ◽  
Stochastic Effects ◽  
Upper Level

The stochastic effects of a thermal bath on a two-level molecular system interacting with a classical electromagnetic field are considered. The collective effects are modeled as a random Bohr frequency, whose manifestation is the broadening of the upper level according to a prescribed random function. A methodology based in cumulant expansions to obtain the average in the Fourier components associated with the coherence and populations, calculated by Optical Stochastic Bloch Equations (OSBE), is employed. The Four-wave mixing signal intensity as a function of the detuning of the pump beam, parametrized by the ratio of the relaxation times and other variables, is analyzed.

scholarly journals Velocity effect on the stimulated transition process of a multilevel atom in a thermal bath

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Huabing Cai
Keyword(s):  
Electromagnetic Field ◽  
Perturbation Theory ◽  
Transition Process ◽  
Stimulated Emission ◽  
Atomic Transition ◽  
Thermal Bath ◽  
Transition Rates ◽  
Atomic Polarizability ◽  
Velocity Effect ◽  
Multilevel Atom

AbstractThis paper investigates the stimulated transition process of a uniformly moving atom in interaction with a thermal bath of the quantum electromagnetic field. Using the perturbation theory, the atomic stimulated emission and absorption rates are calculated. The results indicate that the atomic transition rates depend crucially on the atomic velocity, the temperature of the thermal bath, and the atomic polarizability. As these factors change, the atomic stimulated transition processes can be enhanced or weakened at different degrees. In particular, slowly moving atoms in the thermal bath with high temperature ($$T\gg \omega _{0}$$ T ≫ ω 0 ) perceive a smaller effective temperature $$T \big ( 1-\frac{1}{10} v^{2} \big )$$ T ( 1 - 1 10 v 2 ) for the polarizability perpendicular to the atomic velocity or $$T \big ( 1-\frac{3}{10} v^{2} \big )$$ T ( 1 - 3 10 v 2 ) for the polarizability parallel to the atomic velocity. However, ultra-relativistic atoms perceive no influence of the background thermal bath. In turn, in terms of the atomic transition rates, this paper explores and examines the relativity of temperature of the quantum electromagnetic field.

An Emerging O(N) Model and Algorithm for Virtual Prototyping of Dynamics of Molecular Conformation

2008 ◽  
Author(s):  
Andrew Ries ◽  
Shanzhong Shawn Duan
Keyword(s):  
Degrees Of Freedom ◽  
Molecular Conformation ◽  
Molecular System ◽  
Equations Of Motion ◽  
Integration Step ◽  
Computational Costs ◽  
System A ◽  
Hard Constraints ◽  
Solution Of Equations ◽  
Computationally Intensive

Molecular dynamics is effective for nano-scale phenomenon analysis. There are two major computational steps associated with computer simulation of dynamics of molecular conformation and they are the calculation of the interatomic forces and the formation and solution of the equations of motion. Currently, these two computational steps are treated separately, but in this paper an O(N) (order N) procedure is presented for an integration between these computational steps. For computational costs associated with calculating the interatomic forces, an internal coordinate method (ICM) approach is used for determining potentials due to both the bonding and non-bonding interactions. Thus, the potential gradients can be expressed as a combination of the potential in absolute and relative coordinates. For computational costs associated with the formation and solution of the equations of motion for the system, a constraint method that is used in computational multibody dynamics is utilized. This frees some degrees of freedom so that Kane’s method can be applied for the recursive formation and solution of equations of motion for the atomistic molecular system. Because the inclusion of lightly excited high frequency degrees of freedom, such as inter-atomic oscillations and rotation about double bonds would force the use of very small integration step sizes, holonomic constraints are introduced to freeze these “uninteresting” degrees of freedom. By introducing these hard constraints the time scale can be appropriately sized for to provide a less computationally intensive dynamic simulation of molecular conformation. The algorithm developed improves computational speed significantly when compared with any traditional O(N3) procedure.

scholarly journals Gauge-independent Theory of Symmetry. I.

1964 ◽  
Vol 17 (4) ◽  
pp. 431 ◽  
Author(s):  
LJ Tassie ◽  
HA Buchdahl
Keyword(s):  
Electromagnetic Field ◽  
Single Particle ◽  
Equations Of Motion ◽  
Classical Mechanics ◽  
Conserved Quantities ◽  
Continuous Symmetry ◽  
Symmetry Properties ◽  
Symmetry Transformations ◽  
Hamiltonian Forms

The invariance of a system under a given transformation of coordinates is usually taken to mean that its Lagrangian is invariant under that transformation. Consequently, whether or not the system is invariant will depend on the gauge used in describing the system. By defining invariance of a system to mean the invariance of its equations of motion, a gauge-independent theory of symmetry properties is obtained for classical mechanics in both the Lagrangian and Hamiltonian forms. The conserved quantities associated with continuous symmetry transformations are obtained. The system of a single particle moving in a given electromagnetic field is considered in detail for various symmetries of the electromagnetic field, and the appropriate conserved quantities are found.

scholarly journals AN EXACT SOLUTION TO THE QUANTIZED ELECTROMAGNETIC FIELD IN D-DIMENSIONAL DE SITTER SPACE–TIMES

2012 ◽  
Vol 27 (30) ◽  
pp. 1250177 ◽  
Author(s):  
G. ALENCAR ◽  
I. GUEDES ◽  
R. R. LANDIM ◽  
R. N. COSTA FILHO
Keyword(s):  
Electromagnetic Field ◽  
Extra Dimensions ◽  
Particle Production ◽  
De Sitter Space ◽  
Thermal Bath ◽  
De Sitter ◽  
Microwave Background ◽  
Quantum Behavior ◽  
Dynamic Invariants ◽  
Do So

In this work, we investigate the quantum theory of light propagating in D-dimensional de Sitter space–times. To do so, we use the method of dynamic invariants to obtain the solution of the time-dependent Schrödinger equation. The quantum behavior of the electromagnetic field in this background is analyzed. As the electromagnetism loses its conformality in D≠4, we point out that there will be particle production and comoving objects will feel a Bunch–Davies thermal bath. This may become important in extra dimension physics and raises the intriguing possibility that precise measurements of the Cosmic Microwave Background could verify the existence of extra dimensions.

Solvent effects in the nonlinear optical properties using the Voigt function

2016 ◽  
Vol 25 (02) ◽  
pp. 1650016 ◽  
Author(s):  
J. L. Paz ◽  
Luis G. Rodríguez ◽  
Juan F. Cárdenas ◽  
Cesar Costa-Vera
Keyword(s):  
Optical Properties ◽  
Solvent Effects ◽  
Nonlinear Optical ◽  
Molecular System ◽  
Random Variable ◽  
Nonlinear Optical Properties ◽  
Thermal Bath ◽  
Gaussian Distributions ◽  
Radiative Interaction ◽  
Voigt Function

Nonlinear optical properties of a two-level molecular system immersed in a thermal bath have been studied in the present work. Solvent effects were explicitly considered by modeling the non-radiative interaction with the solute as a random variable. The innovation of this treatment is that it allows us to take into account the environment, inducing quantum effects not considered by classical treatment. The major contribution of the methodology proposed in this work, is the implementation of an approximant to the Voigt function as a probability distribution, because it allow us to cover a wider range of possible interactions among the solvent and the molecular system by simple changing the parameters [Formula: see text] and [Formula: see text], associated to the variances of the Lorentzian and Gaussian distributions, respectively.

Online single-shot pulse reconstruction for optimizing a seeded X-ray free-electron laser

2020 ◽  
Author(s):  
Li Zeng ◽  
Duan Gu ◽  
Chao Feng ◽  
Bo Liu ◽  
Zhentang Zhao
Keyword(s):  
Free Electron ◽  
Molecular System ◽  
Single Shot ◽  
X Ray ◽  
System A ◽  
Precise Knowledge ◽  
Longitudinal Profiles ◽  
Temporal Profiles ◽  
And Control ◽  
First Time

Abstract X-ray free-electron lasers (FELs) hold promising prospects for opening up opportunities for ultra-fast sciences at the atomic and molecular system. A precise knowledge of temporal information of FEL pulses is the central issue for experiments. Here we demonstrated an online diagnostic method to determine the FEL temporal profiles at the Shanghai Soft X-ray FEL facility. This robust method, designed for seeded FELs, allows researchers to acquire real-time longitudinal profiles of FEL pulses with a resolution better than 3fs. Based on this method, for the first time, we can directly observe the generation and evolution of a seeded FEL online. This helps us to further understand the physics and realize the lasing of a stable, nearly fully coherent soft X-ray FEL through a two-stage harmonic up-shift configuration. This method also provides an intuitive way for precise detection and control of the relative timing between electron beams and external optical lasers.

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