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Results for “Classical and quantum mechanics”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very loud incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering weave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts the exchange approximation has only been considered. We calculate the laser assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

Bhatia, A. K.↗
NASA NTRS2009

Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very low incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it The scattering wave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts, the exchange approximation has only been considered. We calculate the laser-assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

Bhatia, Anand K.↗
NASA NTRS2012

Free-Free Transitions in the Presence of Laser Fields and Debye Potential at Very Low Incident Electron Energies

We study the free-free transition in electron-helium ion in the ground state and embedded in a Debye potential in the presence of an external laser field at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen as monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function for it. The scattering wave function for the incident electron on the target embedded in a Debye potential is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transition for absorption/emission of a single photon or no photon exchange. The results will be presented at the conference.

Bhatia, Anand↗
NASA NTRS2005

Bidirectional Classical Stochastic Processes with Measurements and Feedback

A measurement on a quantum system is said to cause the "collapse" of the quantum state vector or density matrix. An analogous collapse occurs with measurements on a classical stochastic process. This paper addresses the question of describing the response of a classical stochastic process when there is feedback from the output of a measurement to the input, and is intended to give a model for quantum-mechanical processes that occur along a space-like reaction coordinate. The classical system can be thought of in physical terms as two counterflowing probability streams, which stochastically exchange probability currents in a way that the net probability current, and hence the overall probability, suitably interpreted, is conserved. The proposed formalism extends the . mathematics of those stochastic processes describable with linear, single-step, unidirectional transition probabilities, known as Markov chains and stochastic matrices. It is shown that a certain rearrangement and combination of the input and output of two stochastic matrices of the same order yields another matrix of the same type. Each measurement causes the partial collapse of the probability current distribution in the midst of such a process, giving rise to calculable, but non-Markov, values for the ensuing modification of the system's output probability distribution. The paper concludes with an analysis of a classical probabilistic version of the so-called grandfather paradox.

Hahne, G. E.↗
NASA NTRS2014

Kuang's Semi-Classical Formalism for Calculating Electron Capture Cross Sections: A Space- Physics Application

Accurate estimates of electroncapture cross sections at energies relevant to the modeling of the transport, acceleration, and interaction of energetic neutral atoms (ENA) in space (approximately few MeV per nucleon) and especially for multi-electron ions must rely on detailed, but computationally expensive, quantum-mechanical description of the collision process. Kuang's semi-classical approach is an elegant and efficient way to arrive at these estimates. Motivated by ENA modeling efforts for apace applications, we shall briefly present this approach along with sample applications and report on current progress.

Barghouty, A. F.↗
NASA NTRS2012

Kuang's Semi-Classical Formalism for Electron Capture Cross-Sections in Ion-Ion Collisions at few MeV's/nucleon: Application to ENA Modeling

Accurate estimates of electron-capture cross sections at energies relevant to energetic neutral atom (ENA) modeling (approx few MeV per nucleon) and for multi-electron ions must rely on first-principles approaches and/or detailed quantum-mechanical simulation of the collision process. Kuang's semi-classical approach offers a middle-ground, elegant and efficient way to arrive at these estimates. We shall present a sample application and current progress in applying and extending Kuang's formalism to ENA modeling.

Barghouty, A. F.↗
NASA NTRS2007

Can the Hypothesis 'Photon Interferes only with Itself' be Reconciled with Superposition of Light from Multiple Beams or Sources?

Any superposition effect as measured (SEM) by us is the summation of simultaneous stimulations experienced by a detector due to the presence of multiple copies of a detectee each carrying different values of the same parameter. We discus the cases with light beams carrying same frequency for both diffraction and multiple beam Fabry-Perot interferometer and also a case where the two superposed light beams carry different frequencies. Our key argument is that if light really consists of indivisible elementary particle, photon, then it cannot by itself create superposition effect since the state vector of an elementary particle cannot carry more than one values of any parameter at the same time. Fortunately, semiclassical model explains all light induced interactions using quantized atoms and classical EM wave packet. Classical physics, with its deeper commitment to Reality Ontology, was better prepared to nurture the emergence of Quantum Mechanics and still can provide guidance to explore nature deeper if we pay careful attention to successful classical formulations like Huygens-Fresnel diffraction integral.

Roychoudhuri, Chandrasekhar↗
NASA NTRS1972

Electron impact ionization of H

The results of theoretical calculations for the reactions between electrons and negative hydrogen atoms are discussed for an electron colliding with a negative hydrogen ion and neutralizing the hydrogen ion by stripping the loosely bound electron from it, and the two free electrons moving away. A semi-quantum description of the process is presented in which the target is described in terms of quantum mechanics, and the projectile electron is described in a classical fashion.

Faisal, F. H. M.↗
NASA NTRS1985

Collisional excitation of molecules in dense interstellar clouds

State transitions which permit the identification of the molecular species in dense interstellar clouds are reviewed, along with the techniques used to calculate the transition energies, the database on known molecular transitions and the accuracy of the values. The transition energies cannot be measured directly and therefore must be modeled analytically. Scattering theory is used to determine the intermolecular forces on the basis of quantum mechanics. The nuclear motions can also be modeled with classical mechanics. Sample rate constants are provided for molecular systems known to inhabit dense interstellar clouds. The values serve as a database for interpreting microwave and RF astrophysical data on the transitions undergone by interstellar molecules.

Green, S.↗
NASA NTRS1996

Sharp Infrared Eyes The Journey of QWIPs from Concept to Large Inexpensive Sensitive Arrays in Hand-held Infrared Cameras

One of the simplest device realizations of the classic particle-in-a-box problem of basic quantum mechanics is the Quantum Well Infrared Photodetector (QWIP). Optimization of the detector design and material growth and processing has culminated in the realization of a camera with a large (256x256 pixel) focal plane array of QWIPs which can see at 8.5 mu m, holding forth great promise for a variety of applications in the 6-25 mu m wavelength range.

Quantum Well Infrared Photodetector QWIP quantum m↗
NASA NTRS1996

Long Wavelength Quantum Well Infrared Photodetector (QWIP) Research at Jet Propulsion Laboratory

One of the simplest device realizations of the classic particle-in-the-box problem of basic quantum mechanics is the Quantum Well Infrared Photodetector (QWIP). Optimization of the detector design and material growth and processing has culminated in the realization of a 15 ??utoff 128x128 focal plane array camera and a camera with large (256x256 pixel) focal plane array of QWIPs which can see at 8.5 ??holding forth great promise for a variety of applications in the 6-25 ??avelength range. This paper discusses the physics of the QWIP and QWIP technology development at Jet Propulsion Laboratory

QWIP↗
NASA NTRS1998

Recent Progress in Quantum Well Infrared Photodetector Research and Development at Jet Propulsion Laboratory

One of the simplest device realizations of the classic particle-in-the-box problem of basic quantum mechanics is the Quantum Well Infrared Photodetector (QWIP). In this paper we discuss the optimization of the detector design, material growth and processing that has culminated in realization of 15 micron cutoff 128x128 QWIP focal plane array camera, hand-held and palmsize 256x256 long-wavelength QWIP cameras and 648x480 long-wavelength cameras, holding forth great promise for myriad applications in 6-25 micron wavelength range in science, medicine, defense and industry.

quantum↗
NASA NTRS2023

Independent Panel Report for Technical Assessment of NASA and External Quantum Sensing Capabilities

Sensors based on quantum mechanical properties of electromagnetic radiation and matter offer unique capabilities and performance sometimes difficult to achieve using classical approaches. This report assesses the suitability of quantum sensing for current and future NASA needs, with a specific focus on NASA’s Science Mission Directorate (SMD). Measurement and sensing needs across NASA SMD are reviewed as a driver for the possible incorporation of existing quantum sensors into the NASA portfolio and the development of next-generation quantum sensors. A range of quantum sensing modalities is then described and the current state of the art for each sensor is presented. Current research and development activities on quantum sensing within NASA are compared with the range of activities ongoing throughout the broader scientific community, both within the United States and internationally. In conclusion, there is considerable advantage to be gained by NASA from quantum sensors through the growth of internal programs and collaboration with outside entities.

Quantum Sensing↗
NASA NTRS1985

The Hanle effect applied to magnetic field measurements

The Hanle effect is the modification by a local magnetic field of the polarization due to coherent scattering in spectral lines. It results from the precession of a classical oscillator about the magnetic field direction. The sophisticated quantum-mechanical treatment, which is required to compute the polarization parameters of scattered light, was developed. The main features of the Hanle effect concerning magnetic field measurements are: (1) a good sensitivity within the approximate range 0.1 B gamma rho to 10 B gamma rho where B gamma rho is the field strength yielding a Larmor period equal to the radiative lifetime, (2) there is no Hanle effect for field vectors parallel to the excitating beam, (3) the Hanle effect refers essentially to the linear polarization in a spectral line, (4) various points in the line profile are affected in the same way by change of linear polarization so that polarization parameters can be measured on the integrated line profile.

Leroy, J. L.↗