A.F. Borghesani
- Published in print:
- 2007
- Published Online:
- January 2008
- ISBN:
- 9780199213603
- eISBN:
- 9780191707421
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199213603.003.0025
- Subject:
- Physics, Condensed Matter Physics / Materials
This chapter explains why the dynamics and evolution of the formation of electron bubbles has been investigated by looking at how the electron mobility changes as a function of the density of helium ...
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This chapter explains why the dynamics and evolution of the formation of electron bubbles has been investigated by looking at how the electron mobility changes as a function of the density of helium gas.Less
This chapter explains why the dynamics and evolution of the formation of electron bubbles has been investigated by looking at how the electron mobility changes as a function of the density of helium gas.
A.F. Borghesani
- Published in print:
- 2007
- Published Online:
- January 2008
- ISBN:
- 9780199213603
- eISBN:
- 9780191707421
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199213603.003.0026
- Subject:
- Physics, Condensed Matter Physics / Materials
The phenomenon of self-trapping is well known in helium and in different systems, such as electrons in ammonia, Positronium in dense helium gas, and so on. It is known that localization occurs when ...
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The phenomenon of self-trapping is well known in helium and in different systems, such as electrons in ammonia, Positronium in dense helium gas, and so on. It is known that localization occurs when the balance between exchange repulsive forces, thermal energy, expansion work, and polarization energy is such that the excess free energy of the localized state is lower than that of the extended state. Several physical mechanisms have been proposed to explain how the electron bubble forms, including trapping on virtual or resonant states due to density fluctuations. Stabilization of the localized state is obtained by sound wave emission of the new-born, oscillating bubble. The breathing mode of the cavity around an helium excimer in liquid helium has been also measured.Less
The phenomenon of self-trapping is well known in helium and in different systems, such as electrons in ammonia, Positronium in dense helium gas, and so on. It is known that localization occurs when the balance between exchange repulsive forces, thermal energy, expansion work, and polarization energy is such that the excess free energy of the localized state is lower than that of the extended state. Several physical mechanisms have been proposed to explain how the electron bubble forms, including trapping on virtual or resonant states due to density fluctuations. Stabilization of the localized state is obtained by sound wave emission of the new-born, oscillating bubble. The breathing mode of the cavity around an helium excimer in liquid helium has been also measured.
A.F. Borghesani
- Published in print:
- 2007
- Published Online:
- January 2008
- ISBN:
- 9780199213603
- eISBN:
- 9780191707421
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199213603.003.0027
- Subject:
- Physics, Condensed Matter Physics / Materials
Experiments on the mobility of electrons in dense helium gas elucidated how localized electron states develop when the gas density gas is increased. Up to 77 K, the density dependence of the mobility ...
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Experiments on the mobility of electrons in dense helium gas elucidated how localized electron states develop when the gas density gas is increased. Up to 77 K, the density dependence of the mobility clearly shows that the formation of electron bubbles is a continuous phenomenon. Localization of electrons in bubbles also appears at high temperatures if the density is so large that the free energy of the localized state is negative enough. Percolation and hydrodynamic models have been devised to explain the continuous transition from high-mobility states to low-mobility states. It is shown that density-dependent, quantum multiple scattering effects modify the energy of the nearly free electron in a way that can be accurately described by heuristically modifying the kinetic theory prediction.Less
Experiments on the mobility of electrons in dense helium gas elucidated how localized electron states develop when the gas density gas is increased. Up to 77 K, the density dependence of the mobility clearly shows that the formation of electron bubbles is a continuous phenomenon. Localization of electrons in bubbles also appears at high temperatures if the density is so large that the free energy of the localized state is negative enough. Percolation and hydrodynamic models have been devised to explain the continuous transition from high-mobility states to low-mobility states. It is shown that density-dependent, quantum multiple scattering effects modify the energy of the nearly free electron in a way that can be accurately described by heuristically modifying the kinetic theory prediction.
Guang S. He
- Published in print:
- 2014
- Published Online:
- December 2014
- ISBN:
- 9780198702764
- eISBN:
- 9780191772368
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198702764.003.0006
- Subject:
- Physics, Atomic, Laser, and Optical Physics
The intense coherent light-induced refractive-index change of a nonlinear medium may lead to several effects on the incident light itself. A laser beam with a non-uniform transverse intensity ...
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The intense coherent light-induced refractive-index change of a nonlinear medium may lead to several effects on the incident light itself. A laser beam with a non-uniform transverse intensity distribution can induce a transversely non-uniform refractive-index change in the nonlinear medium, which in turn may affect the shape and spatial structure of the laser beam. This leads to self-focusing, self-defocusing, or self-trapping effects. If the incident beam consists of short or ultrashort laser pulses, the pulsed change of light intensity may cause a fast variation of the phase encountered by the pulsed beam. This is the so-called self-phase modulation effect. According to the principle of Fourier transform, a fast phase modulation will cause a broadening of the frequency spectrum. This is the so-called spectral self-broadening effect. Self-focusing is the basic mechanism for spatial solitons, self-phase-modulation is the basic mechanism for temporal solitons, and spectral self-broadening is the basic mechanism for supercontinuum generation.Less
The intense coherent light-induced refractive-index change of a nonlinear medium may lead to several effects on the incident light itself. A laser beam with a non-uniform transverse intensity distribution can induce a transversely non-uniform refractive-index change in the nonlinear medium, which in turn may affect the shape and spatial structure of the laser beam. This leads to self-focusing, self-defocusing, or self-trapping effects. If the incident beam consists of short or ultrashort laser pulses, the pulsed change of light intensity may cause a fast variation of the phase encountered by the pulsed beam. This is the so-called self-phase modulation effect. According to the principle of Fourier transform, a fast phase modulation will cause a broadening of the frequency spectrum. This is the so-called spectral self-broadening effect. Self-focusing is the basic mechanism for spatial solitons, self-phase-modulation is the basic mechanism for temporal solitons, and spectral self-broadening is the basic mechanism for supercontinuum generation.
Lev Pitaevskii and Sandro Stringari
- Published in print:
- 2016
- Published Online:
- March 2016
- ISBN:
- 9780198758884
- eISBN:
- 9780191818721
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198758884.003.0015
- Subject:
- Physics, Condensed Matter Physics / Materials
This chapter discusses several phenomena related to the coherence of trapped Bose–Einstein condensates. These include the long-range behaviour of the one-body density matrix and the interference ...
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This chapter discusses several phenomena related to the coherence of trapped Bose–Einstein condensates. These include the long-range behaviour of the one-body density matrix and the interference fringes exhibited by two expanding condensates overlapping in space. Interference patterns in the momentum distribution are also discussed. A special section is devoted to the Josephson oscillations in the double-well potential, including the plasma oscillation and self-trapping phenomena. The procedures required to quantize the Josephson Hamiltonian, the phenomena of decoherence and fluctuations of the phase, and the derivation of the Bose–Hubbard model in the problem of the double well, are also discussed.Less
This chapter discusses several phenomena related to the coherence of trapped Bose–Einstein condensates. These include the long-range behaviour of the one-body density matrix and the interference fringes exhibited by two expanding condensates overlapping in space. Interference patterns in the momentum distribution are also discussed. A special section is devoted to the Josephson oscillations in the double-well potential, including the plasma oscillation and self-trapping phenomena. The procedures required to quantize the Josephson Hamiltonian, the phenomena of decoherence and fluctuations of the phase, and the derivation of the Bose–Hubbard model in the problem of the double well, are also discussed.
