Low-frequency Photons Research Articles

Tunneling into the A15 compounds

Electron tunneling has been extensively studied on the high- T c A15 compounds including Nb 3 Sn, Nb 3 Al and Nb 3 Ge to assess their superconducting properties as well as material characteristics. High-quality A15 tunnel junctions were fabricated routinely by the use of oxidized amorphous Si barriers, and homogeneous samples of the unstable A15 materials were prepared by the controlled film synthesis of e-beam coevaporation. A modified gap inversion analysis which includes the effect of a proximity layer near the film surface generated consistent solutions of α 2 F ( ω ) and other microscopic parameters. A common trend observed in these high- T c materials is that the low-frequency photon strengths in the α 2 F ( ω ) tend to be strongly enhanced as their compositions approach the A15 phase boundaries.

Low-frequency photons in processes involving particles with spin

Low-frequency photons in processes involving particles with spin

Two-photon resonance fluorescence

The excitation spectrum of a two-level atom interacting with a strong electromagnetic field is considered when the atomic transition frequency is nearly twice the frequency of the laser field. The spectral function consists of four Lorentzian lines describing: the central line peaked near the two-photon resonance, two sidebands peaked at the high and low frequency regions respectively and the one-photon frequency mode. In the limit of high photon densities, the low frequency photon mode is induced by the pump field which removes the singularity occurring at the two-photon resonance frequency.

1/f Macroscopic Quantum Fluctuations of Elec- tric Currents Due to Bremsstrahlung with Infra- red Radiative Corrections

Due to interaction with the quantized electromagnetic field, any current carrier involved in some scattering process may emit low frequency photons. This photon emission carries negligible energy but modulates the current nevertheless, resulting in 1/f and 1/Δf noise

Quantum theory of 1/ƒ noise

Due to interaction with the quantized electromagnetic field, any current carrier involved in some scattering process may emit low frequency photons. This photon emission carries neglible energy but modulates the current nevertheless, resulting in 1/ƒ and 1/Δƒ noise.

Slowly braked, rotating neutron stars

view Abstract Citations (1) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Slowly braked, rotating neutron stars. Sato, H. Abstract A slowly braked, rotating neutron star is believed to be a star which rapidly rotates, has no nebula, is nonpulsing, and has a long initial braking time of ten thousand to a million years because of a low magnetic field. Such an object might be observable as an extended weak source of infrared or radio wave radiation due to the scattering of low-frequency strong-wave photons by accelerated electrons. If these objects exist abundantly in the Galaxy, they would act as sources of relatively low-energy cosmic rays. Pulsars (rapidly braked neutron stars) are shown to have difficulties in providing an adequate amount of cosmic-ray matter, making these new sources seem necessary. The possibility that the acceleration mechanism around a slowly braked star may be not a direct acceleration by the strong wave but an acceleration due to plasma turbulence excited by the strong wave is briefly explored. It is shown that white dwarfs may also be slowly braked stars with braking times longer than 3.15 million years. Publication: The Astrophysical Journal Pub Date: February 1975 DOI: 10.1086/153376 Bibcode: 1975ApJ...195..743S Keywords: Astronomical Models; Cosmic Rays; Neutron Stars; Pulsars; Stellar Evolution; Stellar Rotation; Braking; Gravitational Collapse; Milky Way Galaxy; Particle Acceleration; Stellar Radiation; White Dwarf Stars; Astrophysics full text sources ADS |

Low-frequency photon scattering by nuclei

We study the low-frequency limit of elastic photon scattering by nuclei of spin zero. We calculate the energy independent cross section (Thomson scattering) and the term quadratic in the frequency (Rayleigh scattering) in two ways: within classical electrodynamics and non-relativistic quantum mechanics. Particular emphasis is put on a correct description of the c.m. motion. The origin of the various retardation and polarizability terms is discussed. They are related to polarizabilities in static external fields. We propose the existence of a diaelectric polarizability which is the electric counterpart of diamagnetism. Orders of magnitudes of the expected effects are given.

The flow of ionized gas from a globule in interstellar space

The flow of ionized gas from a globule in interstellar space illustrates rather well the various physical processes that often occur in or near ionization fronts. Thus the non-ionized gas is largely shielded from the incident radiation by the HII region that forms around it. The low frequency photons are absorbed more easily in this region so that the typical photon reaching the front has more than average energy, and the usual processes govern the thermal balance of the gas. In the case of a globule the front is strong D type, so that it advances subsonically into the gas ahead of it, but the ionized gas streams away supersonically in the rear. The strong D condition provides one of the boundary conditions needed to define the flow; this conclusion is similar to one reached by Axford 6) when he was studying the expansion of a spherically symmetrical HII region around a star. Finally some estimates are made for the mass of gas likely to be contained in the globule, and of the condition for it to be stable against gravitational collapse.

The Decay of Resonance Radiation by Spontaneous Emission

A critical examination of the theory of resonance radiation has been carried through, employing the mathematical technique of Laplace and Stieltjes transforms. Particular attention has been devoted to the question of the temporal behavior of the excited state. With no restrictions on the interaction between atom and radiation field other than that it be real, and that processes of sufficiently high frequency contribute only negligible effects, one can prove that the probability amplitude of the excited state cannot decay according to the general law ${\ensuremath{\Sigma}}_{\ensuremath{\mu},\ensuremath{\nu}}{C}_{\ensuremath{\mu}\ensuremath{\nu}}{t}^{{\ensuremath{\lambda}}_{\ensuremath{\mu}}}{e}^{\ensuremath{-}{\ensuremath{\beta}}_{\ensuremath{\nu}}t},$ where the ${\ensuremath{\lambda}}_{\ensuremath{\mu}}$ and ${\ensuremath{\beta}}_{\ensuremath{\nu}}$ are complex constants lying in the right half-plane and the ${C}_{\ensuremath{\mu}\ensuremath{\nu}}$ are arbitrary complex coefficients. The deviation from the law just cited can be termed a straggling phenomenon since exact analysis shows that the probability amplitude, for sufficiently long times, is greater than that defined according to the radioactive decay law.Rigorous analysis of the source of this apparently anomalous behavior reveals the following explanation. Although the probability amplitude of the excited state is, strictly speaking, a functional of the interaction between the transition current in the atom and the photon states of the electromagnetic field, the essential features are determined principally by those states lying near the resonance frequency. Three elementary observations are immediately apparent. First, a particularly tractable analytical approximation for the interaction can be made such that the value of the actual interaction is reproduced at the resonance frequency and such that the behavior for high and low frequency photon states is at least qualitatively correct. Exact solutions in closed form can be obtained for this interaction. Second, in terms of the preceding representation it is possible to show that, associated with the transition between two atomic states, one is presented with a concomitant picture of a damped oscillation of charge describable in purely classical terms. Third, this classical motion can be interpreted as forming a source function for a continuous stochastic process in terms of which one finally derives the representation of the probability amplitude of the excited state. The straggling phenomenon previously cited is therefore that associated with all diffusion processes. The consideration of the exact interaction leads to more involved diffusion phenomena but does not in any case permit a radioactive decay law.

Radiative Reaction and Damping in Scattering

The higher order radiative corrections and the damping corrections to the cross section for the scattering of an electron by an electrostatic potential are investigated. It is shown that the perturbation treatment of the radiative corrections at high frequencies joins on to the Bloch-Nordsieck solution for low frequencies. The damping effect arising from the low frequency photons is shown to be negligible, and a modified damping equation is proposed which gives a smooth transition to the damping correction in passing from high to low frequency photons

Compton Scattering and the Emission of Low Frequency Photons

According to the perturbation theory of the scattering of photons, the cross section for Compton scattering diverges, owing to the multiple scattering effects for low frequency photons. It is shown that by the application of the method of Block and Nordsieck this difficulty can be evaded, and that, to a first approximation, the cross section for Compton scattering is given by the Klein-Nishina formula.