Far infrared impurity absorption in a quantum well

We have calculated the energy and lineshape of the 1s → 2p_x,y transition for a hydrogenic impurity located in a quantum well. Due to the dependence of the transition energy on the impurity location, the absorption lineshape is very sensitive to the doping profile. The spectrum, in general, exhibits two peaks, arising from impurities located near the center and the edges of the well.     

Mechanism for far infrared absorption of small metallic particles

A mechanism for far infrared absorption of small particles of noble metals is described. The electric double layer formed at the particle surface allows excitation of the resonant low frequency mode in which the metal core oscillates rigidly with respect to the shellof adsorbed atoms. The model is capable of explaining the large magnitude and the anomalous frequency dependence recently reported for Pt particles.     

Far infrared multiphoton absorption in p-Ge

We have calculated the far infrared multiphoton absorption coefficient in p-Ge for three different temperatures. It is shown that, under high radiation intensity, the rate of increase of the absorption coefficient changes strongly with intensity as a result of the Stark effect.     

Optical absorption in ultrafine gold particles

Optical absorption of ultrafine, gas evaporated gold particles (diameters 3—4 nm) has been measured in the wavelength interval 0.3—2.5 μm. The data agree well with the Maxwell-Garnett theory in conjunction with optical constants for bulk Au, provided these are modified to incorporate the effect of size dependent electron scattering.     

Far infrared optical excitation in metallic uranium sulfide

Previous near normal incidence reflectivity measurements on US single crystals from 12 to 0.03 eV have been extended down to 0.0018 eV (15 cm^?1). A broad plateau with a reflectivity of 90±2% is observed between 40 and 400 cm^?1 with a further increase of the reflectivity below 40 cm^?1. A Kramers-Kronig transformation of the data shows the existence of a resonance at 315 cm^?1. From a comparison with recent neutron data and other arguments we deduce that this resonance is due to the excitation of a transverse optical phonon coupled to an f→d or d→f interband transition.     

Generalized entropies in quantum and classical statistical theories

We study a version of the generalized (h, ?)-entropies, introduced by Salicrú et al. [M. Salicrú et al., Commun. Stat. Theory Method. 22, 2015 (1993)], for a wide family of probabilistic models that includes quantum and classical statistical theories as particular cases. We extend previous works by exploring how to define (h, ?)-entropies in infinite dimensional models.     

Far infrared absorption of a-Ge and a-Ge-Ga alloys

We have studied the absorption of amorphous germanium and amorphous germanium-gallium alloys in the far infrared phonon absorption region. The results have been obtained using a new technique which is particularly suited to the use of thin samples and has provided data free from the interference effects which have plagued other workers. We discuss the absorption mechanism is terms of the charges associated with the structural defects and the gallium acceptor states.     

Far infrared absorption in bulk amorphous red phosphorous

Far infrared absorption measurements have been performed above 30 cm^?1 in bulk amorphous red P at 300 K. A number of low frequency spectral features are observed that are not present in the corresponding bulk amorphous As spectrum. Deep minima observed at 163 and 320 cm^?1 in α(ω) and in the Raman spectra suggest that the phonon density of states is essentially divided into 3 bands. A calculation of the mean effective charge of the bands indicates weak coupling to the lowest frequency band. A comparison with the results in a-As suggests a less rapid frequency variation in the infrared coupling parameter at low frequencies in a-$\text{P}$.     

Far infrared absorption of amorphous GaAs and Ge

Far infrared reflection spectra of amorphous GaAs and Ge have been obtained in the frequency region from 30–600 cm^?1. For each material, curves of ω?₂ vs frequency have been obtained whose corresponding reflectivity curves give a best fit to the data. The peak value of the abdorption coefficient is about 4000 cm^?1 for GaAs and 160 cm^?1 for Ge. The results are compared with Raman spectra and with theoretical calculations.     

Far infrared absorption by acceptor states in tellurium

Transmission spectra of slightly antimony-doped tellurium were measured at 2K. Absorptions due to transitions of holes from the acceptor ground state to the excited state and to the valence band were observed. Reflecting the double-maximum structure of the valence band, the ground state splits into two levels, the binding energies of which are found to be 1.31 and 1.47 meV, respectively.     

Renarks on the classical limit of quantum field theories

Recently, there has been an increasing interest in computing quantum mechanical corrections to solutions of classical field equations. In this note, we want to proceed in the opposite way and we summarize theorems about the classical limit of relativistic quantum field models. These results are a byproduct of the so called constructive approach to quantum field theory.After a section on generalities, we discuss in Section 2 the situation where no phase transitions occur in the limith0 and in Section 3 we reformulate one result in the case where such a transition occurs (Glimmet al. [7]). We discuss the validity of the loop expansion. It seems however that the tools to show the rigorous validity of soliton calculations are not yet prepared.     

Far infrared absorption by pure and hydrogenated amorphous silicon

Measurements of the far infrared absorption coefficient of pure and hydrogenated a-Si are reported. The results are similar to earlier data on pure a-Si though we find different relative strengths of the three absorption bands. The present data are sufficiently accurate at low frequencies to observe structure on the lowest frequency peak, and the behaviour of this upon hydrogenation is consistent with the charged void model proposed earlier.     

Comparison between the classical and quantum theories of incoherent scattering

Acta physica Academiae Scientiarum Hungaricae - The incoherent scattering of light by a volume of gas can be treated by classical methods in a straightforward manner. Certain difficulties are...     

Fundamental theories of waves and particles formulated without classical mass

Quantum and classical mechanics are two conceptually and mathematically different theories of physics, and yet they do use the same concept of classical mass that was originally introduced by Newton in his formulation of the laws of dynamics. In this paper, physical consequences of using the classical mass by both theories are explored, and a novel approach that allows formulating fundamental (Galilean invariant) theories of waves and particles without formally introducing the classical mass is presented. In this new formulation, the theories depend only on one common parameter called ‘wave mass’, which is deduced from experiments for selected elementary particles and for the classical mass of one kilogram. It is shown that quantum theory with the wave mass is independent of the Planck constant and that higher accuracy of performing calculations can be attained by such theory. Natural units in connection with the presented approach are also discussed and justification beyond dimensional analysis is given for the particular choice of such units.     

Size effects in the optical absorption of ultrafine aluminium particles

Parallel band absorption at 1.55 eV, which is clearly seen in bulk aluminium, becomes much less visible in transmittance spectra on films consisting of gas evaporated particles with diameters of 3 to 4 nm. This can be understood, at least partially, from an enhancement of the Drude absorption caused by the lowered electron lifetime.     

Stochastic theory for classical and quantum mechanical systems

We formulate from first principles a theory of stochastic processes in configuration space. The fundamental equations of the theory are an equation of motion which generalizes Newton's second law and an equation which expresses the condition of conservation of matter. Two types of stochastic motion are possible, both described by the same general equations, but leading in one case to classical Brownian motion behavior and in the other to quantum mechanical behavior. The Schrödinger equation, which is derived here with no further assumption, is thus shown to describe a specific stochastic process. It is explicitly shown that only in the quantum mechanical process does the superposition of probability amplitudes give rise to interference phenomena; moreover, the presence of dissipative forces in the Brownian motion equations invalidates the superposition principle. At no point are any special assumptions made concerning the physical nature of the underlying stochastic medium, although some suggestions are discussed in the last section.     

The concept of indistinguishable particles in classical and quantum physics

The consequences of the following definition of indistinguishability are analyzed. Indistinguishable classical or quantum particles are identical classical or quantum particles in a state characterized by a probability measure, a statistical operator respectively, which is invariant under any permutation of the particles. According to this definition the particles of classical Maxwell-Boltzmann statistics are indistinguishable.     

The effect of shape and size on the electronic properties of ultrafine metallic particles

The subject of ultrafine metallic particles is treated with emphasis on energy level statistics. The energy level statistics so far proposed are reviewed based on the effect of shape of particles. The deviation of the nature of the chemical bond and that of magnetic properties in small size systems from those of bulk is described. The relevant electronic properties are expressed by formulae that incorporate the effect of shape in addition to size. New and old experiments including NMR Knight shift and static magnetic susceptibility are analyzed by means of the proposed formulae. The shape of particles is discussed in connection with the preparation methods. A concept of “the degree of metallicity” is introduced to characterize the statistics of level spacing fluctuation of small metal particles. A number of electronic properties of small size materials are also explained in terms of their sizes. The systems examined are small particles and conjugated chain compounds. The concept of zero-dimensionality is proposed and it is correlated with certain conservation laws such as topological invariance (conservation of shape) and as a conservation of the number of spins (parity of electrons).     

Unification of the quantum and classical theories of methyl NMR.

The existing low and high temperature theories of methyl NMR are not linked because two conditions imposed on state functions in the low temperature theory are not compatible with the classical rotations on which the high temperature theory is based. The conditions do not occur in a geometrical theory of quantum phenomena in which particles and waves have separate roles. When applied to methyl dynamics, this theory covers the whole temperature range.