Abstract: 1. Electrons, photons and atoms. 2. The elements of quantum mechanics. 3. One-electron atoms. 4. Interaction of one-electron atoms with electromagnetic radiation. 5. One-electron atoms: fine structures and interactions with external electric and magnetic fields. 6. Two-electron atoms. 7. Many-electron atoms. 8. The interaction of many-electron atoms with electromagnetic fields. 9. Molecular structure. 10. Molecular spectra. 11. Atomic collisions: basic concepts and potential scattering. 12. Electron-atom collisions. 13. Atom-atom collisions. 14. Some applications of atomic physics.

Abstract: In a thermodynamic treatment electromagnetic radiation of any kind is described. The difference between thermal and non-thermal radiation is accounted for by introducing the chemical potential of photons. Instead of an effective temperature all kinds of radiation have the real temperature of the emitting material. As a result Planck's law for thermal radiation is extended to radiation of any kind. The concept of the chemical potential of radiation is discussed in detail in conjunction with light-emitting diodes, two-level systems, and lasers. It allows the calculation of absorption coefficients, of emission spectra of luminescent materials, and of radiative recombination lifetimes of electrons and holes in semiconductors. Theoretical emission spectra are compared with experimental data on GaAs light-emitting diodes and excellent agreement is obtained.

Abstract: The development of pair photon cascades initiated by high energy electrons above a pulsar polar cap is simulated numerically. The calculation uses the energy of the primary electron, the magnetic field strength, and the period of rotation as parameters and follows the curvature radiation emitted by the primary, the conversion of this radiation e(+) - e(-) pairs in the intense fields, and the quantized synchrotron radiation by the secondary pairs. A recursive technique allows the tracing of an indefinite number of generations using a Monte Carlo method. Gamma ray and pair spectra are calculated for cascades in different parts of the polar cap and with different acceleration models. It is found that synchrotron radiation from secondary pairs makes an important contribution to the gamma ray spectrum above 25 MeV, and that the final gamma ray and pair spectra are insensitive to the height of the accelerating region, as long as the acceleration of the primary electrons is not limited by radiation reaction.

Abstract: It is pointed out that, although squeezing and sub-Poissonian photon statistics need not go together, in the sense that an electromagnetic field may exhibit one but not the other, the method that is normally used to detect a squeezed state automatically generates sub-Poissonian photon statistics. However, when these considerations are applied to the fluorescence from a coherently driven atom, which exhibits both squeezing and sub-Poisson fluctuations, one finds that the statistics of the emitted photons show even larger departures from classical field theory than the squeezing.

Abstract: This chapter reviews the electrodynamics of hadrons. Hadrons take part in strong interactions. Hadrons include protons and neutrons with spin 1/2, pions with spin 0, and other particles. Atomic nuclei, which consist of protons and neutrons, are also hadrons. It is impossible to set up equations that determine the electromagnetic interactions of hadrons without taking account of the powerful strong interactions. The hadron current is a phenomenological quantity whose structure is determined by the general kinematic requirements, independent of any assumption about the dynamics of the interactions. If the charged hadron has spin 1/2, the calculations are unchanged; only the specific form of the vertices and propagators is altered. In the limit of low frequencies, the cross section for the scattering of a photon by any charged particle at rest tends to its classical value given by Thomson's formula.

Abstract: This chapter describes asymptotic formulae of quantum electrodynamics. The asymptotic constancy of the total cross-section is a characteristic property of scattering processes whose diagrams can be cut across internal photon lines. It occurs even when more than two particles are present in the final state of the reaction. The double-logarithmic corrections occur in cases of two kinds. One kind includes scattering through a fixed finite angle. The cross-sections decrease in the asymptotic high-energy range. In such cases, the double-logarithmic corrections are associated with the infrared divergence. These cases include elastic scattering of electrons in an external Coulomb field. The other class of cases includes reaction cross-sections, which decrease with increasing energy for a given square of the momentum transfer, that is, for scattering angles, which asymptotically approach zero or π.

Abstract: The effects of scatter and attenuation on single photon emission computed tomography (SPECT) images can be analyzed with the aid of sophisticated Monte Carlo simulation. Correction procedures can be evaluated by comparing corrected images with images absent of scatter and attenuation. The simulation enables control of components which govern the emission and transport of radiation through the source and attenuating medium. The basic calculation involves sampling the probability density functions (pdf) which govern the photon transport process. First, the origin of a photon is selected by sampling. Variance reduction is applied so that a detection is "forced" and weighted by the probability of an initial direction within the acceptance angle of the collimator multiplied by the probability that the photon is not attenuated. Second, the photon history is continued by sampling for a direction. The photon is forced to interact within the attenuating medium and an appropriate weight is calculated. Variance reduction is again applied with a weight determined by the product of the probability of interaction within the attenuating medium, the probability of scatter, the probability of scattering into the acceptance angle of the collimator, and the probability that the photon reaches the detector. Finally, a new direction and energy is selected. If the new energy is below the baseline energy, the history is terminated; otherwise, the second step is repeated. Presently, the collimator's geometric efficiency is considered without septal penetration.

Abstract: The acoustic wave generated by sudden thermal stress is used to obtain information non-invasively on the composition and structure of the stressed body. One or more acoustic transducers (1 and 1') are coupled with the surface of the body to intercept the acoustic wave and generate a corresponding electrical signal. The sudden thermal stress is induced by a pulse of radiation which deposits energy causing a rapid, but very small, rise of temperature. The radiation may be ionizing radiation, such as high energy electrons, photons (X-rays), neutrons, or other charged particles. The radiation may also be non-ionizing radiation, such as RF(2) and microwave electromagnetic radiation (3) and ultrasonic radiation (4). The electrical signal from the acoustic transducer (1) is amplified (5) and supplied to a digitizer (6), which provides a continuous stream of digital words corresponding to samples of the amplified signal. Because in most situations of practical interest the S/N ratio of a single pulse is much less than unity, it is necessary to signal-average the signals from many successive pulses. This is accomplished with a minicomputer or data processor ( 8) suitably interfaced (7) with the digitizer. The resulting data can then be suitably displayed as an image on a CRT display (9) or plotted or numerically printed out.

Abstract: It is proposed to remove the difficulty of nonitegrability of length in the Weyl geometry by modifying the law of parallel displacement and using “standard” vectors. The field equations are derived from a variational principle slightly different from that of Dirac and involving a parameter σ. For σ=0 one has the electromagnetic field. For σ<0 there is a vector meson field. This could be the electromagnetic field with finite-mass photons, or it could be a meson field providing the “missing mass” of the universe. In cosmological models the two natural gauges are the Einstein gauge and the cosmic gauge. With the latter the universe has a fixed size, but the sizes of small systems decrease with time and their masses and energies increase, thus producing the Hubble effect. The field of a particle in this gauge is investigated, and it leads to an interesting solution of the Einstein equations that raises a question about the Schwarzschild solution.

Abstract: Three-photon resonance enhancement of third-harmonic generation and multiphoton ionization is treated for a slab geometry configuration. Striking pressure effects which become important at concentrations $n\ensuremath{\gtrsim}{10}^{12}$ ${/\mathrm{c}\mathrm{m}}^{3}$ for narrow-bandwidth short-pulse lasers are predicted for both the third-harmonic signal and the multiphoton ionization. For example, part of the third-harmonic signal exists the slab simultaneously with the laser pulse while another part is time delayed for small detunings from resonance. At intermediate detuning from the three-photon resonance the two parts can interfere. Multiphoton ionization yields near three-photon resonance are strongly suppressed under certain conditions, and peaks may occur for proper detunings on both sides of the three-photon resonance. A detailed experimental verification is suggested for Xe.

Abstract: On the basis of diffusion approach for normal modes, solutions of the radiative transfer problem are obtained and analysed for an optically thick tenuous plasma with a strong magnetic field. The case is considered when the scattering processes without change of photon frequency ω are dominant. The radiative transfer coefficients as well as spectra, angular dependences and polarization of the outgoing radiation are investigated in detail for a ‘cold’ plasma,kTe≩mc2, |ω−sωB|≫ωkTe/mc2 )1/2|cosϑ|, whereTe is the electron plasma temperature,ωB=eB/mc the electron cyclotron frequency,s=1,2,... the number of cyclotron harmonic and ϑ the angle between the magnetic field and wave vector. The effects of electronpositron vacuum polarization are taken into account and shown to be very significant. Simple analytic solutions are obtained for various limiting cases (small and large vacuum polarization; high, low and close to the cyclotron resonance radiation frequencies; different orientations of the magnetic field, etc). The results obtained are necessary for analysing X-ray and gamma-ray radiation from strongly magnetized neutron stars.

Abstract: A theory of resonantly enhanced degenerate four-wave mixing in two-level systems including the effects of atomic and photon angular momentum is presented in the absence of pump-induced saturation of the transition. It is shown that there exist three distinct quantum-mechanical amplitudes leading to the third-order polarization density. These quantum-mechanical amplitudes are shown to be sensitive to the states of polarization of the incident fields. The quantum-mechanical transport equation in the $m$ representation is used to calculate the output signal in the various regimes of laser detuning, atomic linewidth, and polarization states of the radiation field for collinear interaction.

Abstract: Fundamental experiments on the dual nature of atomic entities (photons, electrons, neutrons, etc.) can be interpreted in terms of “empty” waves not carrying energy and momentum. Similar points of view were advanced in famous papers by Einstein, de Broglie, Bohr, and Born. Recent proposals could lead to experimental tests of this idea, using low intensity photon beams, thanks to modern experimental apparatuses.

Abstract: During the last two decades, various Doppler methods have been successfully used to screen patients with significant cerebral and peripheral vascular disease. In general terms, the principal advantages of Doppler ultrasound techniques in the evaluation of atherosclerotic lesions are that they: 1) are noninvasive, 2) are nontraumatic, 3) are relatively inexpensive, 4) provide anatomical and physiological data, and 5) provide direct and dynamic measurements. Nevertheless, the general limitations of the techniques are of equal importance: 1) the techniques are difficult in some subjects due to obesity and anatomical variations; 2) the technique cannot examine tissues surrounded by air or bone; 3) the techniques require operator skill and a thorough knowledge of human anatomy and cardiovascular dynamics; 4) the techniques have finite spatial resolutions which may compromise the important measurement of vessel diameter, ulceration, and percent stenosis; and 5) the techniques have finite velocity measuring capabilities which may compromise some measurements of highly disturbed blood velocities outside the range of 2-200 cm/sec. As clinical demands for the early diagnosis and quantification of vascular lesions increased, improvements in Doppler ultrasonics and spectra analysis significantly increased the technical and clinical capabilities of existing simple, inexpensive instruments. Presently, both anatomical and physiological images along with quantitative Doppler spectra from superficial and deep-lying vessels can be obtained. Consequently, the ability of Vascular Laboratory, Clinical Research Division; Lovelace Medical Foundation, and the University of New Mexico School of Medicine, Albuquerque, New Mexico 87108 Manuscript received at IEEE April 30, 1982. new expensive imaging equipment to quantitate atherosclerotic lesions using spectral analysis techniques compares favorably with the interpretational precision of standard invasive or intravenous digital angiography. New data suggest that unique hemodynamic information which reflects the effects of cardiac output and vascular input impedance on the hemodynamic consequences of an anatomical lesion can also be obtained. This paper will 1) briefly discuss the general considerations of Doppler ultrasonics; 2) critique the specific characteristics and utility of standard clinical Doppler units; and 3) discuss the ability of new, multipurpose equipment to quantitate (both anatomically and physiologically) atherosclerotic lesions throughout the cardiovascular system.

Abstract: The 15-MV photon beam of a linear accelerator (Siemens Mevatron 20) was studied for electron and scattered photon contamination. The surface dose, attributable almost entirely to contamination electrons, has a Gaussian lateral distribution, a linear dependence on field width for square fields, and an inverse square dependence on distance from the bottom of the fixed head assembly. This geometrical dependence is consistent with the proposal that the field flattening filter is the main source of electron contamination when accessories are absent. A tissue-maximum-ratio curve in the build-up region for the electron and photon contamination was produced utilizing the linearity of dose with respect to field width. The derived contamination curve inside was similar to the measured build-up curve outside the field. The primary photon component, obtained by subtracting the contaminant contribution, showed no dependence on field size, source-to-probe distance, or presence of accessories.

Abstract: A gamma radiation camera and a method are disclosed for creating an image of the radiation density of a source of photons. The camera comprises a detecting device made with solid-state material capable of generating electron-hole pairs as a result of collisions between photons and such material. The camera further includes an identifying device which identifies an ordered pair of said collisions in which both collisions result from a common photon. The camera further includes apparatus for determining an image of said source of common photon from the locations of the collisions of, and the number of electron-hole pairs generated by said ordered pair of collisions. The apparatus for determining an image determines a collision line between two collisions of an ordered pair, and determines the angle of Compton scattering relative to the collision line which occurs at a first of the collisions of such a selected pair. In a preferred embodiment the gamma camera includes a parallel plate collimator placed between the detecting device and the position at which the source of photons is to be located. In such a preferred embodiment, the gamma camera further includes a second line determining device for determining a second line parallel with the collimation plane which forms the determined Compton scattering angle with the collision line at the location of the first collision of the selected pair.

Abstract: Emission of characteristic electromagnetic radiation in the infrared, visible, or UV from excited particles, typically ions, molecules, or neutral atoms, desorbed from solid surfaces by an incident beam of low-momentum probe radiation has been observed. Disclosed is a method for characterizing solid surfaces based on the observed effect, with low-momentum probe radiation consisting of electrons or photons. Further disclosed is a method for controlling manufacturing processes that is also based on the observed effect. The latter method can, for instance, be advantageously applied in integrated circuit-, integrated optics-, and magnetic bubble device manufacture. Specific examples of applications of the method are registering of masks, control of a direct-writing processing beam, end-point detection in etching, and control of a processing beam for laser- or electron-beam annealing or ion implantation.

Abstract: The exact steady-state solution for the reduced atomic density operator for a model system of N identical two-level atoms confined to a single site (the Dicke model) and driven by a totally incoherent broad-band (chaotic) field is derived through the equivalent Fokker-Planck equation of the system. Steady-state values of the atomic observables, higher moments and atomic fluctuations are calculated for an arbitrary N and an arbitrary field strength. It is shown that when the chaotic field is a thermal (black-body) field the atomic system is driven into a steady relative occupation number that obeys the Boltzmann distribution law only for N=1. (The same result for N>1 atoms can be reached only if the cooperative interactions between the atoms are ignored.) In the thermodynamic limit N to infinity there is no critical behaviour in contrast to the resonant coherently driven case. It is also shown that semiclassical (direct) factorisation of the equations of motion does not lead to the correct results for the N to infinity limit of the exact quantum case. Within the exact theory numerical results for finite N (