Abstract: An angular analog of the Doppler effect arising from the quantum of angular momentum carried by circularly polarized photons is presented and developed. Applications to rotational Raman scattering, fluorescence doublets, controlled frequency shifting of light, rotation-induced optical activity, and the measurement of rotational motion of small particles are discussed.

Abstract: The authors present a theory of electron-photon coincidence experiments with polarised electrons, taking spin-orbit coupling effects during the excitation into account. The influence of the initial polarisation vector on the angular distribution and polarisation of the emitted photons is discussed in detail. As an explicit example the excitation process 1S0 to 3P1 in mercury is considered. Finally, the results are specialised to experiments where the scattered electrons are not observed. Using symmetry arguments and deriving additional selection rules they relate the degree of light polarisation to the initial polarisation. Two experimental results are presented.

Abstract: Using a two-slit neutron interferometer, we have measured the shift of the interference pattern induced by the motion of a quartz rod. The measured shift is found to be in agreement with the quantum mechanical prediction derived from a relativity argument. Some peculiarities of the case of massive particles as compared with the classic Fizeau photon case are discussed.

Abstract: Radiation emission over a wide range (5--5000 A) of wavelengths in a high-density aluminum plasma has been studied theoretically. The atomic model includes explicit treatment of a large number of states and transitions characterizing the line emission from the Al III--Al XIII ions. The state populations are calculated using a set of atomic rate equations describing a plasma in collisional-radiative equilibrium. The ionization state of the plasma is calculated self-consistently with line and continuum radiation transport using a one-dimensional multicell structure for the plasma. A new radiation transport scheme has been implemented in this model based on probability of escape for both line and continuum photons. The total L- and K-shell radiation emission is described as a function of plasma temperature, density, and source size, and is compared to predictions made from corona and local thermodynamic equilibrium models. It is shown that over a wide range of plasma parameters, neither of these two limiting models accurately describes the plasma emission characteristics. Several line intensity ratios from L-shell lines are studied and shown to be useful diagnostic indicators of the plasma temperature and density. Finally, theoretical spectra are calculated and discussed in the context of their comparability with experimental spectra inmore » order to make contact with real plasma radiation signatures and exploit the predictive capabilities of the model.« less

Abstract: Stemming from the classic work of Planck, classical radiative transfer theory works with pencils of light rays streaming in straight lines in any homogeneous medium. But light is described by Maxwell's equations in classical and quantum electrodynamics, and so we need to find a bundle of rays equivalent to the electromagnetic waves. In this paper we realize such a pencils of light rays. Their properties and the equations obeyed by the ray density function are deduced. We need to generalize radiative transfer theory for this purpose appropriately. For homogeneous statistical wave fields radiative transfer theory obtains rigorously. Particular attention is paid to the polarization properties of light rays. These concepts have some relation with the phase-space picture of quantum mechanics. Also, other general questions including possible further developments are discussed.

Abstract: A formalism is derived that relates the absorbed dose to a medium from photon and electron beams to the photoncalibration factor of an ionization chamber. The formalism is applicable to the photon and electron beam energies that are currently of interest in radiation therapy. It is developed in terms of a cavity‐gas calibration factor, a quantity characteristic of the chamber and independent of the energy of the calibration beam assuming the energy expended per ion pair is energy independent. The cavity−gas calibration factor can be obtained from a chamber calibration performed in terms of exposure,absorbed dose to water,or air kerma. The perturbation corrections due to replacement of the surrounding medium by the chamber wall and cavity are identified as ratios of the photon energy fluence,or the electron fluence, at the position of the chamber center. The unmanageable complexities of a theory that covers an ionization chamber made of several materials are avoided by limiting the development to a chamber made of a single material with the expectation that the inhomogeneities of real chambers can be treated as perturbations. Attention is called to certain theoretical aspects of this dosimetry development that do not appear to have been previously recognized.

Abstract: The angular asymmetry parameter β has been determined for the first four bands in the photoelectron spectrum of CO2 as a function of photon energy: X 2Πg(15–50 eV), A 2Πu(19–28 eV), B 2Σu+(19–28 eV), and C 2Σg+(21–67 eV). Use is made of a monochromatized beam of photons from the Wisconsin Synchrotron Radiation Center. The experimental results are compared with theoretical calculations employing the multiple scattering method and the overall agreement is good. In addition, the theoretical predictions for the effect on β of shape resonances have been verified except that the experimental widths are broader. This broadening has been partially accounted for in recent calculations of Swanson et al. by including the effects of vibrational motion. Finally, sharp changes in β as a function of vibrational level have been noted for the second and fourth electronic bands. Such behavior has been found for a variety of photon energies, and the results are examined against prevailing theory.

Abstract: Relative bremsstrahlung cross sections have been measured for free atoms, with atomic numbers in the range $Z=2$ to $Z=92$, at low incident electron energies of 2.5 and 10 keV. The results agree reasonably with a theoretical calculation of Pratt et al., except at the largest $Z$ number, where differences of up to a factor of 2 at low photon energies are observed.

Abstract: A perturbation theory approach is used to analyze the rovibronic structure of the three‐photon resonant absorption of ammonia. The vibronic selection rules are presented in a convenient pyramid mnemonic in terms of irreducible representations of the rotation group and of the D3h point group. The analysis is presented for each possible situation, namely, all three photons are different, two photons are identical and one different, and all three photons are identical. The experimentally important case of three identical photons implies only two polarizations and two vibronic tensor elements for each symmetry type. With both the B and C′ systems of ammonia one expects a ratio of 5 to 2 in the absorbance for circularly versus linearly polarized light for the N, O, S, and T branches. For the P, Q, and R branches one expects a 21 to 4 ratio of the weight‐1 versus weight‐3 tensor contributions to the C′ system in linearly polarized light (21 to 6 for B). Weight‐1 terms are absent with circularly polarized li...

Abstract: A modified electron-photon coincidence experiment on the excitation of the 31D state of helium is suggested. The idea is to measure the scattered electrons, which have excited the 31D state, in coincidence with 21P to 11S photons resulting from the 31D to 21P to 11S cascade. Due to their large energy the latter can be detected with higher efficiency than the directly emitted 31D to 21P photons. A theory is developed to show that the proposed experiment yields exactly the same information on the 31D excitation as a conventional coincidence experiment between scattered electrons and 31D to 21P photons. Preliminary experiments have been performed, in which the 31D excitation is measured simultaneously with the 31S and 31P excitation. The coincidence signal due to the 31S excitation, with its isotropic radiation field is used to calibrate the 31P and 31D measurements.

Abstract: A model using rate equations which allow for quantum noise is used to make a theoretical analysis of the steady-state lasing regime of a cw dye laser. Equations describing the laser performance are derived in the adiabatic approximation neglecting spatial inhomogeneities in the burnup of the active medium. An investigation is made of the stability of steady-state multimode laser action and it is found that this is weak in certain modes. Calculations are made of correlation functions describing fluctuations in the numbers of photons in the modes and fluctuations in the total intensity. Although the fluctuations in individual modes are large, the integrated intensity fluctuates negligibly. An analysis is made of the influence of quantum intensity fluctuations on the attainment of maximum sensitivity in intracavity laser spectroscopy.

Abstract: Lifetimes of 49 excited states below 1.65 MeV have been measured in 24Mg, 27Al, 48Ti, 58Ni, 59Co, 61,62Ni, 63,65Cu, 64,66,68Zn, 75As, 103Rh, 113,115In, 116,118,120Sn and 121,123Sb by means of nuclear resonance fluorescence experiments. The levels are excited by bremsstrahlung X-ray photons. The self-absorption technique applied to suitable cases provides nuclear absorption cross sections, widths and lifetimes from which the X-ray spectral distributions are also obtained. Scattering experiments are performed for all other cases in order to obtain widths and lifetimes from these X-ray photon curves. The Compton effect in the sample is taken into account.

Abstract: We present results of a detailed analysis of inclusive direct photon production at the (3095). The direct-photon momentum distribution for x>0.4 is presented and compared with the leading-order quantum-chromodynamic prediction. The total production rate is found to be consistent with theoretical expectations, but the observed momentum distribution is considerably softer. Results of an analysis of some inclusive properties of the hadronic system recoiling against the direct photon are presented. The mean charged-particle and Ks multiplicities are presented as functions of the invariant mass of the hadronic system. These data agree well with the corresponding mean multiplicities measured in e+e- annihilations at center-of-mass energies comparable to the invariant mass of the hadronic system. © 1981 The American Physical Society.

Abstract: I. INTRODUCTION If electrons are removed from the inner shells of atoms the vacancies created are filled by electrons from higher energy levels, giving rise to the emission of radiation. For all but the lightest elements this emission is in the X-ray region of the electromagnetic spectrum. The energy of the emitted X-ray is characteristic of the element emitting the radiation and hence its observation forms a method of identification. The initial inner-shell ionization of the atom can be initiated by bombarding the sample under investigation with photons, electrons, or heavier charged particles, such as alpha particles or protons, giving rise to a variety of microanalytical techniques; X-ray fluorescence analysis, electron microprobe analysis, alpha particle and proton-induced X-ray emission analysis.

Abstract: A static periodic magnetic field (wiggler) together with a radiation field, can induce a beat wave in the presence of an injected electron beam. This beat wave, if properly phased, can trap and continuously energize the electron beam. To optimize the transfer of energy from the photons to electrons, both the wiggler amplitude and wavelength are spatially increased as a function of acceleration distance. The acceleration process is self-consistently analyzed and includes radiation depletion and space charge effects. Two numerical illustrations are given using different radiation sources.

Abstract: Elastic scattering by nuclei in the range of mass numbers between 64 and 238 has been studied with monochromatic photons in the energy range between 2 and 8 MeV. These photons were provided either by a Ti(n,γ) source installed in the tangential through channel of the Grenoble high flux reactor, or by24Na and56Co sources produced by deuteron bombardment of Al or Fe at the Gottingen cyclotron. The photoexcitation of 23 nuclear levels has been observed and the decay properties and groundstate widths of the majority of these levels have been determined. For the lead scattering target the coherent elastic differential cross section has been studied in detail. There is evidence that below the photo-neutron threshold the elastic scattering via virtual photoexcitation of the nucleus can be approximated by extrapolating the real part of the Giant Dipole Resonance amplitude along a Lorentzian curve. Coulomb corrections to Delbruck scattering seem to play a small role at 6.5 MeV.

Abstract: Linear and circular polarisation measurements have been carried out for photons from the 63P1-61S0 transition in mercury, which were detected in delayed coincidence with electrons having excited the 63P1 state. These measurements have been used to determine values for the parameters lambda , chi and the spin-orbit phase angles Delta and epsilon for the 61S0 to 63P1 to 61S0 excitation/de-excitation process in mercury.

Abstract: The spatial photon intensity distribution is calculated for geometries pertinent to tapered‐wiggler free‐electron lasers. A large‐radius incident photon field interacts with a small‐radius e‐beam gain medium, and the diffraction of extracted energy from the gain medium to larger radii is analyzed in the limit of small gain. The results are compared with a simple fill‐factor approximation.

Abstract: The quantum theory of the statistical properties and the photocount statistics of intense radiation in Raman scattering are presented making use of the coherent-state techniques. Both the Heisenberg-Langevin and Fokker-Planck equations approaches are developed. The existence of the conditional Glauber-Sudarshan quasi-distribution is also discussed. The time dependences of the photocount distribution and its factorial moments are demonstrated in the case of stimulated scattering and anticorrelation and antibunching of scattered photons are found.