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Recent years have seen the accumulation of a considerable amount of new information, both experimental and theoretical, pertaining to the location and character of the excited states in the light nuclei. We have attempted in the following sections to summarize the pertinent facts appearing in the literature and to present this material in a systematic way. To a large extend the organization of the present article follows the pattern of the two previous papers on this subject.(1,2) The present article contains a summary of the most important information appearing in the earlier papers and is intended to supersede them entirely.

Recent years have seen the accumulation of a considerable amount of new information, both experimental and theoretical, pertaining to the location and character of the excited states in the light nuclei. We have attempted in the following sections to summarize the pertinent facts appearing in the literature and to present this material in a systematic way. To a large extend the organization of the present article follows the pattern of the two previous papers on this subject.(1,2) The present article contains a summary of the most important information appearing in the earlier papers and is intended to supersede them entirely.

A theory, which exhibits the characteristic features of scatterings initiated by two coherent beams, is discussed in the present paper. We show that the imaginary part of the scattering amplitude is an experimentally measurable quantity. To know the imaginary part of the amplitude is quite important for certain aspects of quantum mechanics, for example, the dispersion relation for a fixed momentum transfer. This relation has not yet been experimentally verified.

An attempt is made in the present paper to give a physical description of the process in which a gamma quantum is resonantly scattered or absorbed by nuclei bound in a crystal structure. The discussion includes a description of the time development of these processes as well as a critical study of the limits imposed upon such a description by the laws of quantum mechanics.(1)

Series spectra of three-valence-electron atoms of P, S and Cl.—By the methods of the preceding paper, 21 lines of PIII have been identified, 20 lines of SIV and 10 lines of ClV, including a pp′ group for each; also 10 term values of PIII have been determined and 10 term values of SIV, including the x level. Screening constants for one, two, and three valence electron systems are collected in a table for Na to Cl. The values increase regularly with the number of valence electrons and decrease with the atomic number, the difference decreasing as the atomic number increases.

There is a pressure drop associated with an increase in the flow rate of a moving fluid. The venturi meter and the aspirator are familiar devices which derive from this phenomenon. This paper concerns itself with the detection of an analogous effect in the electron gas in a metal.

An attempt is made in the present paper to give a physical description of the process in which a gamma quantum is resonantly scattered or absorbed by nuclei bound in a crystal structure. The discussion includes a description of the time development of these processes as well as a critical study of the limits imposed upon such a description by the laws of quantum mechanics.(1)

The invited speakers have done an excellent job of describing the various topics within the field of weak interactions. The contributed papers have presented many fascinating results. Furthermore, what is rare these days at a physics conference, there has been plenty of discussion, which has brought out, I think, every point that was overlooked in the speeches. Evidently, there is no need for a summary. A few words about what appear to me to be the principal questions that we would like to have answered in the future are given in the following.

In most recoilless gamma-ray resonance experiments the magnetic-dipole and electric-quadrupole hyperfine interaction do not cause any shift of the center of gravity of the velocity spectrum. This is usually related to the fact that the trace of the hyperfine-interaction Hamiltonian is zero. Nevertheless a large shift can be caused under proper conditions by a magnetic hyperfine interaction in second order, the so-called "pseudoquadrupole" interaction.(1) This paper reports the first observation of the pseudoquadrupole shift of gamma lines.(2)

Calculations of many physical processes according to the SU(12) theories(1) can be facilitated by the use of appropriate subgroups of SU(12). Direct calculations are difficult because of the complexity of the group and the present lack of available Clebsch-Gordan coefficients. Tables of SU(6) Clebsch-Gordan coefficients do exist,(2) however, and have been used for calculations of non-relativistic processes. In this paper we present SU(6) subgroups which differ from the conventional SU(6) by the replacement of ordinary spin by different SU(2) subgroups of SU(12).

The invited speakers have done an excellent job of describing the various topics within the field of weak interactions. The contributed papers have presented many fascinating results. Furthermore, what is rare these days at a physics conference, there has been plenty of discussion, which has brought out, I think, every point that was overlooked in the speeches. Evidently, there is no need for a summary. A few words about what appear to me to be the principal questions that we would like to have answered in the future are given in the following.

An attempt is made in the present paper to give a physical description of the process in which a gamma quantum is resonantly scattered or absorbed by nuclei bound in a crystal structure. The discussion includes a description of the time development of these processes as well as a critical study of the limits imposed upon such a description by the laws of quantum mechanics.(1)

There is a pressure drop associated with an increase in the flow rate of a moving fluid. The venturi meter and the aspirator are familiar devices which derive from this phenomenon. This paper concerns itself with the detection of an analogous effect in the electron gas in a metal.

In most recoilless gamma-ray resonance experiments the magnetic-dipole and electric-quadrupole hyperfine interaction do not cause any shift of the center of gravity of the velocity spectrum. This is usually related to the fact that the trace of the hyperfine-interaction Hamiltonian is zero. Nevertheless a large shift can be caused under proper conditions by a magnetic hyperfine interaction in second order, the so-called "pseudoquadrupole" interaction.(1) This paper reports the first observation of the pseudoquadrupole shift of gamma lines.(2)

Calculations of many physical processes according to the SU(12) theories(1) can be facilitated by the use of appropriate subgroups of SU(12). Direct calculations are difficult because of the complexity of the group and the present lack of available Clebsch-Gordan coefficients. Tables of SU(6) Clebsch-Gordan coefficients do exist,(2) however, and have been used for calculations of non-relativistic processes. In this paper we present SU(6) subgroups which differ from the conventional SU(6) by the replacement of ordinary spin by different SU(2) subgroups of SU(12).

Series spectra of three-valence-electron atoms of P, S and Cl.—By the methods of the preceding paper, 21 lines of PIII have been identified, 20 lines of SIV and 10 lines of ClV, including a pp′ group for each; also 10 term values of PIII have been determined and 10 term values of SIV, including the x level. Screening constants for one, two, and three valence electron systems are collected in a table for Na to Cl. The values increase regularly with the number of valence electrons and decrease with the atomic number, the difference decreasing as the atomic number increases.

This paper develops a single-collision theory of the emission of electrons from a metal surface subjected to high-energy ion bombardment, which gives reasonable agreement with the data of Carlston, Magnuson, Mahadevan, and Harrison, in the 1to 10-keV energy range. The model is based upon a Thomas-Fermi-Firsov energy-transfer calculation which has been modified to include an explicit dependence upon lattice orienta­tion. Orientation effects appear naturally, and orientation-dependent cross sections are not required, but the distribution of possible impact parameters for a particular crystal orientation is of central importance. The theory has been used to determine semiempirical interaction potentials between the moving particle and a lattice atom. These potentials are more similar to Abrahamson's atom-atom potentials than to the Gibson potentials used in radiation-damage studies.