Ground State Occupation Research Articles

Hyperfine structure in highly ionized 13C atoms and the magnetic moment of the state at 3.85 MeV

The time dependence of the angular correlation due to the hyperfine interaction of the 3.85 MeV 52+ level of 13C (τm = 12.4 ± 0.8 ps) in carbon ions of high-charge states has been investigated. The highest frequency seen was attributed to the hyperfine interaction of a single K-electron with the nuclear state, and from this a value for the nuclear ifg-factor of the 3.85 MeV level ¦g¦ = 0.59 ± 0.05 can be inferred. The results also provide information on the atomic ground-state occupancies in the 4+ and 5+ carbon ions, after emergence from a target foil at a velocity v/c ≈ 0.04.

Hyperfine interactions of excited nuclei in highly ionized atoms

The hyperfine interaction of excited nuclear levels with deeply ionized atoms is discussed. A measurement is reported for 18O(2+) at 1.98 MeV, interacting with 7+ ions in the 1s state. Limits for the g factor of this level are reported as: 0.2< mod g mod <0.36. The excitation pattern of highly stripped ions is considered and it is concluded that such ions are formed in two distinct patterns, one characterized by predominant ground state occupation and the other by prolific excitation. The feature which determines the pattern is the degree of isolation of the ground state of the ions.

Hyperfine Interactions of the First Excited2+State ofO18in7+and6+Ions

Perturbed angular correlations were measured between 1.98-MeV $\ensuremath{\gamma}$ rays de-exciting the 3.3-psec ${2}^{+}$ state of $^{18}\mathrm{O}$ and the $^{18}\mathrm{O}^{*}$ particles following the reaction $^{12}\mathrm{C}$($^{18}\mathrm{O}$, $^{18}\mathrm{O}^{*}$)$^{12}\mathrm{C}$ at 33 MeV. A magnetic spectrometer was used to resolve the $^{18}\mathrm{O}^{*}$ ions into the component ${8}^{+}$, ${7}^{+}$, and ${6}^{+}$ charge states, and the correlations were determined separately for each. The measurements yield information on hyperfine interactions in the ${7}^{+}$ and ${6}^{+}$ charge states. Limits are obtained on the ionic ground-state occupancies and on the value of the nuclear $g$ factor.

Fluctuations and superfluidity in finite systems

Considerations of the density fluctuations and the ground-state occupancy of a finite Bose-Einstein system lead to a workable criterion for the onset of superfluidity. The criterion is applied to thin films and narrow channels.

Distribution methods for nuclear energies, level densities, and excitation strengths

The centroid energies and widths for configurations, both with and without a specification of isospin, are given in compact forms in which the various terms have a clear physical significance. The forms are derived by use of elementary unitary-group methods which lead to an orthogonal symmetry decomposition of the Hamiltonian, in which Hartree-Fock-like terms representing the induced single-particle energies, and other related quantities, enter in a natural way. Appropriate measures for the various terms are given and discussed. The same method is applicable to the more complicated operators encountered when dealing with excitation strengths of various kinds. Some applications are given to determining ground-state energies, orbit occupancies, and low-lying spectra for complicated systems, and comparisons made with shell-model calculations and with experiment. An account, with some elementary applications, is given of a distribution theory of level densities which takes into consideration the shell-model structures and residual interactions; to specify the densities for fixed angular momentum, the configuration distributions are used to derive the energy variation of the J z 2 and J z 4 averages, the first of these fixing the “spin cut-off factor” σ(J), and the second verifying the accuracy of the Gaussian form commonly used. Finally, an introductory account is given of the distributions of single-particle transfer and electromagnetic-transition strengths in large shell-model spaces.

Fluctuations in the population of the ground state of Bose Systems

Formulas are given which show how the fluctuations of the ground-state occupation number in a Bose System are strongly suppressed at low temperatures.

Theory of Nuclear Level Density for Periodic Independent-Particle Energy-Level Schemes

Accurate and perspicuous formulas are derived for the density of states of a degenerate system of any number of types of fermions moving in arbitrary periodic single-particle energy-level schemes. The results are of the standard form with the modification that the excitation energy is to be replaced by an "effective energy." The effective energy contains an additive correction which depends explicitly on the structure and ground-state occupation of the periodic level sequences. The spin-dependent level-density formula for two kinds of particles should be useful in the correlation of observed nuclear level densities with shell-model level sequences. The present work generalizes, unifies, and simplifies earlier treatments of related problems.

A study of the 26Mg( 3He, d) 27Al reaction

Angular distributions of deuterons from the 26Mg( 3He, d) 27Al reaction have been analysed with DWBA calculations to extract spectroscopic factors for most states in 27Al up to 4.58 MeV excitation. Ground state occupation numbers for d 5 2 , s 1 2 and d 3 2 orbits in the 26Mg ground state, and the single-particle centroids in 27Al are obtained. The results are in reasonable agreement with the excited core model of the low-lying states of 27Al. The negative parity state at 4.05 MeV in 27Al is shown to be a 1p hole state rather than a 2p particle state. Finally, a previous estimate of the excitation of d 3 2 particles in the ground state of 28Si is shown to be questionable.

Ground-State Occupancy of an Ideal Bose-Einstein Gas Confined to a Finite Volume

The number of particles in the ground state has been computed as a function of temperature for an ideal Bose-Einstein gas confined to a box of finite volume by evaluating the discrete sum over states on a computer. Large deviations from London's bulk-gas result are found when the length of the box is much greater than its width for the range of dimensions investigated here. It is shown that the deviations occur because in this limit the system tends to behave like a one-dimensional system.

Collision interference effects in a bose-einstein gas

Synopsis Possible interference effects between successive binary collisions in a Bose-Einstein assembly of interacting particles are examined by carrying perturbation treatment to fourth order. It is concluded that the Boltzmann equation is insufficient to describe the rate of change of the ground state occupation number in the condensed state.