Electron paramagnetic resonance and photochromism of N3V0\mathrm{N}_{3}\mathrm{V}^{0} in diamond

The defect in diamond formed by a vacancy surrounded by three nearest-neighbor nitrogen atoms and one carbon atom, $\mathrm{N}_{3}\mathrm{V}$, is found in $\approx98\%$ of natural diamonds. Despite $\mathrm{N}_{3}\mathrm{V}^{0}$ being the earliest electron paramagnetic resonance spectrum observed in diamond, to date no satisfactory simulation of the spectrum for an arbitrary magnetic field direction has been produced due to its complexity. In this work, $\mathrm{N}_{3}\mathrm{V}^{0}$ is identified in $^{15}\mathrm{N}$-doped synthetic diamond following irradiation and annealing. The $\mathrm{^{15}N}_{3}\mathrm{V}^{0}$ spin Hamiltonian parameters are revised and used to refine the parameters for $\mathrm{^{14}N}_{3}\mathrm{V}^{0}$, enabling the latter to be accurately simulated and fitted for an arbitrary magnetic field direction. Study of $\mathrm{^{15}N}_{3}\mathrm{V}^{0}$ under excitation with green light indicates charge transfer between $\mathrm{N}_{3}\mathrm{V}$ and $\mathrm{N_s}$. It is argued that this charge transfer is facilitated by direct ionization of $\mathrm{N}_{3}\mathrm{V}^{-}$, an as-yet unobserved charge state of $\mathrm{N}_{3}\mathrm{V}$

Surveying the solar system by measuring angles and times: from the solar density to the gravitational constant

A surprisingly large amount of information on our solar system can be gained from simple measurements of the apparent angular diameters of the sun and the moon. This information includes the average density of the sun, the distance between earth and moon, the radius of the moon, and the gravitational constant. In this note it is described how these and other quantities can be obtained by simple earthbound measurements of angles and times only, without using any explicit information on distances between celestial bodies. The pedagogical and historical aspects of these results are also discussed briefly.Comment: 12 pges, one figur

Generalized Mean Field Approach to a Resonant Bose-Fermi Mixture

We formulate a generalized mean-field theory of a mixture of fermionic and bosonic atoms, in which the fermion-boson interaction can be controlled by a Feshbach resonance. The theory correctly accounts for molecular binding energies of the molecules in the two-body limit, in contrast to the most straightforward mean-field theory. Using this theory, we discuss the equilibrium properties of fermionic molecules created from atom pairs in the gas. We also address the formation of molecules when the magnetic field is ramped across the resonance, and present a simple Landau-Zener result for this process.Comment: 35 page

Fit Into College II: Physical Activity and Nutrition Behavior Effectiveness and Programming Recommendations

Purpose: To determine whether residency (living on campus versus off campus) was related to the effects of Fit into College on students’ health behaviors, and to understand interns’ perceptions of their roles in mentoring their trainees. Design: Pre-experimental, one-group, pretest-posttest design and a posttest focus group interview. Setting: University-offered health and internship courses. Subjects: Twenty-four students (trainees) participated in the intervention, nine of whom lived on campus. Five student-interns served as their mentors. Intervention: Fit into College was a 14-week intervention in which trainees teamed up with an intern to improve and/or maintain healthy nutrition and physical activity behaviors. Measures: Trainees’ nutrition and physical activity behaviors and perceptions were quantitatively assessed through surveys at preintervention and postintervention. Interns’ mentoring perceptions were qualitatively assessed through a focus group interview after the intervention. Analysis: Two-factor repeated measure ANOVAs and qualitative theme identification. Results: Regardless of their residency location, the trainees’ perceptions of the health benefits of eating fruits and vegetables improved during the intervention. However, for trainees living on campus, the intervention was not effective in increasing the number of fruits and vegetables consumed or the planning for food preparation. The interns perceived that they did not have adequate access to healthy foods, the knowledge or skills to prepare healthy foods, or the competency to teach food preparation strategies to their trainees. For trainees living on campus, the intervention was more effective in decreasing perceived exercise barriers than trainees living off campus. Conclusion: Future iterations of Fit into College may focus on 1) improving college students’ planning and preparation of healthy foods, 2) segmenting trainees into more homogeneous groups for the interns to tailor their areas of expertise (campus vs. off-campus and/or freshman vs. upperclass students), and 3) collaborating with university-partners to improve environmental conditions to promote physical activity and healthy nutrition

Bar imprints on the inner gas kinematics of M33

We present measurements of the stellar and gaseous velocities in the central 5' of the Local Group spiral M33. The data were obtained with the ARC 3.5m telescope. Blue and red spectra with resolutions from 2 to 4\AA covering the principal gaseous emission and stellar absorption lines were obtained along the major and minor axes and six other position angles. The observed radial velocities of the ionized gas along the photometric major axis of M33 remain flat at ~22 km s^{-1} all the way into the center, while the stellar velocities show a gradual rise from zero to 22 km s^{-1} over that same region. The central star cluster is at or very close to the dynamical center, with a velocity that is in accordance with M33's systemic velocity to within our uncertainties. Velocities on the minor axis are non-zero out to about 1' from the center in both the stars and gas. Together with the major axis velocities, they point at significant deviations from circular rotation. The most likely explanation for the bulk of the velocity patterns are streaming motions along a weak inner bar with a PA close to that of the minor axis, as suggested by previously published IR photometric images. The presence of bar imprints in M33 implies that all major Local Group galaxies are barred. The non-circular motions over the inner 200 pc make it difficult to constrain the shape of M33's inner dark matter halo profile. If the non-circular motions we find in this nearby Sc galaxy are present in other more distant late-type galaxies, they might be difficult to recognize.Comment: 20 pages, 12 figures, ApJ in pres

Determining a quantum state by means of a single apparatus

The unknown state \hrho of a quantum system S is determined by letting it interact with an auxiliary system A, the initial state of which is known. A one-to-one mapping can thus be realized between the density matrix \hrho and the probabilities of occurrence of the eigenvalues of a single and factorized observable of S+A, so that \hrho can be determined by repeated measurements using a single apparatus. If S and A are spins, it suffices to measure simultaneously their $z$-components after a controlled interaction. The most robust setups are determined in this case, for an initially pure or a completely disordered state of A. They involve an Ising or anisotropic Heisenberg coupling and an external field.Comment: 5 pages revte

Levinson's theorem for the Schr\"{o}dinger equation in two dimensions

Levinson's theorem for the Schr\"{o}dinger equation with a cylindrically symmetric potential in two dimensions is re-established by the Sturm-Liouville theorem. The critical case, where the Schr\"{o}dinger equation has a finite zero-energy solution, is analyzed in detail. It is shown that, in comparison with Levinson's theorem in non-critical case, the half bound state for $P$ wave, in which the wave function for the zero-energy solution does not decay fast enough at infinity to be square integrable, will cause the phase shift of $P$ wave at zero energy to increase an additional $\pi$.Comment: Latex 11 pages, no figure and accepted by P.R.A (in August); Email: [email protected], [email protected]

John O. Newton Correspondence

Entries include brief biographical information, a typed biographical letter, and a handwritten letter of correspondence on plain paper