Magnetic Field Effects on the 1083 nm Atomic Line of Helium. Optical Pumping of Helium and Optical Polarisation Measurement in High Magnetic Field

The structure of the excited $2^{3}$S and $2^{3}$P triplet states of $^{3}$He and $^{4}$He in an applied magnetic field B is studied using different approximations of the atomic Hamiltonian. All optical transitions (line positions and intensities) of the 1083 nm $2^{3}$S-$2^{3}$P transition are computed as a function of B. The effect of metastability exchange collisions between atoms in the ground state and in the $2^{3}$S metastable state is studied, and rate equations are derived, for the populations these states in the general case of an isotopic mixture in an arbitrary field B. It is shown that the usual spin-temperature description remains valid. A simple optical pumping model based on these rate equations is used to study the B-dependence of the population couplings which result from the exchange collisions. Simple spectroscopy measurements are performed using a single-frequency laser diode on the 1083 nm transition. The accuracy of frequency scans and of measurements of transition intensities is studied. Systematic experimental verifications are made for B=0 to 1.5 T. Optical pumping effects resulting from hyperfine decoupling in high field are observed to be in good agreement with the predictions of the simple model. Based on adequately chosen absorption measurements at 1083 nm, a general optical method to measure the nuclear polarisation of the atoms in the ground state in an arbitrary field is described. It is demonstrated at $B\sim$0.1 T, a field for which the usual optical methods could not operate.Comment: 33 pages, 31 figures, 17 tables, 61 references. Revised version (typos corrected, figure 11 replaced by the proper one) Accepted for publication in EPJ

"Quantum Interference with Slits" Revisited

Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his calculation as if no approximations are employed. We show that he implicitly makes the same approximations found in classical treatments of interference and that no new physics has been introduced. At the same time, some of the quantum mechanical arguments Marcella gives are, at best, misleading.Comment: 11 pages, 3 figure

Differential Selection in Juniper Populations from the Baum Limestone and Trinity Sand of Southern Oklahoma

Two markedly different geologic formations, the Baum limestone and Trinity sand and an area of intermixed talus were compared for several physical attributes and these correlated with the structure of the plant communities occupying them and with the variability of a conspicuous constituent for each of the three habitats. (1) Juniperus Ashei occupies the Baum Limestone in nearly pure stands, but with wide spacing, while the general cover consists of Bouteloua hirsula and Andropogon scoparius. The limestone has a high carbonate content, high hygroscopic coefficient, low soil moisture. (2) Juniperus virginiana occupies the Trinity sand on cleared, reverted land normally supporting a post-oak, black-jack oak forest. The junipers are widely spaced with oak forest in various stages of regeneration. Woody cover as well as ground cover is greater on the Trinity than on the Baum. The Trinity has low carbonate, low hygroscopic coefficient, high soil moisture. (3) The juniper population on the mixed talus sites are hybrid but closer to Juniperus Ashei. The various factors measured are intermediate between the other two habitats. (4) The data suggest that in southern Oklahoma J. Ashei develops plentifully in areas where the moisture content is low enough to limit J. virginiana, but as the habitats of the two species intergrade hybridization occurs, i.e., currently as well as historically, with only those hybrids surviving which are adapted to the intermediate habitats. (5) These mixed habitats are rich sources for continued hybridization and introgression until succession closes both the mixed habitats and the Trinity sand to junipers

Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emission

We report the first results from our long-term observational survey aimed at discovering late-time interaction between the ejecta of hydrogen-poor Type I supernovae and the hydrogen-rich envelope expelled from the progenitor star several decades/centuries before explosion. The expelled envelope, moving with a velocity of ~10 -- 100 km s$^{-1}$, is expected to be caught up by the fast-moving SN ejecta several years/decades after explosion depending on the history of the mass-loss process acting in the progenitor star prior to explosion. The collision between the SN ejecta and the circumstellar envelope results in net emission in the Balmer-lines, especially in H-alpha. We look for signs of late-time H-alpha emission in older Type Ia/Ibc/IIb SNe having hydrogen-poor ejecta, via narrow-band imaging. Continuum-subtracted H-alpha emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb and 3 SN Ia events. Thirty-eight SN sites were observed on at least two epochs, from which three objects (SN 1985F, SN 2005kl, SN 2012fh) showed significant temporal variation in the strength of their H-alpha emission in our DIAFI data. This suggests that the variable emission is probably not due to nearby H II regions unassociated with the SN, and hence is an important additional hint that ejecta-CSM interaction may take place in these systems. Moreover, we successfully detected the late-time H-alpha emission from the Type Ib SN 2014C, which was recently discovered as a strongly interacting SN in various (radio, infrared, optical and X-ray) bands.Comment: 8 pages, 7 figures, accepted in Ap

Cross Section and Angular Distributions of the (d, p) and (d, n) Reactions in C12 from 1.8 to 6.1 Mev

The reaction C12(d, p)C13 has been studied from a deuteron bombarding energy of 1.8 to 6.1 Mev. Resonances were found at 2.47, 2.67, 2.99, 3.39, 4.00, 4.6, 4.8, 5.34, and 5.64 Mev. Angular distributions of protons leaving C13 in the ground state show a pronounced Butler peak at 25° over the entire deuteron energy range. The angular distributions can be explained by assuming small amplitudes for compound nucleus formation interfering with large stripping amplitudes. Angular distributions of the lower energy group of protons leaving C13 excited to 3.09 Mev show a pronounced Butler peak at 0° and an even smaller contribution of compound nucleus formation. The reaction C12(d, n)N13 was also studied, and showed similar resonances and angular distributions. An analysis is made of the phase difference between the resonant and nonresonant parts of the cross section for the (d, p) reaction near the resonance at 4.00 Mev

Hybridization Between Juniperus Ashei Buchholz and Juniperus Pinchoti Sudworth in Southwestern Texas

This paper presents an analysis of the interactions of two processes, hybridization and differential selection, in the diversification of Juniperus where Juniperus Ashei Buchholz and Juniperus Pinchoti Sudw. occur together. An attempt is made to show man\u27s influence toward accelerating these interactions

The Unusually Luminous Extragalactic Nova SN 2010U

We present observations of the unusual optical transient SN 2010U, including spectra taken 1.03 days to 15.3 days after maximum light that identify it as a fast and luminous Fe II type nova. Our multi-band light curve traces the fast decline (t_2 = 3.5 days) from maximum light (M_V = -10.2 mag), placing SN 2010U in the top 0.5% of the most luminous novae ever observed. We find typical ejecta velocities of approximately 1100 km/s and that SN 2010U shares many spectral and photometric characteristics with two other fast and luminous Fe II type novae, including Nova LMC 1991 and M31N-2007-11d. For the extreme luminosity of this nova, the maximum magnitude vs. rate of decline relationship indicates a massive white dwarf progenitor with a low pre-outburst accretion rate. However, this prediction is in conflict with emerging theories of nova populations, which predict that luminous novae from massive white dwarfs should preferentially exhibit an alternate spectral type (He/N) near maximum light.Comment: 16 pages, 16 figures. Submitted to the Astrophysical Journa