Probing Bose-Einstein Condensation of Excitons with Electromagnetic Radiation

We examine the absorption spectrum of electromagnetic radiation from excitons, where an exciton in the $1s$ state absorbs a photon and makes a transition to the $2p$ state. We demonstrate that the absorption spectrum depends strongly on the quantum degeneracy of the exciton gas, and that it will generally manifest many-body effects. Based on our results we propose that absorption of infrared radiation could resolve recent contradictory experimental results on excitons in Cu$_2$O.Comment: 4 pages, RevTex, 8 ps figures, submitted to PR

Measurements of ion-molecule reactions of He plus, H plus, HeH plus with H sub 2 and D sub 2

A drift tube mass spectrometer apparatus has been used to determine the rate coefficient, energy dependence and product ions of the reaction He(+) +H2. The total rate coefficient at 300 K is 1.1 plus or minus 0.1) 10 to minus 13th power cu cm/sec. The reaction proceeds principally by dissociative charge transfer to produce H(+), with the small remainder going by charge transfer to produce H2(+) and by atom rearrangement to produce HeH(+). The rate coefficient increases slowly with increasing ion mean energy, reaching a value of 2.8 x ten to the minus 13th power cu cm sec at 0.18 eV. The corresponding reaction with deuterium, He(+) + D2, exhibits a value (5 plus or minus 1) x 10 to the minus 14th cu cm/sec at 300K. The reaction rates for conversion of H(+) and HeH(+) to H3(+) on collisions with H2 molecules are found to agree well with results of previous investigations

Mobilities of uranium and mercury ions in helium

The mobilities of mass-identified U(+) and Hg (+) ions in helium were determined in a drift tube-mass spectrometer. For uranium ions, a reduced mobility value is obtained at 305 K and a standard gas density of 2.69 x 10 to the 19th power/cu cm. The mobility of mercury ions is in agreement with two previous determinations. The effect of fast ion injection in drift mobility measurements is discussed, and a technique to circumvent these problems is described. The results are compared with existing theories of ion mobilities

Electron-temperature dependence of dissociative recombination of electrons with CO(+)-(CO)n-series ions

A microwave afterglow mass spectrometer apparatus is used to determine the dependence on electron temperature T sub e of the recombination coefficients alpha sub n of the dimer and trimer ions of the series CO+.(CO) sub n. It is found that alpha sub 1 = (1.3 + or - 0.3)x 0.000001 (T sub e(K)/300) to the -0.34; and alpha sub 2 = (1.9 + or - 0.4)x 0.000001 (T sub e(K)/300) to the -0.33 cu cm/sec. These dependences on T sub e are quite different from those obtained previously for polar-cluster ions of the hydronium and ammonium series but are similar to that for simple diatomic ions

Measurements of recombination of electrons with H3(plus) and H5(plus) ions

The electron-ion recombination coefficients for H3(+) and H5(+) ions were determined by means of a microwave afterglow/mass spectrometer apparatus. Measurements of electron density decays in helium-hydrogen mixtures are correlated with the decay of mass-identified ion currents to the wall of the microwave cavity. At low partial pressures of hydrogen in the mixture, the ion H3(+) dominates the ion composition and the ion wall current tracks the electron density decay curves. From recombination controlled electron density decay curves, the values alpha (H3(+)) = (2.9 + or - 0.3), (2.3 + or - 0.3), and (2.0 + or - 0.2) x 0.0000001 cu cm per sec, are obtained at 205, 300 and 450 K, respectively. At higher partial pressures of hydrogen and low temperatures, where (H5(+)) is the dominant ion, the value alpha (H5(+)) = (3.6 + or - 1.0) x 0.0000001 cu cm per sec is obtained at 205 K. The implications of these results concerning ionization levels in the atmospheres of the outer planets and in the interstellar medium are discussed

Measurements of the O+ plus N2 and O+ plus O2 reaction rates from 300 to 900 K

Rate coefficients for the O(+) + N2 atom transfer and O(+) + O2 charge transfer reactions are determined at thermal energies between 300 K and 900 K difference in a heated drift tube mass spectrometer apparatus. At 300 K the values K(O(+) + N2) = (1.2 plus or minus 0.1) x 10 to the negative 12 power cubic cm/sec and k(O(+) + O2) = (2.1 plus or minus 0.2) x 10 to the negative 11 power cubic cm/sec were obtained, with a 50% difference decrease in the reaction rates upon heating to 700 K. These results are in good agreement with heated flowing afterglow results, but the O(+) + O2 thermal rate coefficients are systematically lower than equivalent Maxwellian rates inferred by conversion of nonthermal drift tube and flow drift data

Reactions of Na/plus/, K/plus/, and Ba/plus/ ions with O2, NO, and H2O molecules

Investigating ion molecule reactions of sodium, potassium, and barium ions with oxygen, nitric oxide, and water in drift tube mass spectromete

Building a Bench: A Close Look at State Appellate Courts Constructed by the Respective Methods of Judicial Selection

This Article analyzes detailed career-path and other demographic data to determine the extent to which the various judicial selection methods advance diverse candidates to the bench. The results show many similaritiesamong the mix of objective characteristics found on appellate benches across the states, regardless of selection method, but there are some important differences ... Part I discusses the history of judicial selection in the states and reviews the prior empirical and theoretical literature concerning judicial selection methods and the differences among judges produced by those selection methods, mainly with respect to gender, race, and localism. Part II identifies the data gathered for this analysis and describes the particulars of the five methods of judicial selection employed by the states. As noted above, many states elect their appellate judges; in other states, judges are chosen by a formal merit-selection protocol; and in two states, the legislature selects appellate judges. Prior studies categorized appellate judges in all the otherstates as simply “appointed.” Upon close review of the relevant legal mechanisms in those states, this Article concludes it is more appropriate to recognize that their judicial-selection protocols resemble those in merit-selection states, except that in these “merit-confirmation” states, the governor’s appointment power also is constrained by the requirement that a separate elected body, usually the legislature, must approve any appointee before he or she may take the bench. Part III describes the results of the analysis. The typical characteristics of the judges across all selection methods, including career paths, education and other factors, are discussed first. The analysis shows that, although appellate benches in merit-selection states look much like those in election states, judges in merit-confirmation states display some significant differences. Next, this Article addresses some implications of popular election of judges, including (1) differences between the characteristics of judges in election states and those in merit-selection and merit-confirmation states; (2) differencesin the characteristics of judges who first come to the bench in election statesby appointment, rather than by election; and (3) differences between benches produced by partisan elections and by non-partisan elections. Finally, this Article discusses the proportionate representation of women and non-whites on the various appellate benches