Energy transport in high-density spin-exchange optical pumping cells

We present in situ measurements of temperatures inside multi-atmosphere spin-exchange optical pumping cells using Raman scattering from the N2 quenching gas. Under conditions usually prevailing in spin-exchange optical pumping experiments, we find that gas temperatures can be elevated hundreds of degrees above ambient, and that convection plays a very important role in the heat transport of the system.     

First results from laser spectroscopy on bunched radioactive beams from the JYFL ion-beam cooler

A new RFQ ion-beam cooler and buncher, installed after the mass-separating magnet of the ion guide isotope separator, IGISOL, JYFL, has dramatically increased the scope of on-line laser spectroscopy at this facility. The device, operated in a bunching mode, has permitted new measurements on short-lived radionuclei in the Ti, Zr and Hf chains at a sensitivity two orders of magnitude greater than that previously achieved. The device has also opened new prospects for laser-based nuclear spectroscopy at the facility, particularly collinear resonance ionisation spectroscopy. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: pc@mags.ph.man.ac.uk     

Total cross-section measurements for 2–400 eV positrons in the rare gases

Experimentally determined values of the total scattering cross-sections for positrons in the energy range 2–400 eV on He, Ne, Ar, Kr and Xe are presented.     

Using Estimated Missing Spatial Data with the 2-Median Model

Spatial operations research problems seek best locations, often points of minimum aggregate weighted distance, requiring georeferenced data as input. Frequently maps of such data are incomplete, with holes in their geographic distributions. Spatial statistical procedures are available to complete these data sets with best estimates of the missing values. Impacts such imputations have on 2-median facility location–allocation solutions are explored. The sampling distribution of the spatial mean and standard distance of these medians are studied. Population density is used as the weight attribute in determining location-allocation solutions because it can be accurately described with a relatively simple spatial statistical model.     

Eulogy: Henri Cartan

At Encaenia on 25th June, 1980, Henri Cartan, Professor Emeritusof Mathematics at the University of Paris, Honorary Member ofthe London Mathematical Society, was presented to the Chancellorof the University of Oxford for admission to the Honorary degreeof Doctor of Science. The editors are grateful to the Secretaryand Delegates of the Oxford University Press and to J. G. Griffith,the University Orator, for permission to reprint the addressdelivered on that occasion.     

The electronic spectrum of Dewar benzene

The electronic spectrum of Dewar benzene [bicyclo (2.2.0) hexa-2,5-diene] consists of two transitions above 185 nm. The lower energy transition is structureless and broad with a maximum at 205 nm. The other system begins around 200 nm and shows initially well-defined vibronic structure on a background of increasing continuous absorption, but becomes structureless by 185 nm. Arguments are presented that the two excited states involved in the spectrum are ¹A₂ arising from a $\text{π-π}{}^1$ excitation, and ¹B₁ from a $\text{σ-π}{}^1$ excitation involving the strained σ-bridge bond in Dewar benzene. The interrelationships both photochemical and photophysical of the (CH)₆ potential surface are discussed.