Light source spectrum, brightness perception and visual performance in pedestrian environments: A review

This review considers the impact of light source spectral power distribution (SPD) on brightness perception and visual performance in mesopic conditions, with emphasis on the comparison of metal halide (MH) and high pressure sodium (HPS) lamps. Models of mesopic vision predict that SPD is a significant variable in that at a HPS photopic luminance of 0.100 cd/m, MH need only produce about 0.070-0.075 cd/m to be seen as equally bright. However, attempts to validate the predictions of these models in the field have met with mixed success. As for visual performance, experimentation has shown that there are effects of SPD in mesopic conditions, but the magnitude of these effects depends on the nature of the task. Three alternative approaches are suggested for comparing light sources with different SPDs in mesopic conditions. © The Chartered Institution of Building Services Engineers 2005

Investigating the chromatic contribution to recognition of facial expression

A pedestrian may judge the intentions of another person by their facial expression amongst other cues and aiding such evaluation after dark is one aim of road lighting. Previous studies give mixed conclusions as to whether lamp spectrum affects the ability to make such judgements. An experiment was carried out using conditions better resembling those of pedestrian behaviour, using as targets photographs of actors portraying facial expressions corresponding to the six universally recognised emotions. Responses were sought using a forced-choice procedure, under two types of lamp and with colour and grey scale photographs. Neither lamp type nor image colour was suggested to have a significant effect on the frequency with which the emotion conveyed by facial expression was correctly identified

Collinear laser spectroscopy of atomic cadmium

Hyperfine structure $A$ and $B$ factors of the atomic $5s\,5p\,\; ^3\rm{P}_2 \rightarrow 5s\,6s\,\; ^3\rm{S}_1$ transition are determined from collinear laser spectroscopy data of $^{107-123}$Cd and $^{111m-123m}$Cd. Nuclear magnetic moments and electric quadrupole moments are extracted using reference dipole moments and calculated electric field gradients, respectively. The hyperfine structure anomaly for isotopes with $s_{1/2}$ and $d_{5/2}$ nuclear ground states and isomeric $h_{11/2}$ states is evaluated and a linear relationship is observed for all nuclear states except $s_{1/2}$. This corresponds to the Moskowitz-Lombardi rule that was established in the mercury region of the nuclear chart but in the case of cadmium the slope is distinctively smaller than for mercury. In total four atomic and ionic levels were analyzed and all of them exhibit a similar behaviour. The electric field gradient for the atomic $5s\,5p\,\; ^3\mathrm{P}_2$ level is derived from multi-configuration Dirac-Hartree-Fock calculations in order to evaluate the spectroscopic nuclear quadrupole moments. The results are consistent with those obtained in an ionic transition and based on a similar calculation.Comment: 12 pages, 5 figure

Laser Spectroscopy of Niobium Fission Fragments: First Use of Optical Pumping in an Ion Beam Cooler Buncher

A new method of optical pumping in an ion beam cooler buncher has been developed to selectively enhance ionic metastable state populations. The technique permits the study of elements previously inaccessible to laser spectroscopy and has been applied here to the study of Nb. Model independent mean-square charge radii and nuclear moments have been studied for $^{90,90 m,91,91 m,92,93,99,101,103}$Nb to cover the region of the N=50 shell closure and N≈60 sudden onset of deformation. The increase in mean-square charge radius is observed to be less than that for Y, with a substantial degree of β softness observed before and after N=60