Tour of the Electromagnetic Spectrum Booklet

This booklet introduces electromagnetic waves, their behaviors, and how scientists visualize these data. Each region of the spectrum is described and illustrated with examples of NASA science. It is a companion piece to the video series under the same title. Educational levels: Informal education

Vibrational nonequilibrium effects in the conductance of single-molecules with multiple electronic states

Vibrational nonequilibrium effects in charge transport through single-molecule junctions are investigated. Focusing on molecular bridges with multiple electronic states, it is shown that electronic-vibrational coupling triggers a variety of vibronic emission and absorption processes, which influence the conductance properties and mechanical stability of single-molecule junctions profoundly. Employing a master equation and a nonequilibrium Green's function approach, these processes are analyzed in detail for a generic model of a molecular junction and for benzenedibutanethiolate bound to gold electrodes.Comment: 5 pages, 4 figure

Vibronic effects on resonant electron conduction through single molecule junctions

The influence of vibrational motion on electron conduction through single molecules bound to metal electrodes is investigated employing first-principles electronic-structure calculations and projection-operator Green's function methods. Considering molecular junctions where a central phenyl ring is coupled via (alkane)thiol-bridges to gold electrodes, it is shown that -- depending on the distance between the electronic $\pi$-system and the metal -- electronic-vibrational coupling may result in pronounced vibrational substructures in the transmittance, a significantly reduced current as well as a quenching of negative differential resistance effects.Comment: Submitted to Chem. Phys. Lett. (13 pages, 5 figures) this version: typos and formating correcte

TV Channels, Self Control and Happiness

In many countries, TV viewers have access to more and more TV channels. We study whether people can cope with this and watch the amount of TV they find optimal for themselves or whether they are prone to over-consumption. We find that heavy TV viewers do not benefit, but instead report lower life satisfaction when exposed to more TV channels. This finding runs counter to the standard economic prediction that a larger choice set does not make people worse off. It suggests that an identifiable group of persons experience a self-control problem when it comes to TV viewing.Self-control, over-consumption, life satisfaction, experienced utility, TV viewing

A Simple Modification of DC Current Septa to Reduce Current Density by Half

Circular accelerators typically have one injection and one extraction septum magnet. CEBAF is a recircuating electron linac which has a total of 27 DC current septa and one Lambertson. Current densities range from 28-48 A/mm 2 . Current sheet widths are 5-24 mm, turns count 5-24 and lengths 1000-3000 mm. A design exercise to increase the beam energy to 22 GeV is underway. Since doubling the current density in copper is not practical in the CEBAF layout a conductively cooled superconducting septum concept was examined. Putting the current sheet and its cryostat between the poles as in a standard current sheet septum would have required 90 mm pole gap. The poles were brought to 40 mm separation and the steel notched for the 90 mm cryostat. The field in the bore increased while the field outside the current sheet remained close to zero as in a conventional septum. Required current density dropped enough that a copper coil became possible. Two examples will be shown, the one discussed above and the modification of the 3000 mm septum with 0.92 T bore field.Comment: 10 pages, 11 figures, Prepared for submission to JINS