Optical Properties of the Rubidium and Cesium Halides in the Extreme Ultraviolet

The absorption spectra of evaporated thin films of all rubidium and cesium halides in the 50- to 250-eV region are reported. In this range, transitions from the 3d shell of Rb+ and from the 4d and 4p shells of Cs+ can be seen, as well as some transitions from inner shells of the halogen ions. Besides the absorption fine structure near the threshold for inner-shell transitions, broad absorption structure is observed and explained as due to d→f continuum transitions. The number of effective electrons whose oscillator strength has been exhausted in our spectral region has been computed from the absorption data; it is particularly strong for materials containing either Cs or I. Differences in the spectra of materials with NaCl and with CsCl structure are discussed. The measurements were performed using the DESY electron synchrotron as a light source

Low-energy interband absorption in bcc Fe and hcp Co

We have examined the electronic structure of bcc Fe and single-crystal hcp Co by using optical absorptivity and thermoreflectance techniques for 0.2≤hν≤5 eV. The optical conductivities σ were calculated by Kramers-Kronig analyses. A prominent structure was observed in σ for Fe at 2.37 eV and a shoulder was observed near 0.8 eV; the latter structure was the dominant feature in the thermoreflectance spectrum. These were discussed in terms of minority-spin band interband absorption and spin-flip interband transitions. The anisotropic optical conductivities of hcp Co were discussed in terms of recent energy-band calculations

Thermoreflectance investigation of the antiferromagnetic and paramagnetic phases of Cr

Thermoreflectance measurements have been performed on Cr single crystals at several temperatures above and below the Néel temperature. We observe dramatic changes induced by the magnetic phase transition. In contrast, static optical data fail to show appreciable differences in the (0.5-5.0)-eV photon-energy range. Magnetic ordering gives rise to the disappearance of transitions involving specific regions of the Fermi surface. New critical-point absorptions appear at the boundaries of the new Brillouin zone in antiferromagnetic Cr. Most of the observed experimental features have been identified by comparison with recent band-structure calculations

Tanker Acquisition: A Systems Engineering Perspective

A short examination of air refueling, specifically its past, present, and future, offers valuable insight into the developmental needs of this critical capability. This article seeks not only to showcase an appreciation for the roots of air refueling but also to high- light the requirement for sound systems engineering in conjunction with the creativity and willingness to take risks, as exhibited by our forefathers in the field. These attributes are vital to furthering air- refueling technologies and capabilities as well as refining the some- what flawed tanker-procurement process employed today

Multiplet Structure below Threshold in Appearance-Potential Spectra—Lanthanum N4,5

We present the N4,5 appearance-potential spectrum of La. Structure exists at energies lower than the threshold energy for transitions terminating at the Fermi level. Several similarities between optical absorption spectra and our results are discussed. These results contradict the simple model usually used to interpret appearance-potential spectra and emphasize the need for a new theory