Arza Ron

Effectively left-handed (negative index) composite material

We show that a layered material, with alternating layers having negative permittivity (e<0) and negative permeability (μ<0), responds to electromagnetic fields in many ways like a homogeneous left-handed material with e<0 and μ<0. In particular, such a layered structure supports electromagnetic waves with group velocity antiparallel to the phase velocity. However, phase-sensitive measurements of the scattering matrix would distinguish the material from a homogeneous left-handed material. The appearance of a mode with positive index of refraction (right-handed mode) at frequencies for which e and μ are negative is a surprising feature.

Lattice Vibrations of the Solids N2, CO2, and CO

The far‐infrared absorptions of the solids N2, CO2, and CO have been investigated. Two bands were observed for each solid below 100 cm−1 and the spectrum observed for CO2 is in good agreement with that reported previously. The frequencies for N2 have been found to be in good agreement with calculations based on the theory described by Walmsley and Pople. The absorption intensities have been calculated from the theory described in the preceding paper. The experimental values available for the intensities are uncertain to within a factor of 3 and the calculated and measured values agree well within this limit. It is concluded that the intensity theory has been shown to be valid to better than within a factor of 2 but a more precise test is contingent on the availability of more accurate experimental measurements. From the lack of agreement between calculated and observed intensity ratios between the absorption bands of the same substance, it is concluded that the quadrupole—quadrupole term is not adequate t...

Storing images in warm atomic vapor.

Reversible and coherent storage of light in an atomic medium is a promising method with possible applications in many fields. In this work, arbitrary two-dimensional images are slowed and stored in warm atomic vapor for up to 30 micros, utilizing electromagnetically induced transparency. Both the intensity and the phase patterns of the optical field are maintained. The main limitation on the storage resolution and duration is found to be the diffusion of atoms. A technique analogous to phase-shift lithography is employed to diminish the effect of diffusion on the visibility of the reconstructed image.

Vibrational Spectra of Group IIB Halides. II. The Halides of Cadmium and Mercury

The infrared spectra of the vapors of all cadmium and mercury halides were studied at low temperatures by matrix isolation. The spectra are classified into four absorption regions recorded in the 800–35‐cm−1 range. The highest and lowest frequencies are assigned to the antisymmetric stretching mode and the doubly degenerate bending modes, respectively, of the MX2 molecules. The nature of the bonding in the molecule is discussed and statistically calculated entropy values are compared with corresponding values obtained from thermochemical measurements.

Infrared spectrum of liquid and crystalline ammonia

Abstract The vibrational spectra of liquid ammonia and of the solid, grown from the melt under equilibrium conditions, were measured at several temperatures in the range 202–77 K. Some new absorption features were observed. The controversy regarding reported spectra of cubic phase was resolved unambiguously.

Vibrational Spectra and Thermodynamics of the Zinc Halides

The infrared absorption spectra of the four zinc halides have been investigated by the low‐temperature matrix‐isolation technique. The spectral range 800–35 cm−1 has been covered. Four absorption regions have been observed in all cases. The highest energy region is structured and represents the antisymmetric stretching frequency ν3. The structure has been fully characterized as due to molecules of different isotopic compositions. The second and third absorption regions have been demonstrated to be due to higher polymers by means of double‐oven experiments. The lowest‐frequency absorption has been assigned as the bending vibration ν2. Statistical calculations of the molecular entropies have been carried out on the basis of the new results, and these entropy values are found to be in excellent agreement with third‐law entropy values where available.

Raman Spectrum of α‐N2

The Raman spectrum of solid α‐N2 has been investigated between 12°–35.5°K. Two lines were observed at 31.5 and at 35.8 cm−1, with intensity ratio 3.6 in favor of the lower‐frequency line. A calculation of the scattering intensities was carried out assuming additivity of molecular polarizabilities. Consideration of relative intensities led to the assignment of the three predicted Raman‐active librational lattice vibrations, assuming a close coincidence of two of these modes. The assignment is supported by an independent frequency calculation.

Resonant Raman scattering in nanoscale pentacene films

Resonant Raman scattering intensities from nanoscale films of pentacene display large resonant enhancements that enable observation of vibrational modes in monolayer cluster films. The resonant enhancements occur when the outgoing photon energy overlaps the free exciton optical transitions observed in luminescence. The results point to the significant potential of resonant Raman methods in the characterization of nanoscale structures of organic molecular semiconductors.

Far‐Infrared Spectrum of HCl Dimers

HCl absorptions have been observed in the wavelength region 150–250 cm−1 in solid rare‐gas solutions. From the dependence of the absorption intensity on sample preparations it is concluded that these spectra are due to polymers formed on condensation. In solid xenon, the isotopic pattern of the spectrum requires the assignment to cyclic dimer molecules of HCl. In the other solid solutions additional bands appear in this region, which have not been definitely assigned. The hydrogen‐bond stretching force constant has been calculated from the measurements.

Far‐Infrared Spectra of Ethane, Ethylene, and Acetylene

The far‐infrared spectra of crystalline C2H6, C2D6, C2H4, C2D4, C2H2, and C2D2 have been recorded at various temperatures between 25 and 140°K. Each compound showed two absorption bands which were shown to be due to translational lattice modes. Upon heating, these bands broadened and decreased in intensity; they were also displaced toward lower frequencies by about 0.1 cm−1/°K. For ethylene an analysis was carried out based on the “diatomic potential.” Here each molecule was assumed to consist of a pair of centers separated by an effective distance d, each center interacting, through a Lennard‐Jones‐type potential, with the centers in all neighboring molecules. Frequencies and thermal frequency shifts were calculated as a function of d, and good agreement was attained with the observed values for ethylene, with d = 1.04 A.The far‐infrared spectra of crystalline C2H6, C2D6, C2H4, C2D4, C2H2, and C2D2 have been recorded at various temperatures between 25 and 140°K. Each compound showed two absorption bands which were shown to be due to translational lattice modes. Upon heating, these bands broadened and decreased in intensity; they were also displaced toward lower frequencies by about 0.1 cm−1/°K. For ethylene an analysis was carried out based on the “diatomic potential.” Here each molecule was assumed to consist of a pair of centers separated by an effective distance d, each center interacting, through a Lennard‐Jones‐type potential, with the centers in all neighboring molecules. Frequencies and thermal frequency shifts were calculated as a function of d, and good agreement was attained with the observed values for ethylene, with d = 1.04 A.