E. T. Arakawa

Optical properties of glassy carbon from 0 to 82 eV

Optical constants have been obtained for glassy carbon from 0 to 82 eV by means of reflection measurements. The data have been analyzed by analogy with those for graphite in terms of single electron excitations and of collective oscillations of the π and σ electrons.

Optical Properties of Magnesium Fluoride in the Vacuum Ultraviolet

The room temperature optical properties of single crystal MgF2 were determined in the 4.1 eV–10.9 eV energy range, from transmission and near‐normal‐incidence reflectance measurements, and in the 11.0 eV–27.5 eV range, from reflectance measurements made at various angles of incidence. Sharp structure in the reflectance spectra of single crystal MgF2 is associated with an exciton transition at 11.8 eV. Broader structure at higher energies is associated with an interband transition at 20.8 eV. The energy‐loss function for volume plasmons has a maximum at 24.5 eV which agrees well with the theoretical value. In addition, the optical properties of an evaporated film were determined in the range 11.0 eV to 29.5 eV, but structure in the reflectance spectrum is not as well defined. However, there is fair agreement with previously published optical constants of evaporated MgF2.

Optical Properties of Single‐Crystal Magnesium Oxide

The reflectance of single crystals of MgO was measured at a 15° angle of incidence for photon energies between 4 and 29 eV and the optical constants obtained by a Kramers‐Kronig analysis of the reflectance data. In the energy range 4–14.5 eV, structure in the reflectance is in good agreement with that already reported. Reflectance measurements have not been previously reported above 14.5 eV. Peaks in the optical conductivity locate the Γ exciton at 7.65 eV and interband transitions at 11.0, 13.2, 14.9, 17.0, ∼19, 20.8, and ∼24 eV. The absorption edge for band‐to‐band transitions is estimated to be at 7.9 eV. The calculated energy‐loss function −Im(e+1)−1, where e is the dielectric constant, shows a maximum at 21.3 eV while the calculated loss function −Ime−1 shows a maximum at 22.4 eV and a subsidiary maximum at 25.4 eV. It is suggested that these maxima in −Ime−1 correspond to volume plasma resonances involving 6 and 8 electrons per molecule, respectively. The volume plasma energies calculated on the ass...

Optical Properties of MgO and MgF2 in the Extreme Ultraviolet Region

Measurements of the optical properties of MgO and MgF2 have been extended from 29 to 80 eV. Reflectance and emission spectra were obtained for single crystals and transmittance spectra for thin films. The extinction coefficients for single crystals of MgO and MgF2 are relatively large (>0.07 up to 80 eV), and sum‐rule calculations show the values to be reasonable. Structures in the extinction coefficients are identified as due to interband transitions from the core electron states to the conduction bands and to excitons associated with the Mg 2p to conduction‐band transitions in the two materials. The optical constants are used to identify the nature of characteristic energy losses reported in the literature. The extinction coefficients of thin films of MgO and MgF2 are less than for the single crystals.

Charge-transfer-induced changes in the electronic and lattice vibrational properties of acceptor-type GICs

Abstract We report on several charge-transfer-induced changes in the electronic and phonon properties of stage 1 and 2 graphite-H2SO4: c-axis LO and LA phonon dispersion, E2g (q = 0) intralayer graphitic phonon frequency, and resonant Raman scattering from the E2g modes. The data are discussed in terms of microscopic models.

Optical thin-film interference effects in microcantilevers

We report direct observation of thin-film interference effects in microcantilevers, an effect that can impact the optical monitoring of the microcantilever motion. When microcantilevers are illuminated with different wavelengths of light the amount of absorption and the wavelengths of maxima in the absorption depend upon the thickness of the layers, the materials used in the layers, and the direction of illumination. Wavelengths of maximum absorption are observed as microcantilever deflections due to heat-induced bending of the bimaterial structure of the microcantilever. Results are presented for different multilayer configurations and illumination directions. These results are then compared with theoretical calculations based on multilayer thin-film analysis.

Resonant interband raman scattering in metals and semimetals

Abstract A resonance has been observed in the Raman cross section for scattering from intralayer phonons in the quasi two-dimensional, metallic graphite intercalation compounds. The resonance is found to occur for photon energies which coincide with the threshold for electronic interband absorption. The cross section is observed to correlate with the frequency derivative |dϵ2/dω|2, where ϵ2 is the imaginary part of the dielectric function. Theoretical calculations suggests the resonance should be observed in all Raman-active metals and semimetals.

Optical Properties of Vacuum‐Evaporated Selenium and Tellurium

The optical properties of evaporated films of Se and Te at room temperature have been determined in the energy range from 5–25 eV. In addition the real part of the refractive index has been determined for Te up to 38 eV. The films used were of high quality, prepared and measured in vacuum (<2×10−5 Torr), and reflectances were significantly higher than reported in previous literature. The optical properties of Se and Te are similar; both show structure in the imaginary part eZ of the dielectric constant e between 7 and 9 eV identified with interband transitions. The calculated energy‐loss function ‐ Im(e+1)−1 shows a maximum at 14.5 eV in Se and at 11.3 eV in Te. The calculated energy‐loss function ‐ Im(e)−1 shows peaks at 5.25 and between 18.5 and 19.0 eV for Se and at 5.6 and 17.2 eV for Te. These optical data agree with published characteristic electron‐energy‐loss measurements and allow identification of the modes of energy loss involved.