Gene O. Carlisle

Synthesis, magnetic and structural properties of the nickel(II) tartrate complex, Ni6(dl-C4H4O6)7·30H2O

Abstract The synthesis, magnetic and structural properties of the polymeric nickel(II) tartrate complex, Ni 6 ( dl -C 4 H 4 O 6 ) 7 ·3H 2 O, are described. The magnetic susceptibility has been determined over the temperature range 300-77°K, and the data were described by the Curie law. Other physical data including electronic spectral, i.r., and X-ray were taken and are in agreement with a polymeric octahedral structure.

Electric-field enhancement and modulation of permanent grating diffraction in dye and carbon nanotube-doped liquid crystal

Permanent gratings were written, without the aid of external fields, in planar nematic liquid crystal cells doped with only Methyl Red (MR) as well as cells doped with both Methyl Red and single-wall carbon nanotubes (CNTs). Grating formation based on trans-cis photoisomerism of MR followed by surface adsorption of the cis-isomer was attempted. The diffraction efficiency was easily enhanced and modulated by application of ac fields covering wide ranges of frequency and voltage; thus, allowing for tuning the diffracted signals. Cells doped with MR and CNTs had a maximum relative diffraction efficiency of 67% while cells doped only with MR exhibited a maximum of 28%. The maximum diffraction efficiency appears to be associated with the Freedericksz threshold voltage. The permanent gratings are robust and have remained stable for over two years.

Polarization-independent photochromic diffraction in a dye-doped liquid crystal

We report the observation of polarization-independent photochromic diffraction in an azo-dye-doped liquid crystal. The generation of the phase grating is more than 90% independent of the polarization of the writing beams, and the diffraction by the phase grating is more than 90% independent of the polarization of the probe beam. Unpolarized lamp light was also used to generate real-time phase gratings and self-diffraction. For the first time to our knowledge, photochromic phase modulation and light diffraction that exhibit more than 90% polarization independence for both writing and probe beams were produced in an anisotropic liquid-crystalline material.

Polymer-enhanced diffraction in an azo-dye-doped liquid crystal

Degenerate four-wave mixing measurements were employed to obtain first-order diffraction efficiencies of dye-doped and polymer- dye-doped liquid crystals. A sixfold enhancement in the diffraction effi- ciency (12%) was found for the liquid crystal doped with 1% azo dye and 1% polymer, compared to a 2% diffraction efficiency found for the liquid crystal containing 1% azo dye. Polarization dependence of absorption and diffraction studies, coupled with the absence of two-beam coupling, support a grating formation based on photoisomerization of azo dye mol- ecules, which leads to a reorientation of the liquid crystal phase.

Synthesis and magnetic properties of bis[2-(4-isobutylphenyl)propionato]copper(II)

Abstract This paper reports the synthesis and magnetic properties of the copper(II) complex of the antiinflammatory drug ibuprofen which is 2-(4-isobutylphenyl)propionic acid. Cryomagnetic and EPR measurements on bis[2-(4-isobutylphenyl)propionato]copper(II) indicate the compound to be dimeric with a structure such as that for copper acetate. A least-squares fitting procedure yielded the magnetic parameters g = 2.17 and 2J = − 339 cm −1 .

Large stable second‐harmonic coefficients in an azo‐dye attached polymer oriented by corona poling

Second‐harmonic generation and spectroscopic absorption measurements were made over a 15‐month period to study the nonlinear‐optical thin‐film properties of an azo‐dye attached polymer in which the dye chromophores were oriented by corona poling. Stable, resonance‐enhanced values of the nonlinear optical coefficient d33 for the fundamental of 1.064 μm were as high as 68 pm/V. The stabilized order parameter, calculated from absorbance measurements, was found to be 0.51 for the chromophores.

Magnetic properties of N,N′-ethylenebis(salicylideneiminato) copper(II)

Abstract This paper reports the electron paramagnetic resonance spectra and magnetic susceptibility data on N,N′-ethylenebis(salicylideneiminato)copper(II). The results show that the ground state of the complex is of triplet multiplicity with the first excited state being a singlet, at 18·5 cm −1 higher in energy. EPR measurements confirm the existence of spin-spin coupling, and a value of D = 0·0365 cm −1 was obtained from the low-field parallel lines. The g value obtained from the triplet state spectra were g ∥ = 2·244, g ⊥ = 2·025, and 〈g〉 = 2·098. Cryomagnetic measurements for the low-temperature range 3·7–61°K in conjunction with a best fitting procedure yielded the magnetic parameters 2 J = +18·5 cm −1 and π = −2·15°K. A superexchange mechanism based on both intraatomic and interatomic electron transfer is proposed to account for the experimental data.

Effects of carbon nanotubes on electro-optical properties of dye-doped nematic liquid crystal

Electro-optical effects of planar nematic liquid crystal cells doped with dye and carbon nanotubes (CNTs) were investigated by utilizing the absorption property of the dye. Voltage-dependent transmittance and hysteresis measurements under applied ac and dc fields were presented. Cells doped with both Methyl Red and CNTs showed increased conductivity and capacitance, slower ac-rise switching time and dc-backflow on turn-off. The cells exhibited little hysteresis but those containing CNTs reduced residual dc by about 50%. First-order probe diffraction of permanent gratings revealed a correlation of ac-field-enhanced diffraction efficiency and Fréedericksz threshold voltage.

Preparation and optical properties of a poly(N-vinylcarbazole) material

We report on the photorefractive properties of a stable polymeric material based on the host polymer, poly(N-vinylcarbazole). Two-beam coupling and four-wave mixing experiments were used to measure the performance of devices constructed by sandwiching the material, composed of host, plasticizer, photo-sensitizer, and non-linear optical chromophore, between transparent electrodes. A steady-state diffraction efficiency of 60% and a two-beam coupling gain of 22 cm−1 in excess of the absorption of 4 cm−1 were observed at the lasers operating wavelength of 670 nm. The devices are easily prepared and have lifetimes in excess of one year with no indication of degradation when stored at ambient temperatures.

Enhanced second-harmonic response and stability of corona-poled guest—host polycarbonate thin films

Second-harmonic generation and spectroscopic absorption measurements were made to study the non-linear optical and stability properties of guest/host polycarbonate thin films in which the guest chromophores were oriented by corona poling. Optimum poling conditions were achieved at temperatures less than the glass-rubber transition temperatures. Stabilized order parameters as high as 0.23 and retention of orientational order as high as 86% were found. Stable, resonance-enhanced, values of the non-linear optical coefficient d33, for the fundamental of 1.064 Μm, were as high as 31 pm V−1. This value is over four times that predicted by a simple thermodynamic model for isotropic materials. Hydrogen bonding between the guest and polycarbonate is proposed to account for the high d33 coefficients and long-term stability of the films.