Coupled Modes With A1 Symmetry In Tetragonal Batio3

The infrared properties of a system of first-order-coupled phonons are analyzed. The dielectric function and the Raman line shape of the polariton modes are derived. The parameters involved in the theory can be obtained from the Raman spectra of the TO and LO modes or from the Raman spectrum of the TO modes plus infrared-reflectivity measurements. It is shown that we can objectively distinguish real coupling from imaginary, contrary to the current belief. Numerical calculations are performed for the A1-symmetry modes of tetragonal BaTiO3, with good agreement for the polariton shapes and complete disagreement for the infrared reflectivity; damage at the crystal surface is pointed out as the probable cause of the discrepancy. In addition to the coupling between the lowest and the middle mode, previously known, a much larger coupling between the middle mode and the highest is shown to exist. Both couplings are shown to be real or nearly so. The discrepancy between the dielectric constant created by the resonant modes (electronic plus phonons) and the value obtained by electrical measurements is interpreted as a new indication that the crystal has a dynamical disorder; this disorder could also be cause of an anomalous broadening observed in the lowest polariton. © 1974 The American Physical Society.10835223533Information, Control and Communication (INSTICC),Institute for Systems and Technologies o

Temperature Dependence Of Dipolar Modes In Ferroelectric Batio3 By Infrared Studies

Temperature dependence of A1 modes in tetragonal phase and F1u modes in cubic phase of BaTiO3 has been studied by ir (infrared) reflectivity measurements. The spectra have been analyzed using Kramers-Kronig analysis and the coupled-mode classical oscillator fit. The results are in excellent agreement with each other and are compatible with the earlier Raman measurements. Such a compatibility indeed favors the conclusion of Pinczuk et al. with regard to the interpretation of the broad peaks at 270 and 520 cm-1 in the Raman spectrum to be of first order. A critical analysis of the earlier work in BaTiO3 is presented. © 1980 The American Physical Society.2252396240

Genetic divergence and its implication in breeding of desired plant type in coriander -Coriandrum sativum L.-

Seventy germplasm lines of coriander (Coriandrum sativum L.) of diverse eco-geographical origin were undertaken in present investigation to determine the genetic divergence following multivariate and canonical analysis for seed yield and its 9 component traits. The 70 genotypes were grouped into 9 clusters depending upon the genetic architecture of genotypes and characters uniformity and confirmed by canonical analysis. Seventy percent of total genotypes (49/70) were grouped in 4 clusters (V, VI, VIII and IX), while apparent diversity was noticed for 30 percent genotypes (21/70) that diverged into 5 clusters (I, II, III, FV, and VII). The maximum inter cluster distance was between I and IV (96.20) followed by III and IV (91.13) and I and VII (87.15). The cluster VI was very unique having genotypes of high mean values for most of the component traits. The cluster VII had highest seeds/umbel (35.3 ± 2.24), and leaves/plant (12.93 ± 0.55), earliest flowering (65.05 ± 1.30) and moderately high mean values for other characters. Considering high mean and inter cluster distance breeding plan has been discussed to select desirable plant types

Manipulation of exciton and trion quasiparticles in monolayer WS2 via charge transfer

Charge doping in transition metal dichalcogenide is currently a subject of high importance for future electronic and optoelectronic applications. Here, we demonstrate chemical doping in the CVD-grown monolayer (1L) of WS2 by a few commonly used laboratory solvents by investigating the room temperature photoluminescence (PL). The appearance of distinct trionic emission in the PL spectra and quenched PL intensities suggests n-type doping in WS2. The temperature-dependent PL spectra of the doped 1L-WS2 reveal a significant enhancement of trions emission intensity over the excitonic emission at low temperature, indicating the stability of trion at low temperature. The temperature-dependent exciton-trion population dynamic has been modeled using the law of mass action of trion formation. These results shed light on the solution-based chemical doping in 1L-WS2 and its profound effect on the photoluminescence which is essential for the control of optical and electrical properties for optoelectronic applications

Cold cathode emission studies on topographically modified few layer and single layer MoS2 films

Nanostructured materials, such as carbon nanotubes, are excellent cold cathode emitters. Here, we report comparative field emission (FE) studies on topographically tailored few layer MoS2films consisting of ⟨0001⟩ plane perpendicular (⊥) to c-axis (i.e., edge terminated vertically aligned) along with planar few layer and monolayer (1L) MoS2films. FE measurements exhibited lower turn-on field Eto (defined as required applied electric field to emit current density of 10 μA/cm2) ∼4.5 V/μm and higher current density ∼1 mA/cm2, for edge terminated vertically aligned (ETVA) MoS2films. However, Eto magnitude for planar few layer and 1L MoS2films increased further to 5.7 and 11 V/μm, respectively, with one order decrease in emission current density. The observed differences in emission behavior, particularly for ETVA MoS2 is attributed to the high value of geometrical field enhancement factor (β), found to be ∼1064, resulting from the large confinement of localized electric field at edge exposed nanograins. Emission behavior of planar few layers and 1L MoS2films are explained under a two step emission mechanism. Our studies suggest that with further tailoring the microstructure of ultra thin ETVA MoS2films would result in elegant FE properties

Pressure-induced Phase Transition In -liio3

We report the first observation of a pressure-induced phase transition in LiIO3. A new phase appears when -LiIO3 is compressed hydrostatically at room temperature, beyond 50 kbar. This is a reversible first-order transition with negligible hysteresis. The new phase -LiIO3 cannot be obtained by heating or cooling either - or -LiIO3 or by compressing the former. We observe the transition by studying the evolution of the Raman spectrum of -LiIO3 as a function of pressure (1 bar-95 kbar). We also report a detailed study of the pressure dependence of Raman frequencies for -LiIO3. The regularities observed in the mode-Gr̈neisen parameters and other pressure coefficients for thephase give insight into the probable structure of the high-pressure phase. © 1983 The American Physical Society.2862985298

Intercalant Vibrations In Stage-1 Alcl3 Graphite

We report the observation of intramolecular vibrations in stage-1 AlCl3-intercalated graphite compounds. The results show that two species are simultaneously present: Al2Cl6 molecules and a layer of solid AlCl3. © 1992 The American Physical Society.461065866588AFOSR; U.S. Department of Energy; DE-AC05-06OR23177; DOE; U.S. Department of Energ

Effect of VAM fungi and bacterial biofertilizers on mulberry leaf quality and silkworm cocoon characters under semiarid conditions

The influence of VAM fungi and bacterial biofertilizer (BBF) with 50% reduction in the recommended dose of (N and P) chemical fertilizers on leaf quality traits of mulberry variety (S-13) and its impact on silkworm (PM ? NB4D2) growth and cocoon characters were studied under semi-arid conditions. Four different treatments were imposed i.e., T1: Control (only 100% NPK); T2: VAM (50% cut in P); T3: BBF (50% cut in N) and T4: BBF and VAM (50% cut in N and P). The results revealed that reduction (50%) in the dose of chemical fertilizers in T2, T3 and T4 did not affected the leaf quality traits or cocoon parameters, this may be due to the effect of microbial inoculants in these treatments, which had efficiently regulated the normal growth, metabolism and physiological activity in plants. Among the three-biofertilizer treatments, leaf quality, silkworm growth and cocoon parameters were found improved in T4 and was on par with T1 control. The dual inoculation (T4) proved economical and beneficial with regard to saving of 50 % cost of chemical fertilizers and improvement in soil fertility, leaf quality and cocoon parameters, thus this technology can be recommended to sericulture

The Raman spectrum of magnesium fluoride

The Raman spectrum of a single crystal of MgF2 has been investigated using the resonance radiation of mercury as exciter. The observed Raman lines are of frequency shifts 73, 90, 154, 165, 295, 405, 415, 560, 2 472 and 2 535 cm-1. An analysis of the vibration spectrum has been made taking into account the infrared data of Barker, and the force constants have been calculated. The force constants suggest that the structure of MgF 2 has considerable molecular character.On a étudié le spectre Raman d'un monocristal de MgF2, excité par la radiation de résonance du mercure. Les raies Raman observées correspondent à des déplacements de fréquence 73, 90, 154, 165, 295, 405,,415, 560, 2472 et 2535 cm-1. Ce spectre a été analysé à partir des données infrarouges de Barker, et les constantes de force ont été calculées. Les valeurs de ces constantes suggèrent un caractère fortement moléculaire de la structure de MgF2