Function Of Photon Wavelength Research Articles

Green synthesized Al-metal complex to reduce the crystalline phase and improve the optical properties of CS based polymer blends

In the present study, a green coordination chemistry technique is used for the preparation of Aluminum complexes (Al3+-polyphenol complex) by using black tea extract solution. Chitosan: Poly(2-ethyl-2-oxazoline) (CS: POZ) composite samples loaded with Al3+-complex was arranged by solution casting technique. Various techniques were used to characterize the films, such as UV–Visible spectroscopy, fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The shifting of the peaks and their reduction in intensity in both XRD and FTIR confirmed the amorphous development with the loading of the Al3+-complex and the production of strong interaction between functional groups of the CS: POZ with the Al3+-complex, respectively. The insertion of the Al3+-complex into the host polymer matrix resulted in the creation of a polymer composite with controlled optical properties and improved optical parameters, including dielectric constant (εr), dielectric loss (εi) and refractive index (n). The complex dielectric constant's real and imaginary components as a function of photon wavelength were explored to derive various high-frequency characteristics. This includes extracting dielectric constant at short wavelength (ε∞), optical resistivity (ρopt), localized charge density values (N/m*), plasma angular frequency (ωp), optical mobility (μopt), and relaxation time (τ) of electrons, in which all these optical parameters are important for choosing suitable materials for optoelectronic applications. In accordance with (45 ml of Al3+-complex insertion), both ωpandN/m* magnitudes are enlarged up to 10-times, while the optical band gap is remarkably dropped (4.8–1.65 eV), which is calculated using Tauc's relation, and the electronic transition mode was identified by using optical dielectric loss (εi). Moreover, the Wemple–DiDomenico single oscillator model was applied to study the dispersion behavior of their refractive index and estimate the oscillator dispersion energy (Ed) and average oscillator energy (Eo) and parameters. The polymer composite with absorption performance in the visible region and other superior optical properties is fundamental for photo cells and commercialization in optoelectronic devices.

Characteristics of Poly(vinyl Alcohol) (PVA) Based Composites Integrated with Green Synthesized Al3+-Metal Complex: Structural, Optical, and Localized Density of State Analysis.

The influence of dispersing Al-metal complex on the optical properties of PVA was investigated using UV–visible spectroscopy. Polymer composite films with various Al3+-complex amounts in the PVA matrix were arranged by solution casting technique by means of distilled water as a widespread solvent. The formation of Al3+-metal complex was verified through Ultraviolet–visible (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR) examinations. The addition of Al-complex into the polymer matrix led to the recovery of the optical parameters such as dielectric constant (εr and εi) and refractive index (n). The variations of real and imaginary parts of complex dielectric constant as a function of photon wavelength were studied to calculate localized charge density values (N/m*), high-frequency dielectric constant, relaxation time, optical mobility, optical resistivity, and plasma angular frequency (ωp) of electrons. In proportion with Al3+-complex content, the N/m* values were amplified from 3.68 × 1055 kg−1 m−3 to 109 × 1055 kg−1 m−3. The study of optical parameters may find applications within optical instrument manufacturing. The optical band gap was determined from Tauc’s equation, and the type of electronic transition was specified. A remarkable drop in the optical band gap was observed. The dispersion of static refractive index (no) of the prepared composites was analyzed using the theoretical Wemple–DiDomenico single oscillator model. The average oscillator energy (Eo) and oscillator dispersion energy (Ed) parameters were estimated.

Effect of Annealing on the Structural and Optical Properties of Amorphous Ge8Se60Te30Sb2 Thin Films

Thin film of Ge8Se60Te30Sb2 was synthesized by conventional melt quench technique. The structural properties of the pre annealed and post annealed films were studied by XRD characterization. Once the Ge8Se60Te30Sb2 film is annealed in the temperature range of 373–413 K for 2 h, it is observed that there is a continuous change in structure and formation of some polycrystalline structures in the amorphous phases. The optical transmission of these films was studied in the range 300–1000 nm as a function of photon wavelength. The band gap value suggests that sample is a semiconductor. The optical band gap Eg was observed to decrease in the range 373–413 K with increasing annealing temperature. The absorption coefficient (α) and extinction coefficient (k) were also evaluated. Annealing induced effect on the optical parameters was described on the basis of defect states and density of localized states arises from amorphous to crystalline phase transformation.

Effect of annealing on the optical properties of amorphous Se79Te10Sb4Bi7 thin films

Thin films of Se79Te10Sb4Bi7, were prepared by Electron beam deposition technique. The structure of the as-prepared and annealed films has been studied by X-ray diffraction and the surface morphology by the scanning electron microscope (SEM). These studies show that there is a gradual change in structure and the formation of some polycrystalline structures in the amorphous phases is observed when the Se79Te10Sb4Bi7 film is annealed in the temperature range of 333–393K. The optical transmission of these films has been studied as a function of photon wavelength in the range 300–2500nm. It has been found that the optical band gap Egopt decreased with increasing annealing temperature in the range 333–393K. The Urbach energy (Eu), optical conductivity (σopt), imaginary (εi), and real (εr) parts of the complex dielectric constant (ε) and lattice dielectric constant (εL) were also determined. The changes noticed in optical parameters with increasing annealing temperature were explained on the basis of structural relaxation as well as change in defect states and density of localized states due to amorphous-crystalline transformation.

Structural and optical investigations of Cd 1 − x Zn xTe thin film

Thin films of Cd 1 − x Zn xTe (x = 0.02, 0.04, 0.06, 0.08, 0.10) were prepared by vacuum evaporation technique in a base pressure of 10 − 5 Torr on well-cleaned glass substrates. XRD and SEM were used to study the structure of as-deposited and annealed films. These studies show that there is no appreciable change in structure when films were annealed in the temperature range of 300–400 K, however, when annealed above 400 K the formation of some polycrystalline structures is seen in the amorphous phases. The transmittance and absorbance of the as-deposited films were measured in the spectral range of 400–1000 nm. The dependence of the absorption coefficient on the photon energy is well described by the relation αhν = B (hν − E o) 2. The optical transmission of these films has been studied as a function of photon wavelength. It has been found that the optical band gap first increases with annealing temperature up to 600 K thereafter decreases continuously with increase in annealing temperature and sharply decreases near crystallization temperature.

Characterisation of a silicon photomultiplier device for applications in liquid argon based neutrino physics and dark matter searches

The performance of a silicon photomultiplier has been assessed at low temperature in order to evaluate its suitability as a scintillation readout device in liquid argon particle physics detectors. The gain, measured as 2.1 × 106 for a constant over-voltage of 4V was measured between 25°C and -196°C and found to be invariant with temperature, the corresponding single photoelectron dark count rate reducing from 1MHz to 40Hz respectively. Following multiple thermal cycles no deterioration in the device performance was observed. The photon detection efficiency (PDE) was assessed as a function of photon wavelength and temperature. For an over-voltage of 4V, the PDE, found again to be invariant with temperature, was measured as 25% for 460nm photons and 11% for 680nm photons. Device saturation due to high photon flux rate, observed both at room temperature and -196°C, was again found to be independent of temperature. Although the output signal remained proportional to the input signal so long as the saturation limit was not exceeded, the photoelectron pulse resolution and decay time increased slightly at −196°C.

In situcleaning of metal cathodes using a hydrogen ion beam

Metal photocathodes are commonly used in high-field rf guns because they are robust, straightforward to implement, and tolerate relatively poor vacuum compared to semiconductor cathodes. However, these cathodes have low quantum efficiency (QE) even at UV wavelengths, and still require some form of cleaning after installation in the gun. A commonly used process for improving the QE is laser cleaning. In this technique the UV-drive laser is focused to a small diameter close to the metal's damage threshold and then moved across the surface to remove contaminants. This method does improve the QE, but can produce nonuniform emission and potentially damage the cathode. Ideally, an alternative process which produces an atomically clean, but unaltered, surface is needed. In this paper we explore using a hydrogen ion (H-ion) beam to clean a copper cathode. We describe QE measurements over the wavelength range of interest as a function of integrated exposure to an H-ion beam. We also describe the data analysis to obtain the work function and derive a formula of the QE for metal cathodes. Our measured work function for the cleaned sample is in good agreement with published values, and the theoretical QE as a function of photon wavelength is in excellent agreement with the cleaned copper experimental results. Finally, we propose an in situ installation of an H-ion gun compatible with existing s-band rf guns.

Reexamination of the photodissociation of NaH

We have recalculated the photodissociation cross section of NaH as a function of photon wavelength for the $X{}^{1}\ensuremath{\sum}^{\ensuremath{\rightarrow}}B{}^{1}\ensuremath{\Pi}$ transition using the time-independent Fermi golden rule. We have made an attempt to clarify the discrepancy between a recent calculation where the time-dependent autocorrelation function was employed and an earlier one where the Fermi golden rule was used.

Photon Energy and Photon Intermittence Effects on the Quantum Efficiency of Photoinduced Oxidations in Crystalline and Metastable TiO2Colloidal Nanoparticles

We report quantum yields φ-NP for the photocatalytic oxidation of 3-nitrophenol (NP) in clear, aerated, aqueous colloids of crystalline or metastable TiO2 nanoparticles as a function of photon wavelength (254 ≤ λ/nm ≤ 366) and photon absorption intermittence Iap (0.002 ≤ Iap/photons particle-1 s-1 ≤ 2). φ-NP's vary as φ-NP ∝ Iap-0.21±0.05 at all λ's in metastable TiO2 sols and are ∼20 times smaller than the Iap-independent φ-NP's determined in crystalline suspensions. Higher energy photons are always more efficient. We infer that (1) hyperthermal holes are able to capture electrons from NP while being deactivated in both types of particles, (2) thermalized electrons and holes are trapped in metastable particles within nanoseconds and persist as such for minutes, and (3) shallower traps become populated at larger Iap's. The similar action spectra of φ-NP and φ-S for nonchelating NP and bidentate salicylate (S) [E0(NP/NP+•) ≈ E0(S-/S•) ≈ 2.8 V vs NHE], in the presence or absence of phosphate as a competing ligand, are evidence that hot carrier effects are indeed associated with outer-sphere interfacial redox reactions. Our data support kSC,max ≥ 6 × 105 cm s-1 for h + NP → NP.+, which is close to the adiabatic coupling limit.

Dissociative photoionization of O 2 in the vuv region studied by photoion kinetic energy spectroscopy

Photoion kinetic energy spectra of O + produced by the dissociative photoionization of O 2 have been measured as a function of photon wavelength in the vacuum-uv region. which have shown both the non-Franck-Condon population of the vibrational O 2 + (B 2 ∑ g −) states near the ionization thresholds via both resonance-assisted photoionization and direct ionization.

Kerr rotations and anisotropy in (Pt/Co/Pt)/X multilayers

The link between interface sharpness and perpendicular magnetic anisotropy (K/sub /spl perp//) in Pt/Co multilayers has been exploited to yield enhanced magnetic anisotropy in related multilayer structures. These new multilayers consist of a (Pt/Co/Pt)/Pd stacking sequence where the Pt thickness is of just one atomic monolayer. The extra interfaces per period are introduced in areas where the spin polarization is still expected to be large thus resulting in extra magnetic anisotropy. K/sub /spl perp// as high as 5/spl times/10/sup 7/ erg/cm/sup 3/ was measured in Xe sputtered films with this new period. This idea was extended to (Pt/Co/Pt)X systems with X=Ag, Cu, Ni. A ten fold increase in K/sub /spl perp// is observed in these films compared to their respective Co/X counterparts. The Kerr rotation (/spl theta/K) as a function of photon wavelength is also greatly enhanced by the presence of the Pt monolayers. A strong dependence of /spl theta/K on the spacer element X in these systems is observed.

Electron-Impact Induced Molecular Fluoresence Spectroscopy

Abstract By the bombardment of gaseous molecules with monoenergetic electrons the molecules can be electronically excited and/or fragmented, depending upon the energy supplied by the electrons. Any fragments which may be produced also have the possibility of being produced in electronically (as well as vibrationally and rotationally) excited states. The electronically excited molecules and fragments both possess the possibility of radiative decay (fluorescence). The measurement of this fluorescence as a function of both electron energy and photon wavelength is termed “electron-impact induced fluorescence spectroscopy.” A plot of fluorescence intensity as a function of the electron energy at a given photon wavelength is generally referred to as an “excitation function,” which is exactly analogous to the excitation spectrum which can be obtained in conventional (optically excited) fluorescence spectrometry. A plot of the fluorescence intensity as a function of photon wavelength at a given electron energy is...

Photoelectron spectra and partial photoionization cross-sections for carbon dioxide

A photoelectron spectrometer has been used to determine partial photoionization cross-sections for carbon dioxide for monochromatic incident radiation throughout the wavelength range 584–720 Å. Transitions to particular states of the CO + 2 ion were identified by measuring the photoelectron energy. Transitions to the 2π g , 2π u , 2Σ + u and 2Σ + g states of CO + 2 were observed at all photon energies for which they were energetically allowed. Partial cross-sections for the production of each of these ionic states have been determined as a function of photon wavelength.