Optical properties and chemical behavior of Laser-dye Coumarin-500 and the influence of atmospheric corona discharges.

Structure elucidation of Coumarin-500 Laser-dye in cyclohexane at room temperature has been studied by UV-Vis, Raman, and FTIR spectroscopic techniques. Optical properties and chemical behavior under the influence of atmospheric positive electric pulsed corona discharges were also examined. The effects of UV-Vis irradiation changed some optical parameters, such as decrease in optical density on the absorption spectrum and formation of photoproducts, due to the chromaticity removal.

High resolution absorption spectrum of dianilino in the vapor phase.

Photophysical and photochemical properties of diradical in the first excited state is recorded for the very first time with the IR, band structure for dianilino molecule at room temperature, in the vapor phase. In this experiment high resolution absorption spectra of anilino free radical, dianilino, aniline in the vapor phase and silicon dioxide in the solid state were recorded by flash photolysis technique photographically. Silicon dioxide absorption band between 250 and 255 nm were also observed for the reaction cell, because the cell and windows of the cell material were spectrosilica grade fused quartz.

Triplet-triplet optical energy transfer from benzophenone to naphthalene in the vapor phase.

In principle the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the different relaxation channels. Initially, electronically excited benzophenone emits photons in the phosphorescence band of benzophenone and these emitted photons, as a stream of particles, are absorbed by the acceptor molecule naphthalene, then excited naphthalene phosphoresces. In this investigation, sensitized phosphorescence decay times in different conditions were measured for benzophenone-naphthalene system in the vapor phase.

Singlet-singlet intermolecular optical energy transfer from naphthalene to benzophenone in the vapor phase.

By using the exothermic energy transfer as a function of pressure, the rate constant for diffusion was evaluated for benzophenone/naphthalene and naphthalene/benzophenone systems. In principle the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the different relaxation channels. Initially, electronically excited naphthalene "S1" state emits photons in the fluorescence band of naphthalene and these emitted photons, as a stream of particles, are absorbed by the acceptor molecule benzophenone, then excited benzophenone fluoresces.

Reactions of high translational energy hydrogen atoms with propane.

The reactions of translationally excited deuterium atoms with propane have been investigated by use of photochemically produced atoms of 157kJmol(-1) initial energy. The reaction mechanism was tested by comparing the results for the DBr scavenged system to those where Br(2) was used as radical scavenger. Values were obtained for the fraction of atoms undergoing "hot" reaction on collision with propane, and the relative cross sections for the interaction of deuterium atoms with propane and DBr.

Quadrupole type mass spectrometric study of the abstraction reaction between hydrogen atoms and ethane.

The reactions of photochemically generated deuterium atoms of selected initial translational energy with ethane have been investigated. At each initial energy the relative probability of the atoms undergoing reaction or energy loss on collision with ethane was investigated, and the phenomenological threshold energy was measured as 30+/-5kJmol(-1) for the abstraction from the secondary C-H bonds. The ratio of relative yields per bond, secondary:primary was approximately 3 at the higher energies studied.

Optical T-T absorption of salicylidene-p-toluidine in solution.

The observation of triplet-triplet absorption of salicylidene-p-toluidine, is complicated by the possible colored isomer formation during the optical pumping. The short-lived (singlet-singlet) and long-lived (triplet-triplet) absorption spectra were recorded phographically by microsecond flash and nanosecond laser flash photolysis techniques. Salicylidene-aniline complexes were purified by repeated recrystallisation until further recrystallisation produced no further changes for X-ray diffraction pattern and optical absorption, emission properties.

Laser-induced temperature dependent triplet state lifetime of rubreneperoxide.

A number of photophysical properties of three different types of rubreneperoxides have been measured experimentally by flash spectroscopy technique, including the two-photon absorption, fluorescence, delayed fluorescence and temperature dependent triplet-triplet absorption spectra. Excited singlet and triplet state lifetimes are temperature dependent. Lowest triplet state lifetimes were measured from 77 K to 50 degrees C.

Yotta-photonic excitation spectroscopy of salicylidene-m-bromo-aniline.

The observation of triplet-triplet absorption and emission spectra of salicylidene-m-bromo-aniline in solution, is complicated by the possible colored isomer formation during the optical pumping for yotta-photonic excitation at room temperature. The short-lived (singlet-singlet) and long-lived (triplet-triplet) absorption spectra were recorded phographically by microsecond flash and nano-second laser flash photolysis techniques. Salicylidene-m-bromo-aniline complexes were purified by repeated recrystallization until further recrystallization produced no further changes for X-ray diffraction pattern and optical absorption, emission properties.

Structure elucidation of laser-dye coumarin-540A by joint application of X-ray diffraction, X-ray fluorescence, prompt fluorescence, UV and visible spectroscopy.

X-ray, ultraviolet, and visible light induced photophysical changes of coumarin-540A in ethanol has been studied by the joint applications of X-ray, ultraviolet, and visible spectroscopy. Some impurities were found by X-ray fluorescence measurements. During the high power optical pumping, coumarin showed photochemical changes.

Spectral image analysis for the absorption bands of the beta-methallyl free radical in the vapor phase.

The radicals formed in the flash photolysis of 2-methylbut-1-ene and subsequent reactions have been investigated by kinetic spectroscopy and gas liquid chromatography. Less than 10% of photo products are formed by a molecular made of fission of the excited olefin, and of the radical modes the relative probabilities of band fission, beta(CH):beta(CH):alpha(CC) are 13:1.37:1.

Structure elucidation of cresylviolet perchlorate in polyvinylbutyral by the joint application of IR, FTIR, Raman, UV and visible spectroscopy.

Infrared, Fourier transform infrared, Raman, UV absorption and emission spectra of cresylviolet perchlorate (CV) in polyvinylbutyral (PVB) were recorded in the region 1250-4000 cm(-1) at room temperature and assignments have been made for the observed absorption emission and Raman scattered lines.

Highly sensitive detection of benzyl free radical in the vapor phase.

The 1(2)B(2)-->3(2)B(2) transition in the absorption spectrum of the benzyl free radical has been recorded in the vapor phase together with a new band at shorter wavelengths, probably the first Rydberg band of the radical in the vapor phase. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination.

Theoretical investigations of the specific heat functions for the orthorhombic Nd+3 centers in some crystals.

Garnets doped with Nd+3 have attracted extensive interests because of their applications in solid-state lasers, as well as upconversion luminescence and magneto-optical and magnetic properties. Usually, these properties are closely related to the local structures and properties of the Nd+3 impurities in the hosts. Since information about electronic states and local structures of the impurity Nd+3 in the garnets would be helpful to the understanding of the properties of these materials, theoretical investigations on the specific heat functions and the local structures for these Nd+3 centers are of significance.

Stokes and anti-Stokes Raman scattering of 5H-dibenzo(a,d)cyclohepten-5-ol.

The ultraviolet absorption and emissions as well as Stokes and anti-Stokes Raman scatterings of spectroscopically pure 5H-dibenzo(a,d)cycloheptene-5-ol were investigated by flash and laser-flash photolysis technique in solution at room temperature and at 77K. The whole spectrum, absorption, excitation, prompt and delayed fluorescence, T-T absorption spectra were recorded photographically and photoelectrically in the ultraviolet and visible region and phosphorescence spectrum, Stokes, anti-Stokes scatterings were recorded at 77K.

Structure elucidation of laser dye coumarin-540A by joint application of X-ray diffraction, X-ray fluorescence, prompt fluorescence, UV and visible spectroscopy.

X-ray, ultraviolet, and visible light induced photophysical changes of coumarin-540A in ethanol have been studied by the joint applications of X-ray, ultraviolet, and visible spectroscopy. Some impurities were found by X-ray fluorescence measurements. During the high power optical pumping, coumarin showed photochemical changes.

Sensitized phosphorescence studies of p-xylene+biacetyl system, an optical antenna.

p-Xylene sensitized biacetyl fluorescence and phosphorescence has been investigated and photosensitized phosphorescence lifetimes of biacetyl in the vapor phase has been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, due to primarily, it is believed, to the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature.

Photophysical properties and photochemical rearrangement of single crystal salicylideneaniline in solution.

Salicylideneaniline originally crystallized from a solution has lemon yellow color. Irradiation with near ultraviolet causes the color change from yellow to red. The red state changes spontaneously back to yellow in 2ms.

Specific heat functions for the orthorhombic Nd3+ in scheelite type of crystals.

Nd3+ doped scheelite type of crystals have attracted extensive interests because of their applications in solid state lasers, as well as upconversion luminescence and magneto-optical and magnetic properties. Usually, these properties are closely related to the local structures and properties of the Nd3+ impurities in the hosts. Since information about electronic states and local structures of the impurity Nd3+ in the scheelite crystals would be helpful to the understanding of the properties of these materials, theoretical investigations on the specific heat functions and the local structures for these Nd3+ centers are of significance.

High-resolution discrete absorption spectrum of alpha-methallyl free radical in the vapor phase.

The alpha-methallyl free radical is formed in the flash photolysis of 3-methylbut-1-ene, and cis-pent-2-ene in the vapor phase, and then subsequent reactions have been investigated by kinetic spectroscopy and gas-liquid chromatography. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination. The measured rate constant for the alpha-methallyl recombination was (3.

Triplet-triplet energy transfer from naphthalene to biacetyl in the vapor phase.

In principle the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the different relaxation channels. Initially, electronically excited naphthalene emits photons in the phosphorescence band of naphthalene and these emitted photons are absorbed by the acceptor molecule biacetyl, then excited biacetyl phosphoresces. In this investigation, sensitized phosphorescence decay times in different conditions were measured for naphthalene-biacetyl system in the vapor phase.

Spectral image adaptation and visual experience of DBA/PMMA.

High resolution S0-->Sn and T1-->Tn electronic absorptions and B-type delayed fluorescence of 1,2,7,8-dibenzanthracene in polymethylmethacrylate (PMMA) were experimentally observed by flash and laser flash photolysis technique. Dibenzanthracene (hereafter DBA) molecules were excited in a two-step process. In the first step, an excited singlet is created, which undergoes intersystem crossing to triplet state, then T-T absorption creates an excited triplet dibenzanthracene molecule, which returns to the first excited singlet level by intersystem crossing.

p-Hertz excitation spectroscopy of an optical antenna, optical transmitter-receiver mechanism.

o-Xylene sensitized biacetyl fluorescence and phosphorescence have been investigated and photosensitized fluorescence and phosphorescence lifetimes of biacetyl in the vapor phase have been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, primarily due to, it is believed, the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature.

Radiative electronic energy transfer-time studies of naphthalene-biacetyl system by one and two-photon excitation, and optical antenna mechanism.

In principle, the optical energy absorbed by a complex molecule raises that molecule to one of its excited states, and afterwards this excitation energy decays through the relaxation channels. Initially, electronically excited naphthalene emits photons and these emitted photons are absorbed by the acceptor molecule biacetyl, then excited biacetyl fluoresces. In this investigation radiative energy transfer-time is measured in cyclohexane by one and two-photon excitations.

Photophysical and photochemical study of laser-dye coumarin-481 and its photoproduct in solution.

An ultraviolet light-induced photophysical and Photochemical changes of coumarin-481 in cyclohexane have been studied by photolysis technique at room temperature, due to its potential applications in photonics, photochemistry, and electronic spectroscopy. During the optical pumping, coumarin-481 showed photochemical changes, therefore as the concentration of coumarin-481 decreased, a photoproduct concentration increased rapidly. An absorption band of the product was observed at around 250 nm.