Method Of Kinetic Spectroscopy Research Articles

Диссоциативная рекомбинация молекулярных ионов Ne-=SUB=-2-=/SUB=--=SUP=-+-=/SUP=- с электронами. Заселение атомов конфигурации 2p-=SUP=-5-=/SUP=-4p в распадающейся плазме

The paper presents the results of the study of decaying neon plasma by the method of kinetic spectroscopy. Experimental conditions: neon pressure 0.2–152 Torr, electron density in the initial stage of decay [e] ≤ 5 × 1010 cm-3. The plasma was created by a pulsed barrier discharge with electrodes on the outer surface of a cylindrical glass tube. Discharge frequency 40–160 Hz. On the basis of a comparative analysis of the dependences of the intensities of spectral lines on the time and temperature of electrons in the afterglow, it was shown that in terms of the mechanisms of population, the levels of 2p54p are clearly divided into two groups. Lower levels: from 3p10 to 3p3 (Paschen notation) are associated with the dissociative recombination of molecular ions with electrons and, up to pressures of 0.6 Torr, the lines emitted by them behave identically to the lines of 2p53s ← 2p53p and 2p53p ← 2p53d transitions. The behavior of the upper levels (3p5, 3p2, 3p4, and 3p1) was more complex, and at low pressures, the populations of all 2p54p levels turned out to be related to the impact-radiation recombination of Ne + ions. Significant differences in the dependences of the relative populations of 3d and 4p levels on the neon pressure are discussed.

SPECTRAL KINETIC METHOD AND ITS APPLICATIONS IN THE EVALUATION OF GABAPENTIN

Context: A new and highly sensitive method for the determination of gabapentin (GBP), this method is of high importance in the assessment of GBP and other pharmaceutical preparations. GBP is a widely used antibiotic. There is a big challenge of analysis of anti-epilepsy drugs due to their instability and sensitivity to various conditions. The simple, sensitive, precise, and kinetic spectroscopy method was used to measure GBP in some pharmaceuticals developed and validated. Objective: The objective of the study was to develop a simple, sensitive, accurate, and kinetic spectroscopy method for the measurement of GBP in a pharmaceutical product. Materials and Methods: The current method was based on the spectral kinetic examination of epileptics (GBP) with potassium permanganate in alkaline medium at room temperature. Absorption of the stained manganese ions of the product was absorbed at 605 nm. Results: The concentration of GBP was calculated using the calibration equation for the time method and the initial rate method. The above method is used to determine GBP from 2.0 to 20 μg/mL. The BER Act was applied to roads within the range of concentrations used for analysis. The limit of quantification and limit of detection, equal to 0.640 and 1.940, were calculated, respectively. The relative standard deviation values was found to be 0.345% and Recovery values were 99.38 and 0.50%, respectively. Conclusion: The proposed and developed method is sensitive, accurate, and tolerable and can be used for the routine analysis of GBP in various pharmaceuticals. The proposed method was successfully applied to the determination of the drug jabapentin in the pharmaceuticals and the validation of the statistical data. The results were compared to the reference method showed good compatibility.

Spectral-Luminescent Properties of Alkoxysilane–Metallophthalocyanine Conjugates Covalently Bonded to the Polymeric Chains of Silicate Gel Materials

Conjugates of metal hydroxyl phthalocyanines (М(ОН)nРс; М = Si, Ge, Al, Ga) with 3-aminopropyltriethoxysilane (APTEOS) are synthesized. By means of the sol-gel method, polymeric silicate gel materials doped with the (APTEOS)n–М(ОН)nРс conjugates are prepared: the latter form structural links in the composition of the copolymer with the siloxane fragments of the polymeric chains (in the case of n = 2) or are ″grafted″ to such chains in the form of side substituents (n = 1). It is shown by spectral-luminescent and kinetic spectroscopy methods that the (APTEOS)n–М(ОН)nРс conjugates, on the introduction into a silicate gel material, retain their molecular structure and the photophysical characteristics of MPc in the monomeric form. The obtained macromolecular substances are promising as monomeric dopants in new functional materials for optics and quantum electronics.

Erratum to: “Luminescence self-quenching in praseodymium-doped double sodium-yttrium fluoride cubic crystals (Na0.4Y0.6F2.2:Pr3+)”

Energy transfer processes between praseodymium dopant ions, which are responsible for the luminescence self-quenching in crystals Na0.4Y0.6F2.2:Pr3+ (NYF:Pr3+; Pr = 0.4–9%), have been investigated experimentally and theoretically. Using methods of kinetic spectroscopy with selective excitation, the praseodymium luminescence decay kinetics from the levels 3 P 0,1 and 1 D 2 selectively excited by nanosecond laser pulses has been studied. Based on model quantum-mechanical calculations, interionic interaction microparameters have been determined theoretically and mechanisms that are responsible for the interaction of praseodymium ions by particular most likely energy transfer schemes have been elucidated. Energy transfer macrorates (of migration and quenching) have been found, and the values obtained have been used as parameters for calculation of the decay dynamics of the excited 1 D 2 and 3 P 0,1 levels of praseodymium ions. It has been shown that luminescence self-quenching from the 1 D 2 level in NYF:Pr3+ crystals can be described well in terms of the model of static ordered decay in the presence of dipole-dipole and dipole-quadrupole interactions. The luminescence self-quenching from the 3 P 0,1 levels is mainly determined by the dipole-dipole interaction, and it also can be described in terms of the model of the static ordered decay. Good agreement has been obtained between experimental and calculated kinetic dependences that characterize energy transfer processes in NYF:Pr3+ crystals in relation to the concentration of doping ions. Based on the obtained data, it has been concluded that investigated crystals of a certain composition are promising for use in quantum electronics and optical converters.

Spectroscopic characteristics of praseodymium-doped cubic double sodium-yttrium fluoride crystals Na0.4Y0.6F2.2:Pr3+. Intensities of optical transitions and luminescence kinetics

Using the Bridgman-Stockbarger technique, we have grown a series of cubic crystals Na0.4Y0.6F2.2:Pr3+ (NYF:Pr3+) with a content of praseodymium in the range of 0.04–9 at %. We have determined the composition of crystals, evaluated their optical quality, and found the incorporation coefficient of Pr3+ ions into the Na0.4Y0.6F2.2 matrix (K Pr ∼ 0.9). We have examined optical spectra of NaYF:Pr3+ crystals at room and low (7 K) temperatures in the range of 200–2500 nm. The low-temperature absorption spectra of NYF:Pr3+ crystals have been shown to consist of broad weakly structured bands. Based on the analysis of low-temperature absorption spectra, the structure of the Stark splitting of praseodymium levels has been represented in terms of a model of “quasi-centers,” which are characterized by an inhomogeneous broadening of Stark components. From experimental absorption cross-section spectra at T = 300 K, we have calculated oscillator strengths for transitions from the ground state 3 H 4 to excited multiplets 3 H 5, 3 H 6, 3 F j (j = 2, 3, 4), 1 G 4, 1 D 2, and (3 P j ,1 I 6) (j = 0, 1, 2). Using the Judd-Ofelt method, we have determined intensity parameters Ω t and found that Ω2 = 0, Ω4 = 4.4 × 10−20, and Ω6 = 2.28 × 10−20 cm2. With these values, we have calculated the probabilities of radiative transitions, the branching coefficients, and the lifetimes of the radiative levels 1 D 2 and 3 P 0. The probabilities of multiphonon nonradiative transitions in NYF:Pr3+ crystals have been estimated. Using the method of kinetic spectroscopy with selective excitation, we have investigated the luminescence decay kinetics of praseodymium from the 3 P 0 and 1 D 2 levels upon their selective resonant excitation by nanosecond laser pulses. The inference has been made that Na0.4Y0.6F2.2:Pr3+ crystals are processable; admit doping by praseodymium in high concentrations; and, with respect to all their radiative characteristics, can be potentially considered as active media for converters of optical radiation and solid-state continuously tunable lasers in the visible range.

Determination of the dynamics of microcharacteristics of solutions by time laser spectroscopy

The development of simple methods used to analyze the available data and separate the contributions from the main physicochemical processes responsible for the kinetics of instantaneous emission spectra is of considerable interest due to the intensive investigation of the time-resolved characteristics of fluorescence of various quantum objects that are used to examine the most important photophysical and photochemical reactions in excited states. The relation between the functions of the shift in the instantaneous spectra of spontaneous emission of molecules (obtained using kinetic spectroscopy methods) and the time variations in the configurational structure of solvates, as well as the charge transfer in the excited singlet state of molecules of the luminescent probe, has been shown using simple analytical expressions of solvatofluorochromism. The fluorescence of solutions of one of the most important molecular probes, namely, 1-(phenylamino)naphthalene in glycerol, has been investigated with a picosecond time resolution. This molecular probe is known because its electric dipole moment is formed in the excited singlet state, which almost instantaneously initiates processes of intermolecular rearrangement of solvent molecules. It has been demonstrated that it is possible to determine the time dependence of the function of the dielectric response of the polar solvent to the dipole of this probe and, hence, the time evolution of the microcharacteristics of the solvent that determine the above function.

Influence of secondary processes on the quantum yield of I(2P1/2) atoms formed by photolysis of iodides measured by a kinetic spectroscopy method

Numerical calculations of the kinetics of secondary processes occurring during photolysis of iodides (RI) are made using published values of the rate constants. It is shown that in the case of insufficient time resolution and a large number of photolysis-inducing pulses these processes may have a considerable influence on the relative values of the quantum yield OI*rel(λ) measured by kinetic spectroscopy methods. A report is given of measurements, under conditions avoiding the influence of such secondary processes on OI*rel(λ), of the values of this yield at λ = 266 nm for the following iodides RI:CF3I, C2F5I, C3F7I, CF3CFICF3, C4F9I, (CF3)3CI, CH3I, C2H5I, C3H7I, and CH3CHICH3. The rate constants of deactivation of I(2P1/2) atoms by alkyl iodide molecules are determined.

Applications of Lasers to Kinetic Spectroscopy

Three methods of kinetic spectroscopy using lasers are described. In the first, the infrared double resonance technique using two CO2 lasers has been used to examine the relaxation of both 11BC13 and 10BC13. The relaxation of the initially excited state to a distribution of excited states proceeds by a very fast V-V process at a rate of at least 2 x 10 6 sec-1 torr-1. The rates of deactivation of BC13 by the rare gases, HC1, DC1, H2, HD, D2, N2, CH3F, and CHC13 have been measured and indicate that rotational degrees of freedom in the collision partner play an important role in deactivation. Two other applications of lasers to kinetic spectroscopy will be described. A Q-switched CO laser is used to excite CO to its first vibrational level and subsequent relaxation of CO by D2CO is monitored by following the CO fluorescence. In another application, a nitrogen laser is used to dissociate H2 CO and the time-evolution of specific states of the CO produced is monitored by the absorption of CO laser light.

Gas phase absorption spectra and decay of triplet benzene, benzene- d6, and toluene

Transients formed when benzene and toluene are excited by energy transfer from Hg( 3P 0) atoms were investigated by a modulation type kinetic spectroscopy method. Broad transient absorption bands were observed with maxima at 231.5 nm for benzene and 240.0 nm for toluene. Their oscillator strength was estimated to be 0.06. These absorptions were attributed to the hydrocarbon triplet state and assigned to the 3E + 2g - 3B − 1u electronic transition of benzene. Kinetic measurements indicated that the decay of the triplet state is not determined by a unimolecular process. Liftimes as long as 0.5 msec were observed and could be explained as due to impurity quenching. Lifetime shortening at higher triplet formation rates occurred in a way consistent with an extremely rapid triplet-triplet bimolecular process. Secondary transients were observed in each hydrocarbon, and identified as triplet biphenyl in the case of benzene.

Deactivation of excited iodine atoms I(52P½)

Electronically excited (5p2P½) and ground state (5p2Pz.frac32;) iodine atoms, resulting from the flash photolysis of trifluoromethyl iodide, have been monitored in absorption in the vacuum ultra-violet region of the spectrum by the method of kinetic spectroscopy. A long-lived population inversion can be observed in the absence of laser action when argon is the added gas. Under these conditions, the rate of decay of I(52P½) is very slow so that deactivation by other added gases can be studied conveniently, particularly as the optical transition to the ground state is electric dipole forbidden. In argon the rate of decay of the excited iodine atoms increases with decreasing pressure although the absolute magnitude of the rate is some 5-6 times that calculated according to the Chapman-Enskog equation for the diffusion of xenon in argon. For N2 and C3H8, the decay exhibits first-order kinetics for these gases and is independent of the pressure of added argon. No significant contribution to the removal of I(52P½) by a hydrogen-atom abstraction reaction with propane was observed. No significant deactivation by CF3I itself was observed. The collision efficiencies for the deactivation of I(52P½) by the gases N2, C3H8 and I2(from a previous investigation) are found to be 3.0 × 10–6, 3.2 × 10–4 and 7.2 × 10–2, respectively.

The combustion of hydrogen sulphide studied by flash photolysis and kinetic spectroscopy

The combustion of hydrogen sulphide has been investigated by the method of kinetic spectroscopy and flash photolysis. If no large excess of inert gas is present the reaction produces sulphur dioxide. The reaction has been shown to take place in steps in which the radicals SH and OH participate. Simultaneously with the appearance of the sulphur dioxide; a light emission has been observed which is attributed to the process: SO + O→SO2 + hv . In the presence of a large excess of inert gas the reaction results in S 2 O 2 . It has been shown that the formation of S 2 O 2 is favoured by a low temperature. Flash photolysis of hydrogen sulphide, sulphur dioxide and S 2 O 2 has also been investigated. In the last two cases the absorption spectra disappear temporarily. Inert gas prevents the disappearance of the SO 2 , but not that of S 2 O 2 . From an analysis of our results a mechanism for the combustion of hydrogen sulphide is derived and discussed.