Excitation energies of strontium mono-hydroxide bands measured in flames

Experiments are described to yield more decisive information about the excitation energies of visible strontium monohydroxide bands appearing in flames. Excitation energy differences are derived directly from the ratio of thermal band intensities measured as a function of temperature. Absolute excitation energies are derived from the temperature dependence of the ratio of thermal band to strontium line intensity, while assuming a value for the dissociation energy of SrOH. Flames with temperatures ranging from 1907 to 2886 K were used. A level diagram is proposed for the strontium bands at 6060, 6470, 6690, and 6820 Å. From the results obtained, two conclusions may be drawn: (i) the bands considered are non-resonance bands and (ii) the uncertainty in the excitation energy as a result of the unknown molecular configuration is 0·25 eV.     

Identification of the emitters of some visible alkaline-earth bands in flames

A method is described to identify the emitters (monoxide or hydroxide) of some visible alkaline-earth bands in flames. This method is based on the measurement of the ratio of band to atomic line intensity for a given element in two flames of the same temperature but with a different, known gas composition. In this paper, this method is applied to C₂H₂-air, H₂-air and moist CO-N₂-O₂ and CO-nitrous oxide flames. It appears that in all of these flames the calcium bands found at 5540, 6020 and 6230 Å, and the strontium bands at 6060, 6470, 6690 and 6820 Å are definitely due to the monohydroxide, whereas in the C₂H₂-air flame the barium bands found at 4870 and 5120 Å are due to both oxide and monohydroxide.     

Excitation energies of the giant Gamow-Teller resonance states

The energy difference between the giant Gamow-Teller resonance state and the isobaric analog state is estimated by calculating the energy-weighted and the non-energy-weighted sum of the strengths. The observed energy systematics is well reproduced in a simple model assuming κ_στ ≈ 28 MeV.     

Excitation energy dependence of Raman bands in multiwalled carbon nanotubes

Vertically aligned multiwalled carbon nanotubes (MWCNTs) were grown on 1‐ and 3‐nm cobalt (Co) films, at various growth times by microwave plasma enhanced chemical vapor deposition technique and their microstructural properties were analyzed with the help of Raman spectra that were obtained from different sources of laser excitation energies (E_L: 2.41, 1.96 and 1.58 eV). The variation of D and G band positions in MWCNTs grown on 1‐ and 3‐nm Co films follows a similar behavior, and an anomalous behavior was observed in the E_L dependence of the D′‐band wavenumber. In the second‐order spectra, the G′ band varied strongly according to structure with the laser excitation energy (E_L). The I_D/I_G ratio decreased with the increase of E_L for all MWCNTs; however, for a fixed E_L, the I_D/I_G dispersion is higher at lower E_L. The crystallite sizes were estimated using I_DI_G and E_L. We have shown that, for all MWCNTs, I_D/I_G ratio is inversely proportional to . Copyright © 2010 John Wiley & Sons, Ltd.     

Excitation of a singly charged barium ion in electron-atom collisions

Results of the experimental study of excitation of transitions of singly charged barium atoms in collisions of low-energy monokinetic electrons with barium atoms are presented. Regularities of the behavior of cross sections for excitation in spectral series of BaII are found. The results are compared with other authors’ results.     

Absolute CH concentrations in low-pressure flames measured with laser-induced fluorescence

Laser-induced fluorescence in both theA–X andB–X band systems was used to measure absolute number densities of CH radicals in 40 Torr propane/air flames at temperatures near 1600 K. The fluorescence signal was calibrated against Rayleigh scattering in N₂ and Raman scattering in H₂. In a rich flame, = 1.15, the concentration at the peak of the CH distribution was 5.8 ± 1.5 ppm, or (1.4 ± 0.4) × 10¹² cm^–3, with independent values obtained using both band systems and calibration methods in good agreement. This result compares well with a prediction of 8 ppm from a kinetic model of this flame.     

Effect of oxygen on CN bands emitted from active nitrogen flames

O₂ and C₂H₂ are added to the reacting N₂ afterglow + C₂H₂ which emits intense CN bands. The resulting changes in the spectra are examined. The results are presented and explained on the basis of C + O₂ → CO + O and N + O₂ → NO + O.     

The nature of absorption bands in zinc oxide

Results are offered from a study of ultraviolet absorption in ZnO in its original state, after reduction, and light action as a function of time for which irradiated specimens are maintained in a vacuum and in the atmosphere. Bands at 3.36, 3.28, 3.21, 3.15, and 3.02 eV were detected, and the kinetics of change in their intensity with duration of light action are interpreted.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 32–36, July, 1985.The author expresses his gratitute to M. I. Dvoretskii for participation in the experimental studies.     

Ionic conductivity of gadolinium-doped barium praseodymium oxide

To clarify the ionic conduction of Ba(Pr_0.6Gd_0.4)O_3−α, the electrical conductivity was measured in moist air and hydrogen atmospheres. The ionic transport number was estimated by a steam concentration cell, a hydrogen permeation cell, and a fuel cell. Temperature dependence of the conductivity in a moist air atmosphere differed from that in a moist H₂ atmosphere. The conductivity under reducing conditions increases with time according to the crystal structure change of Ba(Pr_0.6Gd_0.4)O_3−α due to oxygen loss in the lattice site. Under moist air conditions, the dominant conduction species in the Ba(Pr_0.6Gd_0.4)O_3−α electrolyte were mainly holes. However, the species changed into proton, oxide ion and hole by means of structure change in a reducing atmosphere. It was considered that the ionic conduction occurred due to the crystal structure change. It was predicted that this peculiarity of the conductivity of barium praseodymium oxide influenced the nonstoichiometric behaviour of Pr in the crystal structure.     

Correlation of inner shell binding energies with shifts of charge transfer bands

Inner shell binding energies were determined for the elements in the crystalline compounds A^IIIX^VO₄ where A  B, Al, Ga, Fe and X  P, As with fourfold coordination of A, and in the corresponding dihydrates of Al having a sixfold coordination of Al. The O 1s binding energies for the dihydrates could be resolved into two bands arising from XO₄ -groups and from the water molecules respectively. The O 1s binding energies from the XO₄ groups decrease by about 0.6 eV in going from the anhydrous compounds to their dihydrates whereas the Al 2p binding energies remain constant within the limits of error. These results correlate surprisingly well with shifts of the first charge transfer band of trivalent iron in these compounds. The binding energy differences between phosphates and arsenates are also in good agreement with concurrent shifts of this charge transfer band. The consequences of these results for the concept of optical electronegativities are discussed.     

Barium/barium oxide dispensation rate measurement

A quantitative knowledge of the Ba/BaO dispensation rate is necessary in order to understand the physics and chemistry of dispenser cathode surfaces, and the consequent cathode activity. This paper discusses three devices for determining Ba/BaO evaporation rate: the quartz crystal microbalance, the quadrupole mass spectrometer, and the Becker diode. An improved Becker diode technique is described which eliminates the drawbacks of the classical methods, and therefore may be suitable for routine use.     

Excitation energies of particle-hole states in 208Pb and the surface delta interaction

The schematic shell model without residual interaction (SSM) assumes the same excitation energy for all spins in each particle-hole configuration multiplet. In ²⁰⁸Pb, more than forty states are known to contain almost the full strength of a single particle-hole configuration. The experimental excitation energy for a state with a certain spin differs from the energy predicted by the SSM by ?0.2 to +0.6 MeV. The multiplet splitting is calculated with the surface delta interaction; it corresponds to the diagonal matrix element of the residual interaction in the SSM. For states containing more than 90% strength of a certain configuration and for the centroid of several completely observed configurations, the calculated multiplet splitting often approximates the experimental excitation energy within 30 keV. The strong mixing within some pairs of states containing the full strengths of two configurations is explained.     

Excitation of photoluminescence in Er-doped oxide and fluoride crystals

It has been established that laser excitation of infrared radiation (2.9 μm) in oxide and fluoride crystals doped by Er³⁺ ions gives rise to excitation of concomitant luminescence in the visible region according to the two-step nonlinear mechanism.     

Absorption bands of intrinsic point defects in irradiated zinc oxide

A program has been developed for separating the spectrum of radiation-induced absorption in powdered zinc oxide and reflective coatings based on it into individual components which includes calculations of the parameters of the bands arising from intrinsic point defects, bands from chemisorbed gases, and nonelective absorption by free electrons. Experimental results on the changes in the diffuse reflection spectra of ZnO powder and reflective coatings after the action of various forms of radiation have been found. The experimental spectra have been decomposed into individual components. Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 106–112, September, 1997.